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S.R.P* 5 TH TERM- CONSTRUCTION EQUIPMENT MANAGEMENT Page 1 CLASSIFICATION OF MAJOR EQUIPMENT Construction equipment classification facilitates identifying equipment, verifying stock, locating spares, recording repairs, accounting costs, indexing catalogues, logging performance, monitoring effectiveness, estimating outputs, and planning procurements. There are many methods for classifying construction equipment. These include dividing the equipment into special purpose and general purpose machines; classifying equipment according to the alphanumeric code generally, conforming to the description of equipment; and categorizing equipment into its functional use. In particular, functional classification of major equipment is reflected in below: Functional Classification of Construction Equipment 1.Earthwork Equipment Excavation and lifting equipmentback actor (or backhaul, face shovels, draglines, grata or clamshell and trenchers. Earth cutting and moving equipmentbulldozers, scrapers, front-end loaders Transportation equipmenttippers dump truck, scrapers rail wagons and conveyors. Compacting and finishing equipmenttamping foot rollers, smooth wheel rollers, pneumatic rollers, vibratory rollers, plate compactors, impact compactors and graders. 2. Materials Hoisting Plant Mobile cranescrawler mounted, self-propelled rubber-tired, truck-mounted. Tower cranesstationary, travelling and climbing types. Hoistsmobile, fixed, fork-lifts. 3. Concreting Plant & Equipment Production equipment-batching plants, concrete mixers. Transportation equipmenttruck mixers, concrete dumpers Placing equipmentconcrete pumps, concrete buckets, elevators, conveyors, hoists, grouting equipment. Precasting special equipmentvibrating and tilting tables, battery moulds, surface finishes equipment, prestressing equipment, GRC equipment, steam curing equipment, shifting equipment. Erection equipment. Concrete vibrating, repairing and curing equipment, Concrete laboratory testing equipment. 4. Support and Utility Services Equipment Pumping equipment. Sewage treatment equipment. Pipeline laying equipment. Power generation and transmission line erection equipment. Compressed air equipment. Heating, ventilation and air-conditioning (HVAC) equipment. Workshop including wood working equipment. 5. Special Purpose Heavy Construction Plant

5th Term - Construction Equipment Management

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Page 1: 5th Term - Construction Equipment Management

S.R.P* 5TH TERM- CONSTRUCTION EQUIPMENT MANAGEMENT Page 1

CLASSIFICATION OF MAJOR EQUIPMENT

Construction equipment classification facilitates identifying equipment, verifying stock, locating

spares, recording repairs, accounting costs, indexing catalogues, logging performance, monitoring

effectiveness, estimating outputs, and planning procurements. There are many methods for

classifying construction equipment. These include dividing the equipment into special purpose and

general purpose machines; classifying equipment according to the alphanumeric code generally,

conforming to the description of equipment; and categorizing equipment into its functional use. In

particular, functional classification of major equipment is reflected in below:

Functional Classification of Construction Equipment

1.Earthwork Equipment

Excavation and lifting equipment—back actor (or backhaul, face shovels, draglines, grata

or clamshell and trenchers.

Earth cutting and moving equipment—bulldozers, scrapers, front-end loaders

Transportation equipment—tippers dump truck, scrapers rail wagons and conveyors.

Compacting and finishing equipment—tamping foot rollers, smooth wheel rollers,

pneumatic rollers, vibratory rollers, plate compactors, impact compactors and graders.

2. Materials Hoisting Plant

Mobile cranes—crawler mounted, self-propelled rubber-tired, truck-mounted.

Tower cranes—stationary, travelling and climbing types.

Hoists—mobile, fixed, fork-lifts.

3. Concreting Plant & Equipment

Production equipment-batching plants, concrete mixers.

Transportation equipment—truck mixers, concrete dumpers

Placing equipment—concrete pumps, concrete buckets, elevators, conveyors, hoists,

grouting equipment.

Precasting special equipment—vibrating and tilting tables, battery moulds, surface finishes

equipment, prestressing equipment, GRC equipment, steam curing equipment, shifting

equipment.

Erection equipment.

Concrete vibrating, repairing and curing equipment,

Concrete laboratory testing equipment.

4. Support and Utility Services Equipment

Pumping equipment.

Sewage treatment equipment.

Pipeline laying equipment.

Power generation and transmission line erection equipment.

Compressed air equipment.

Heating, ventilation and air-conditioning (HVAC) equipment.

Workshop including wood working equipment.

5. Special Purpose Heavy Construction Plant

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Aggregate production plant & rock blasting equipment

Hot mix plant and paving equipment.

Marine equipment.

Large-diameter pipe laying equipment.

Piles and pile driving equipment,

Coffer dams and caissons equipment.

Bridge construction equipment.

Railway construction equipment.

9.2 EARTH FACTOR IN EARTHWORK

The most important factor that determines the suitability of equipment for earthwork is the earth itself.

The earthwork process is affected by the ground condition. The main ground characteristics which

influence the performance of the equipment are the suitability of equipment, the digging effort, the

resulting output, and the output measurement.

9.2.1 Equipment Suitability

The type of earthmoving equipment required varies with the nature of the soil and tasks to be

performed. Typical job-related equipment used in building projects are given below:

(1) Excavating and lifting in soft earth

(a) Deep pits excavation — Clamshell and dragline.

(b) Shallow pit excavation — Backhoes.

(c) Ground level excavation — Shovels.

(d) Shallow trenching — Trenchers, excavators (backhoes).

(e) Wet soil excavation — Excavators (dragline or) grab.

(2) Cutting: over areas

(a) Short-hauls

(b)Long-hauls

(3) Loading and transporting excavated soil

(a)Loading soil — Loaders, shovels, excavators.

(b)Transporting soil — Tippers, dumpers, scrapers. rail wagons, conveyors.

9.2.2 Digging Effort

The digging effort of equipment depends upon the nature of the soil. For example, it is easy to dig in

common earth than in stiff clayey soil. The typical soil factor which determines the

comparative equipment effort required in various types of

soils can be taken as under

Nature of soil

Loam, sand, gravel Common earth Stiff clay, soft

rock

Digging effort

Easy digging Medium digging

Hard digging

Soil

factor

1.0

0.85

0.67

Volume Conversion of Soil brio its Three States

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9.2.3 Volume Conversion

The volume measure varies with the state

of the soil. Three states of soil encountered

in earthmoving operations are in-place

natual soil, loose excavated bulk soil, and compacted soil. The volume of soil in its in-place natural

state is usually, referred to as the bank volume. It swells when heaped in a loose state after

excavation, and shrinks when mechanically compacted.

9.2.4 Equipment Output

The equipment capability to perform an assigned earthwork task can been be determined from the

on-site actual trials or can be accessed from its past performance records of

Operation under similar site conditions

The equipment's hourly output is determined by multiplying the earth quantity moved

(Load) per cycle by the number of cycles per hour

Equipment actual hourly output = Actual load/cycle x cycles/hour

For example, a front-end loader on a given job moves a load of 1.5 m3 of loose soil in one cycle

consisting of loading-lifting-travelling-unloading-return trip-sod ready for loading. If each cycle time is

1.2 minutes, then

Actual output per working hour = Load per cycle x cycles per hour

« 1.5 m3 * 60 minutes/1.2 minutes = 75 m3 per hour.

But at the planning stage the actual on-site trials may not be feasible, and the past performance

data may not always be available, or it may not be adequate as the site conditions vary from place to

place and project to project. In the absence of these reliable performance methods, the equipment

output norms can be derived from the performance data given in the manufacturer‘s manuals. This

off-the-job equipment hourly ideal output data is reflected in these manuals in the form of charts,

graphs, performance curves, and tables. This 'ideal output' is multiplied by 'correction factor' to

determine the optimum output1.

Optimum output = Ideal output x Correction factor.

Correction factor depends upon the operating characteristics of the equipment and the site

conditions like excavator swing factor, earth grade factor, soil factor, rolling resistance, traction factor,

and so on. The ideal output and correction factor are covered in subsequent paragraphs under each

equipment.

The equipment planned performance at site of work depends upon many situational factors that

influence the output. These situational factors can be broadly grouped under two headings, i.e.

controllable factors and uncontrollable factors. The output adopted planning purposes can be

determined as under:

Planned output = Optimum output x Performance factor.

Nature of soil Bank volume Loose volume Compacted volume

Common earth Sand Clay Rock (blasted)

1.00 1.00 1.00 1.00

1.25 1.12 1.27 1.50

0.90 0.95 0.90 1.30

.....................

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9.3 EARTH EXCAVATING EQUIPMENT

Primary earth excavating equipment is the tractor-mounted excavator. Excavators operate in a

stationary mode. They dump excavated materials on the sides, or directly into waiting tippers/dump

trucks and they gradually, shift their position as the work progresses. Various types of earth

excavating equipment are listed in Exhibit 9.2.

The excavating equipment is divided into four categories, viz. face shovels, backhoes, draglines

and grab or clamshell Further, excavators can be rope-operated or hydraulically . Operated the type

and size of the equipment depends upon the nature of the task, the type of soil, digging depth and

the desired level of production.

9.3.1 Face Shovel

It operates from a flat surface, producing upward digging action, excavating

and filling the bucket as it climbs after the bucket is filled, its upper part swings

to the dumping position where the bucket is emptied in a waiting truck or on to

a stockpile. Thereafter, it returns to its original position and starts the next cycle

of excavation. It is capable of working in all types of dry soils. The struck-

bucket capacity of the face shovel bucket varies from VI yd! (0.38 wft to 4/1/2 yd* (3 25 to3), and

depending upon the size of the machine and bucket, its cutting length varies from 7 m to 10. 6 m

9.3.2 Backhoe

It is primarily used for excavating materials below its track level, i.e. excavation

of small end Urge pits, bison* net and large trenches, backhoe are generally

track-mounted but snail capacity equipment do have wheel-mounting to add to

their mobility.

The backhoes are fitted with buckets having struck capacity varying from 1/2 Yd' (0.38 m) to 4 1/4

Yd3 (3.25 m9) and their corresponding digging depth capability is from 5 m to a maximum of 9.5 m.

9.3.3 Dragline

It is a rope-operated boom-fitted crane type machine. The bucket is thrown into the

excavation area, and the cable-controlled hook is rotated, so that, the bucket gets

filled by scraping the surface to be excavated. It is used for digging below the

ground level specially, in loose soils or marshy and underwater areas with soft

beds.

The dragline can operate in a depth approximately up to 1/3 of its boom length for broad sweeping

type excavated work. Its boom length varies from 21 m to 36 m and the struck bucket capacity

extends from 1/2 Yd3 (0.38 m3) to 4 Yd3 (3.06 m3).

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9.3.4 Grab or Clamshell

Like dragline, it is a rope-operated boom-fitted crane type machine having a

grab or clamshell bucket the grab bucket has interlocking teeth to penetrate

loose soil whereas the clamshell bucket has no teeth. These buckets are

dropped with their sides open like open jaws on the soil to be grabbed, and

thereafter, these jaws are closed by rope machines prior to hauling. These

machines are used primarily for deep confined excavations such as shafts, wells and spoil heaps

removal. The depth of the excavation can be roughly taken as 1/3 of the boom length. The range of

the size of the grab bucket and its length of boom are similar to those of the dragline.

9.3.5 Output Planning Data

Planned output = Ideal output x Correction factor x Performance factor.

‗Ideal output in loose cubic meters (LCM):\

Ideal output = Bucket output/Cycle x Cycles/hour these are explained as under;

(a) Bucket output/cycle—a cycle of a bucket starts from the point it strides the excavation place to its

return to the next excavation point after unloading the excavated materials at the specified place in

the transporter or on a heap of loose excavated materials. The maximum loose material in cubic

meter* (LCM) it can carry in its bucket per cycle is equal to its bucket struck capacity.

(b)Cycles/hour—the cycle time is the time taken by the cycle of bucket movements which includes

load, swing, unload and return to start the cycle again.

Maximum number of cycles/hour * 60 minutes/cycle time in; minutes.

9.3.6 Correction Factors

These include the following and their implications on the equipment output are shown in

Excavator Output Adjustment Factors for Secondary Tasks

Equipment Nature of Secondary Tasks Task Efficiency

Shovel Movement from excavating place to unloading place:

a. Within vicinity 1.0

b. Little movement 0.6 to 0.9

c. Appreciable; movement or delays 0.4 to 0.6

Backhoe Trenching

a. Equal to bucket width 1.0

b. More than bucket width 0.7 to 0.9

Dragline a. Bulk excavation 1.0

b. Wide open ditches 0.7 to 0.9

c. Confined, restricted places 0.5 to 0.7

Clam shell a. Dry soil Pits 0.9

b. Wet soil pits 0.5 to 0.9

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(a) Equipment conversion factor: It relates to the type of equipment employed.

Equipment Factor multiplier

Face shovel 1.00

Backhoe 0.80

Dragline 0.75

Grab 0.40

(b)Soil digging factor: It depends upon the digging effort. Digging

effort Factor multiplier

Easy digging

Medium digging

Hard digging

9.3.7 Procedure for Determining Output from Equipment Output

Planning chart the output of an excavating equipment, for planning purposes, can be easily

determined from the equipment output planning table shown in Appendix 9.1. The procedure involved

is explained with the following example:

Example Estimate the hourly production in bulk volume (LCM) of a backhoe with bucket capacity of

0.96 M3 employed on excavation of a foundation four meters deep in hard digging soil. The excavated

earth is to be loaded in waiting dump trucks, placed at a swing angle of 75 degrees. The expected

performance efficiency is 83%.

(a)Ideal output of loose soil in cubic meter (LCM) for an

equivalent face shovel of bucket capacity of 0.96 m3 from

Appendix 9.1.

(b)Backhoe output using equipment conversion factor of 0.8

operating at optimum depth

(c)Correction factors applicable are

—Soil factor for bard digging = 0. 67

—Load factor for loading into vehicle = 0.80

—Swing factor for 75 degrees = 1.05

Therefore, correction factor

s 0.67 x 0. 80 x 1.06

(d) Performance efficiency Hence expected output/h

= Ideal output x correction factor x performance efficiency.

= B x C x D » 0.8A x C x D = 120 x 0.56 x 0 . 83 Say = 56 LCM/h.

1.0

0

0.8

5

0.6

7

= 150 LCM (approximate)

= A x 0.80 = 120 LCM

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9.4 EARTH CUTTING AND HAULING EQUIPMENT

9.4.1 Bulldozers

The bulldozer is a versatile machine. It can be used for moving earth

over distances upto 100 m, clearing and grubbing sites, stripping top

unwanted soil, excavating to a shallow depth say upto 200 mm at a

time, pushing scrapers, spreading soil for leveling areas, ripping bare

soft rock, and maintaining roads. Bulldozers normally are Track-

mounted, however there are four-wheeled dozers with large-powered

engine. The wheel dozers exert higher bearing pressure as compared

to track-dozers.

Dozers excavate and push earth with the help of a stiff welded steel blade fitted in front and

controlled by two hydraulic cylinders. Blades are of four types. The straight S-blade is used for

forward pushing of earth. U-blades have large capacity, and are used for pushing loose materials.

Angle A-blades are used for pushing soil to one side rather than hauling it forward as is required in hill

road formation cutting. Push P-blades are used for push loading a scraper. A dozer can also be fitted

with a backhoe attachment for ripping hard soil and rock, and a winch for uprooting trees, skidding

boulders and heavy materials.

Ideal output for dozing soft soil depends upon the engine power, straight-blade capacity and dozing

distance. The ideal output of bulldozers is shown in Appendix 9.1.

This ideal output, measured in the bulk volume (loose soil), assumes forward dozing speed of 3

km/h, return speed of 6 km/h, maneuvering time of 0.15 minutes, easy going on generally level

ground and dozing of (bank) materials using a straight S-blade. This ideal production is corrected to

conform to varying conditions as under.

Dozer optimum output = Dozer ideal output x Correction factor

Output planning data = Dozer optimum output x performance factor

Where, correction factor leads to the following effect.

(a) Blade factor—multiply ideal output by the blade factor value.

Type of blade Blade factor

S blade 1.0

A blade 0.75

U blade 1.25 (used only for loose soil).

(b) Transmission system—For direct drive, take 80% of the ideal output which is based on the

power shift system. Direct drive system output = 0.8 power shift system

output.

(d)Grade factor—The manufacturer's manual provides the data for a change of output with varying

slope, but for planning purposes it can be taken as under.

(e)Nature of slope Effect on output (%)

(f) Downhill working Increase 2.5 x grade (%)

(g)Uphill working Decrease 2 x grade (%).

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Example Determine the output of a bulldozer having 215 HP engine, fitted with . blade rated capacity

4.40M . The dozer is employed for excavating a hard clayey arc

with average haulage of 50 meters, on a ground with down slope of 10%. It has dire drive

transmission, and its expected performance is 50 minutes per hour.

Solution Output/h = Ideal output/h x correction factor x performance factor.

(a) Ideal output/h for 50 meter haulage of

215 HP dozer with 'S' blade of capacity ... , „, .

A A-T, _3 r _ A- _ j _ « , * 160 LCM approximate)

4.40 m from Appendix 9.1.

(b) Correction factors applicable ore:

—Soil factor for hard digging = 0.67

—Blade factor for A blade ■ 0.61

—Grade factor for 10 % down grade = 1 + 2.5 x 10%

(assistance) = 1-25

—Transmission factor for direct drive = 0.8

—Swell factor of clayey soil = 1.3

Therefore correction factor

= 0.67 x 0. 65 x 1. 25 x 0. 8 x ^ = 0.42

(C) Performance factor for 50 min/hour working = 0.83

(D)Therefore expected output in BCM = AxBx C

= 160 x 0.42 x 0.83 = 55.8. Say 56 BCM

9.4.2 Scraper

It is the equipment commonly used for scraping, loading,

hauling and discharging including spreading large quantities of

earth over long distances; say around three Km. It can scrape

soils in layers of 15 cm to 30 cm in depth. Basically, a scraper has a soil container or bowl mounted

on two wheels. It digs into the earth after the forward portion of the container is lowered, and it

collects the earth as the scraper moves forward. Unloading and spreading takes place in controlled

layers in the discharge area with the aid of a tractor plate while the unit keeps on moving. Scrapers

come in many sizes varying from 8m3 to 50 m3. There are two main categories of scrapers—(I) towed

scrapers and (ii) motorized scrapers. They are shown in Exhibit 9.4.

(I) Towed scrapers these are pulled by a tractor or a bulldozer capable of 300 HP or more. Although

the loading cycle may take hardly two to three minutes, its travelling speed is slow. Its main

advantage over the motorized scraper is that it can operate in small areas

And can scrape in heavy soil areas. Towed scrapers are best suited for medium distances

Up to 400 m. Towed scrapers range from 8 m3 to 30 m3.

(If) Motorized scrapers Several types of motorized scrapers with heaped capacity ranging from 15

m3 to 50 m3 are available to suit varying job requirements. These include single engine scraper,

double engine scraper and elevating scraper.

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(a) Single engine scraper requires a pusher bulldozer to provide the necessary attractive force.

Generally one medium-sized crawler tractor is sufficient to serve four to five scrapers.

B , Cycle time of each scraper

Scrapers per pusher = ■ ~ ? -- R—-—

Cycle time of pusher

Example Cycle time of a scraper is 6 minutes and a pusher to fill a scraper is 1.5 minutes.

Calculate the number of scrapers which a pusher can serve. Determine the number of pushers to

serve 10 scrapers.

Solution Number of scrapers per pusher = =6/1.5 =4

Number of pushers for 10 scrapers = No. of scrapers o

10/4 =3

No. served by one pusher

9.4.3 Loader Shovel

This machine, also called as the front-end loader, can be used as earth

loader, earth transporter over short distances, and earth excavator in

loose soil. It can operate like a face shovel and bulldozer. It is available

with wheel mounting and track mounting.

The loader shovel can also be fitted with a benefactor attachment.

This benefactor type loader can be used for light excavation like

manholes, drain trenches, small pits, etc. and for loading of materials

into tippers. The ideal output data for loader shovel is given in Appendix 9.1.

The quantity of materials that can be hauled by the loader depends upon its bucket capacity. Loader

bucket capacities are specified by the manufacturer either in terms of heaped capacity or struck

capacity. However, planning can be based on the loose soil struck opacity of the bucket, and the

heaped capacity (loose soil) can be converted into struck capacity LOOSE* soil) as under

Bucket struck capacity • Bucket heaped capacity x Fill-factor where fill factor can b e taken as

Nature of soil Bucket fill factor 0.95, 0.95 0.80 0.70

Common earth, Sand and gravel, hard clay, blasted rock

9.4.4 Hauling Equipment

The type of earth hauling equipment primarily depends upon the haulage distance. A rough

Guideline for selecting equipment based on haulage distance is given in Table 9.3

Table 9.3

Guidelines for Selecting Equipment Based on Haulage Distance (in metres)

Type of Equipment Range of Haulage

Distance

1. Front-end loader track Up to 80

2. Front-end loader (wheeled) Up to 200

3. Bulldozers Up to 80

4. Towed scrapers 100-300

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5. Elevating self-loading

scrapers

100-1000

6. Single engine scrapers 500-1500

(dozer pusher arrangement)

7. Double engine motorised

scrapers

2000 and

above

(push pull arrangement)

8. Tippers and dump trucks 800 and

above

Mostly the excavated earth is hauled in heavy duty rubber-tired tippers, lorries, and rear-opening

dump trucks. Over long distances these vehicles vary in capacity from 5 m3 to 30 m3 dumpers.

Tipping lorries are employed for transporting materials over level grounds where as dumpers are

used for moving large quantities of materials across rough areas. Generally, front-end loaders and

excavators are used to load tippers and dumpers.

The number of haulage vehicles required can be calculated as under.

Haulage vehicle required = 1 + (Cycle time per trip of vehicle)

Load filling time of vehicle

example Construction of a military helipad at an altitude of 2400 m involves 80,000 m? (loose) of

area excavation in soft soil. This task is to be completed in 200 working hours. The company

entrusted with the execution of the task has two dozers each with an output of 220 no'/h under job

conditions. It also holds wheel loaders and 22 m dump trucks. One loader can load in trucks about

120 m3 of excavated soil per hour. The dump truck cycle time for disposal of excavated materials is

35 minutes. This includes 7 minutes of loading time by a loader team consisting of 2 loaders.

Estimate the output of front-end loader for loading excavated soil heap into dump trucks and

determine approximately the number of dozers, loaders and dumpers required to

complete the task on time.

Excavation quantity /Output/h x Working hour

80,000 / 220 x 200 S {8ay)

=Excavation/h by dozers / Loader output/h

=No. of dozers x dozer output/h / Loader output/h

_ 2 x 220 / 120

- 4 = 2 loader teams, each team consisting of 2 dozers.

(c) Dumpers required = 1 + / Loading time

For each loading team of 2 front end loaders

= 1+(35/7)=6

Total dumpers required = 2 x 6 = 12.

Dumper cycle time

Solution

(a) Dozers required =

(b) Loaders required =

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Types of Rollers Nature of Soil

100

% 100%

HOW THE TRANSPORTATION DISTANCE AFFECT THE SELECTION OF EARTH

HAULING EQUIPMENT?

The type of earth hauling equipment primarily depends upon the haulage distance. A rough

guideline for selecting equipment, based on haulage distance is given in Table below.

Hauling Distance of Equipment

S.No. Type of Equipment Range of Haulage Distance (in Meters)

1 Front-end loader track Up to 80 Meters

2 Front-end loader (wheeled) Up to 200 Meters

3 Bulldozers Up to 80 Meters

4 Towed scrapers 100~300 Meters

5 Elevating self-loading scrapers 100~1000 Meters

6 Single engine scrapers(dozer pusher

arrangement) 500~1500 Meters

7 Double engine scrapers(push pull

arrangement) 2000 Meters and above

8 Tippers and dump trucks 800 Meters and above

Haulage vehicle required = 1 + (Cycle time per trip of vehicle)

Load filling time of vehicle

9.5 EARTH COMPACTING AND GRADING

EQUIPMENT

The compacting process increases the density of soil by reducing

air void space. Consolidation, on the other hand, increases soil

density by reducing water voids. Consolidation is a long-term

process spread over years, whereas compaction can be achieved in

a few hours. Compaction improves bearing strength, permeability

and compressibility. Compacting equipment combine their static

weigh with tamping, vibration, impact and kneading action to

produce the desired compacting effort. Compaction equipment requirement

varies with soil characteristics and compacting effort. Exhibit 9.5 shows the type of compacting effort

and equipment required to compact different soils. The compacting equipment can be broadly

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classified into tamping foot rollers, pneumatic tired rollers, vibratory rollers, impactors, plate vibrators,

and smooth steel-wheel rollers.

9.5.1 Segmented Pods and Tamping Rollers

A tamping roller consists of one or more hollow steel cylindrical drums with rows of steel •tads like

sheep's feet mounted on it As the roller is towed with a crawler tractor, these studs punch into the soil

and compact it by tamping and kneading action. Generally, the compaction gets carried out to a depth

of 150 mm. The cylinder drum can also be filled with water or sand to add extra weight while

compacting.

9.5.2 Smooth Wheeled Rollers

These rollers have one or more smooth steel wheels, and the latest variety rollers are self-propelled.

The self-propelled tandem and 3-wheeled rollers are used for finishing compaction of layers up to 150

mm of sand, gravel and water bound macadam used in base courses. Smooth wheeled rollers are

employed for compacting bituminous materials specially the top layers in road surfacing operation.

Smooth wheeled rollers are classified either by type or weight or both. Various types of rollers include

3-wheel two axles, 2-wheel tandem and 3-wbeel tandem The weight of the rollers can also be

increased by ballasting with water, sand, or pig iron. Rollers are designated in terms of static weight

and ballasted weight, i.e. 15/20 tons means that the static weight of the roller is 15 tons and the

maximum weight when ballasted is 20 tons. In order to indicate the pressure exerted, these rollers

are also designated by specifying the minimum weight per linear width of roller, i.e. 60 kg/cm width.

9.5.3 Pneumatic Rollers

Pneumatic rollers are available in light, medium and heavy weights. They compact soil by a kneading

action. The weight of the equipment can be nearly doubled with ballasting using water, sand or pig

iron, and the ground pressure can be maintained as desired by controlling the weight of the ballast,

the number of the wheels, the width of the tyres and the tyre pressure. The pneumatic tired rollers are

rated in terms of tyre pressure (ground contact pressure) per unit area. It may be noted that the load

on the tyres determines the depth is which compaction is possible, where as both the tyre pressure

and the tyre load are important for achieving compaction near the surface. (See Table 9.4.)

9.5.4 Vibratory Rollers and Compactor*

Vibration improves compaction and save time when compared with the static weight method of

compaction. Vibrations set the rim roller in oscillation, and these in turn transmit vibrations to the soil.

Vibrations are induced by installing a rotating eccentric weight inside the roller drum. Vibratory rollers

combine the static weight with dynamic forces. Maximum compacting effort is produced when the

resonance frequency of the roller and soil coincide. Generally, the rating for the vibratory compactor

is stated as total applied force' expressed in tons and it is the numerical sum of the dynamic forces

plus static weight. The vibrating frequency is specified as cycles/minute. Vibration frequencies range

from 1400 to 3000 cycles per minute. Further, a slow displacement speed of say 2.5 to 4 km/h

produces a better effect than speedier movement.

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'Vibratory compactors are of various types and sizes. These include smooth drum vibratory rollers

and tamping foot vibratory rollers. These are widely used for compacting non-cohesive soils.

9.5.5 Production Output of Roller Compactors

The nature of soil dictates the type of compacting equipment required, and the dry density which can

be achieved. After the compacting equipment is selected, its average output can

be calculated as under:

Compaction in m3/hr = WSTEC / P

where W = Width compacted per pass (M) S - Compactor speed in M/h T = Thickness of

compacted layer in m3 E = Job efficiency factor C = Compacting factor P = Number of

passes required—varies from 4 to 6 and the approximate value of the compacting factor for the

changing state of soil. In the absence of actual data, the compacting factor

9.5.7 Graders

These are used to grade earthen road formations and

embankments to their finished shape within specified limits by

trimming the surface. The graders can also be used for forming

ditches, mixing and spreading soils, backfilling and scarifying

ground.

The motor grader is the equipment mostly used for grading and

finishing of large areas. Motor graders generally have engines

up to 300 HP and the latest models are provided with hydraulically controlled attachments. These

attachments include an excavation blade similar to the bulldozer, scarified, ripper and backhoe. The

blade of the motor grader has replaceable cutting edges. These blades come in flat, curved and

serrated styles. Motor graders are fitted with articulated frames for increasing maneuverability. Motor

graders are now available with automatic grade controls for achieving the desired grading. Grading

distance of 500 meters and above give optimum output. For shorter distances, task efficiency gets

reduced:

Distance in meters 50 100 200 500

Task efficiency 0.4 0.6 0.8 1.0

Graders' optimum output for finishing is measured in M?/hour on an area basis or km/hour

on an linear basis:

Output in m2 /hour = W.S.E / P

where,W = Width graded per pass S = Average speed in m/h E = Job efficiency factor P = Number of

passes (generally 4 to 6)

Example Calculate the time required to grade and finish 30 km of road formation with width equal to

thrice the width of the motor grader, using six passes of the motor grader with speed for each of the

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successive two passes as 6 km/h, 8 km/h and 10 km/h respectively. Assume machine efficiency

based on operator's skill, machine characteristics and working conditions as 75%

Average speed = 2x6 + 2x8x2x10 /6

= 8 km/h

Area to be graded per hour

_ Width graded per pass x Average speed x Machine efficiency / Number of passes

_ W x 8 x 1000 x 0.75 / 6 =

Numbers of hours required to grade and finish 30km long and 3W wide area

= total area / Area/hr

= (30x1000x3W) / (Wx8x1000x0.75) +6* *= (denominator) =90 hours.

9.5.8 Equipment selection criteria

Equipment selection criteria depends upon the following factors:

1. Compacting equipment – nature of materials, depth of fill, daily workload, and working

conditions

2. Grading Equipment – Nature of maeterials, daily workload, finished accuracy and working

conditions.

9.6 CONCRETING PLANT AND EQUIPMENT

Concrete is produced by combining basic materials like cement, aggregate and water into a

homogeneous, suitably designed, plastic mix that solidifies into structural and non-structural building

members. The process of production of concrete involves batching, mixing, transportation, placing,

consolidating and curing.

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9.6.1 Concrete Batching and Mixing Equipment

Batching is the process of proportioning cement, aggregates, water and admixture, by weight or

volume. Prior to mixing. The equipment used for batching and mixing can be divided into three

categories via mobile concrete mixers. Commonly called concrete mixers: centralized batching and

mixing plant : and mobile truck mixers which are covered under concrete transportation

9.6.2 Mobile concrete mixers

These mixer have a conical or circular rotating drum with baffle fitting inside. These are mounted on

pedestals with facilities for batching of various concreting materials. There are three types of

concrete mixers, viz. tilting drum mixers, non-tilting' drum mixers and reverse drum mixers. Tilting

drum mixers discharge the concrete by tilting the drum. Tilting mixers are used for producing very

small quantities of concrete or mortar mixes.

Non-tilting drums are suitable for requirements say up to 10 m3/b. These have a hopper fitted outlet

on the top for loading and another chute-fitted outlet on the bottom for discharge. The reverse-drum

mixers mix in one direction and discharge in the opposite direction.

The mobile concrete mixers vary in size from as slow as 100 liters to 400 liters or QW per cycle. The

size of the concrete mixers denotes the volume of concrete that can be mi^ in a single cycle, and

usually it is expressed in cubic feet or cubic meters, or the ratio©/ the concreting materials volume to

the wet concrete volume, for example 21/14 means a concrete mixer having maximum capacity to

hold dry concreting materials up to 21 cubic feet capable of producing wet concrete of 14 cubic feet.

Concrete mixers are available as static units and trailer-mounted towed units.

9,6.3 Central Batching Plant

A central batching plant includes all types of equipment and materials necessary to provide input to

the mixers and to deliver output to the concrete transporting system. Batching plants can be divide

into two categories, viz. medium size or low profile batching plants, and large volume or high profile

batching plants. Generally medium size batching plants have a rated capacity of 25 m3/h to 60 m3/ h

and are used for producing concrete for building construction projects where as batching plants

having higher capacity, say 120 m3/h, are employed for heavy construction or are used in the ready-

mix concrete supply business.

Experience dictates that for planning purposes, the average output of the central concrete batching

plants be taken as 60% to 70% of the hourly rated capacity for each working hour so as to cater for

various correction factors specially idle-time on account of non-utilization period and repairs.

9.6.4 Transportation Equipment

Equipment used for transportation of concrete, from mixer to placing site, depends upon

the distance involved and the volume of concrete to be placed. Wheelbarrows, with limited capacity

say 0.04 m3, and small motorized dumpers, with capacity up to 1.0 or1 are used for transporting and

placing small quantities of concrete.

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Concrete transit mixers are employed for transporting large quantities of concrete over long

distances. These mixers have a rotating drum mixer mounted on a truck. These transit mixers

transport wet concrete from the mixer to the placing site, and their rotating drums carrying capacity

varies from 3 m to 9 m concrete. Concrete specifications restrict the time from loading to discharge of

the concrete mixer as one hour without retarders, provided the drum is kept rotating to agitate the wet

mix. For long distances, say exceeding two hour's travel time, the dry mix can be transported in

specially designed truck-mixers, and the concrete is manufactured at the placing site by mixing these

materials with water.

The number of truck-mixers required for transporting concrete can be worked out by evaluating the

cycle-time. Consider a typical mixer cycle-time data of 6 m3 truck-mixer, given below:

Loading time for 6 m3 truck-mixer = 14 minutes

Travel time of loaded truck-mixer to site = 7.5 „

Average waiting time at site = 7.5 „

Discharge time at site using concrete pump = 15 „

Travel time for return trip = 5 „

Total cycle time = 49 minutes

Therefore truck-mixers required for continuous supply

Cycle time , . (cycle time \ DISCHARGE ) + 1 (spare) =49/50 +1 = 5 No‘s

□ 9.7 CRANES FOR MATERIAL HOISTING

Cranes are predominantly used for handling including lifting, lowering and swing shifting of small to

heavy loads. Cranes come in many types such as crawler-mounted mobile

cranes, self-propelled rubber-tired wheels, telescopic jib cranes, truck-mounted strut-jib

cranes and tower cranes. The commonly used cranes are shown in Exhibit 9.8.

9.7.1 Mobile Cranes

In wide spread project sites, mobile cranes provide the best means for lifting and shifting

of small to heavy loads. These cranes can move over level firm surfaces as well as on rough terrains.

Mobile cranes are of the following types:

1. Crawler-mounted cranes These cranes spread their dead load over larger area through their

long tracks, and as such are useful while working in unprepared surfaces. The boom of these

cranes comes in sections which are joined by pin connections. The straight boom thus formed

can lift loads over a radius of 30 to 40 metres. In order to overcome the ground obstruction to

the inclined boom, a fly-jib (say, 18 meters in length) is attached to the top of the end boom

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2. Self-propelled rubber-tired wheels cranes These cranes have greater mobility

over hard surfaces and are in great demand for shifting and transporting light loads over short

distances, and for off-loading of medium to heavy loads. Self-propelled

cranes can be broadly divided into three categories:

(a) Strut-jib cranes for shifting small loads at a distance, where ground obstruction

restricts the utility of the crane.

(b) Cantilever-jib crane provides greater clearance under the jib for heavy and bulky

loads.

(d) Telescopic-jib crane provides flexibility in adjusting distances and heights of lifts.

It has greater mobility on roads than other self-propelled cranes.

9.7.2 Estimating Crane Output

The crane's capacity to handle loads from one location to another is given by:

Crane output/Hour = Load/cycle x cycles/hour.

Calculation of the output and cycle time depends upon many variables, and it can best be determined

by referring to machinery manuals and site trials.

It is important that manufacturers' manuals must be referred to in order to determine the tipping

load at a given radius and the safe working load of the crane. Generally the safe working load varies

from 67 to 75% of the theoretical crane tipping load.

For initial planning purposes, the cycle time can be computed as outlined below. However, the data

indicated is for illustration purposes only:

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Estimating Crane Output The crane's capacity to handle loads from one location to another is given by:

CRANE CAPACITY: Crane output/hour = Load/cycle × cycles/hour

Calculation of the output and cycle time depends upon many variables and it can, at best, be

determined by referring to machinery manuals and site trials.

It is important that manufacturers manuals must be referred to in order to determine the tipping load

at a given radius and the safe working load of the crane. Generally, the safe working load varies

from 67 to 75% of the theoretical crane tipping load.

For initial planning purposes, the cycle time can be computed as outlined in Table However, the

data indicated is for illustration purposes only.

Crane Cycle Time Computation

S. No. Activity (medium-sized crane) Time in

minutes

1. Hooking load at ground level 1.0 minute

2. Raising load from ground level to a height of 30 meters at 60 metres/minute 0.5 minute

3. Slewing through 120 degrees at 60 degree/minute 0.5 minute

4. Travelling on rails for 45 meters at 30 metres per minute 1.5 minute

5. Moving trolley at jib level for unloading and positioning by 15 metres at 15

metres per minute 1.0 minute

6. Unhooking load 1.0 minute

7. Lowering load by 5 metres at 60 to 100 meters/minute, and resting at the

proper place 1.0 minute

8. Raising hook by 5 meters (overlapping) 0.0 minute

9. Slewing to original loading position 1.0 minute

10. Moving trolley at jib level to loading position 0.5 minute

11. Travelling on rails to original loading position 1.5 minutes

12. Lowering hook 0.5 minute

Total cycle time after disregarding effect of small overlapping activities 11.0 minutes

Therefore, the above crane, operating with a job efficiency of 44 mins/hr and shifting a 5 ton load in

each cycle, shall handle 5 ton load × cycles in one hour (of 44 minutes).

= 5 × 44 min / 11 min

= 20 tons/hr

It may be noted that the rated crane capacity is equal to the maximum load-lifting capacity at the

minimum operating radius.

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10.2 COST CONSIDERATIONS

The economic use of equipment is related to its employment cost. Hourly plant employment cost

forms the basis for the cost estimation of work executed by the plant. The plant employment cost can

be determined by computing plant owning and operating costs as follows:

Equipment employment cost = Owning cost + Operating cost.

There are many factors, determinate as well as indeterminate, which affect the plant owning and

operating costs. Some of these factors include the state of the plant (old or new) and its capitalized

cost, the source through which the capital is to be raised in case of a new purchase, the site delivered

price, the implication on corporate taxes for the new purchase, the company's policy regarding

capitalization, the economical plant life in years, the resale value after a useful life, the number of

hours of operational employment contemplated in a year, the past performance records in the case of

an old plant, the job conditions, the skill of the operator, and the repair and maintenance facilities

including timely supply of spares. The main factors affecting the owning and operating costs are

explained below. These are followed by a simplified approach with examples for estimating these

costs. There is no substitute for experience while evaluating the plant employment costs. Therefore,

the method of estimation of the hourly plant cost given in succeeding paragraphs should be taken as

simplified guidelines to be modified by the experienced estimator according to the situation

10.2.1 Equipment Owning Costs

It represents the cost of ownership of the equipment. These costs are incurred by the

owner whether the equipment Is used or not. The equipment owning costs include:

(a) Depreciation cost.

(b) Cost of capital invested.

(c) Taxes and insurance.

Depreciation cost Depreciation is the loss in market value of the plant over a period of time,

resulting from usage, wear and tear or age. There are several methods of calculating the annual

depreciation that should be charged to the project to cover the plant capital cost. These include the

straight line method, sinking fund method, declining fund method, sum of digit method and experience

of owning and operating a similar plant. Exhibit 10J2 outlines various methods of determining

depreciation. Depending upon the company policy, market trends and nature of usage, an

appropriate method of depreciation can be adopted.

The straight line method is most commonly used for depreciation estimation. The information

required is the delivered- at -site purchase cost including attachments, the residual or resale value

after use, and the equipment's usage life period. The tyre replacement cost is not included in the

depreciation estimation as it is dealt under operation costs.

Annual depreciation = Delivered price – Residual value

ownership period In year

Depreciation per usage hour = Annual Depression

Usage hours per year

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Consider an example of a crawler tractor. Its purchase price is $100,000 and the assessed resale

value after using for 5 years is 25% of the delivered price. This equipment is planned to operate 2000

hours per year.

Delivered price = $100,000.

Residual value = 25% of $100,000 = = $25,000.

Annual depreciation = $ 100000-25000 / 5 = $ 15000.

Investment costs The costs cover interest on the money invested in equipment/plant, taxes of all

types, insurances, licenses and storage expenses. Rates for these costs vary with owners and

locations. However, these can be estimated based on the prevailing rates at the project location.

Hourly Investment = Average investment x Annual interest rate

Annual usage hours

= (N+1) Delivered price x I

2N x Annual usage hours

where,

N = Ownership years t,,,,,,, I= Rate of interest.

10.2.2 Equipment Operating Costs

The cost of operating the equipment/plant includes fuel costs, routine maintenance costs, major

repair costs, operators' costs, tyre replacement costs, and overhead costs.

Fuel costs Most of the construction plants at project sites use combustion ignition engines as the

prime mover. These engines require fuel. The requirement of fuel at full load can be approximately

estimated from the engine fly wheel horsepower CHP rating.

Cost of fuel consumed in one hour = Cost per litre x Hourly fuel consumption.

Hourly fuel consumption = Hourly fuel consumption at full load x Operating factor.

The fuel price per litre, delivered at the site, is obtained from the local suppliers as it varies from

place to place. The rate of consumption depends upon the type of engine (diesel or petrol), the state

of the engine and the working conditions.

1. Petrol engine fuel consumption per hour * =0 .22 liters x rated HP x load factor

2. Diesel engine fuel consumption per hour *= 0 .15 liters x rated HP x load factor

Routine maintenance costs Maintenance costs include the cost of lubricating oil, grease, filter,

batteries, minor repairs, and the labour involved in performing maintenance. The quantity of

lubricating oil required for lubrication can be calculated from the manufacturer s manual showing

the number of hours after which the oil changing is needed. Depending upon the operating

conditions, the oil changing generally varies from 50 to 200 engine running hours. Generally, the

maintenance costs including service, labour (mechanic) and minor repairs vary with the type of

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equipment involved and the project environment and these can be approximately calculated as

proportion of hourly fuel coat as follows. '

Operating conditions Hourly maintenance cost

Favorable 1/4 Fuel cost

Average 1/3 Fuel cost

Unfavorable 1/2 Fuel cost

Major repair costs These costs vary with the type of equipment, the condition of the plant, the prices

of spare parts, the maintenance charges and the operating conditions, Generally, the cost of repairs

including cost of spare parts and labour can be roughly taken as equal to the depreciation cost x

repair factors. For special purpose equipment such as the rock-crushing plant, the wear and tear is

more and needs detailed estimation. Similarly, for electrically operated plants such as the concrete

weight-batching and mixing plant, the repair cost is less than the depreciation cost.

Repair cost = Depreciation cost x Repair factor.

Repair costs vary appreciably, with the age of the equipment. The repair cost in the first year of

acquiring the new equipment is far less than say in the fifth year of its operation. An approximate

year-wise repair cost can be estimated using the following relationship:

- . . . ,

Repair cost during nth year = n x Value to be depreciated

Digit sum of equipments file in years

for example, if the total value of depreciation of wheeled equipment (repair factor -0.76) works out

as $75,000 and its life is 5 years; then the repair cost during each year of operation (working 2000

hours per year) can be estimated as under:

Total repair cost = Total depreciation x Repair factor = $75,000 x 0.75 =

$56,250.

Tyre costs for wheeled equipment It is not easy to forecast the tyre life due to a large

number of interacting variables. In fact there is no accurate method of determining tyre life. The tyre

manufactures provide indication of tyre life but these should be taken as guidelines only. The tyre life

should be assessed by experienced plant engineers, m the absence of such a facility, Table 10.5

following can be used to estimate tyre life

Hourly tyre replacement cost = 1.15 x tyre price x no of tyres

Tyre life in hours

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10.2.3 Method of Estimation of Owning and Operating Costs

Hourly owning and operating cost of an equipment can be calculated, moving step listed:

The step-by-step approach followed is self explanatory.

Exhibit 10.3

Construction Equipment Costing Hourly Owning And Operating Cost Estimate

Ownership Data

Machine Nomenclature Crawler Tractor

A. Rated horsepower 250

B. Ownership period (years) 5

C. Estimated Usage (Hours/years) 2000

D. Ownership Usage (Total Hours) 10,000

(Confifa'on-SeveiB/Average/Moderate) Severe

Owning Costs

E. Delivered Price 100,000

F. Tyres Original Cost Nil

G. Delivered price less tyres (E-F) 100,000

H. Residual Value at Replacement 25% 25'000

(Expressed as % of G)

I. Value to be Depreciated (G-H) ___ 75000

J. Depreciation per hour (I/D) 7.5

K. Interest Cost per hour (B+1)xE x rate 4.8 rate- 16%

2Bx D

L. Taxes & Insurance per hour (B+1)xE x rate 1.2 rate- 10

2Bx D

M. Owning Cost per hour (J + K + L) 13.5

Operating Costs

N. Pole (Consumption diesel = 0.227 liters x4.50 2.25

O. Oil, Lubricant, Filters etc. OV x Service factor) Nil

P. Tyre Replacement Cost (= F/tyre life) 712

Q. Repairs <J x Repair Factor) Nil

R. Special Wears 13.87

S. Total Operating Cost per hour (Sum of N to R)

T. Total Owning sad Operating Cost (M+ s) 27.37

Manpower Costs „

U. Operator Costs per hour 10

V. Helpers Cosu per hour nil

W. Total Crew Cost per hour ______

Total Owning & Operating Cost (7* + W0 37.37

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10.5 SUMMARY OF EQUIPMENT SELECTION CONSIDERATIONS Selection of an equipment or plant system to perform an assigned task depends upon many

interrelated factors. These factors, mostly covered in Chapters 9 and 10, are outlined below:

10.5.1 Task Considerations

Nature of task and specifications.

Daily or hourly forecast of planned production.

Quantity of work and time allowed for completion.

Distribution of work at site.

Interference expected and interdependence with other operations.

10.5.2 Site Constraints

Accessibility to location.

Maneuverability at site.

Working space restrictions.

Altitude and weather conditions.

Working season and working hours.

Availability of local resources of manpower, materials and equipment.

Availability of land, power supply and water supply for workshop and camp.

Availability of equipment hiring, repair and maintenance faculties, locally.

Availability of fuel, oil and lubricants.

10.5.3 Equipment Suitability

Type of equipment considered suitable for the task.

Make models and sizes of special purpose, and general purpose equipment that can handle the task.

Production capability, serviceability condition and delivery time of each equipment t

Equipment already owned by the contractor.

Usefulness of the suitable equipment available for other and future tasks

10.5.4 Operating Reliability

Manufacturer's reputation.

Equipment components, engine-transmission, brakes, steering .operator's cabin

Use of standard components.

Warranties and guarantees.

Vendor's after-sale service.

Operator's acceptability, adaptability and training requirements.

Structural design.

Preventive maintenance programme.

Safety features.

Availability of fuel, oil and lubricants.

10.5.5 Maintainability

Ease of repair and maintenance.

Vendor's after-sale service, repairs, spares and maintenance.

Availability of spare parts.

Standardization consideration.

10.5.6 Economic considerations

Owning costs.

Operating costs.

Re-sale or residual value after use.

Replacement costs of existing equipment.

10.5.7 Commercial Considerations

Buy second-hand or new equipment.

Rent equipment.

Hire-purchase equipment.

Purchase or lease.

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Concreting ► Concrete is a construction material composed of cement (commonly Portland cement) as well

as other cementitious materials such as fly ash and slag cement, aggregate (generally a

coarse aggregate such as gravel, limestone, or granite, plus a fine aggregate such as sand),

water, and chemical admixtures.

Major concreting equipment

1. Mixing equipment

Portable concrete mixer

Batching plants

2. Transporting equipment

Transit mixers

Concrete dumpers

3. Delivery equipment

Concrete pumps

Hoist and buckets

4. Compacting equipment

Needle vibrators

Surface vibrators

Concreting plant and equipment

The process of production of concrete involves batching, mixing, transportation and

pumping of concrete

Batching is the process of proportioning cement, aggregates water and admixture by

weight or volume prior to mixing

The equipment used for batching and mixing can be divided into three categories

1. Mobile concrete mixers

2. Centralized batching and mixing plant

3. Mobile truck mixers

1. Mobile concrete mixers

These mixers have a conical rotating drum with baffle fittings inside

These are mounted on pedestals with facilities for batching of various concreting materials

There are 3 types of concrete mixers

Tilting drum mixers

Non tilting drum mixers

Reverse drum mixers\

Tilting drum mixers discharge the concrete by tilting the drum which is used for

producing very small quantities of concrete

Non tilting drums are suitable for requirements say up to 10cum/hr.These have a hopper

fitted outlet on the top for loading and another chute fitted outlet on the bottom of

discharge

The reverse drum mixers mix in one direction and discharges in other directions

The mobile concrete mixers will vary in size from 100 liters to 400 liters per cycle

The size of the concrete mixers denotes the volume of concrete that can be mixed in a

single cycle and usually it is expressed in cum or the ratio of the concreting materials

volume to the wet concrete volume.

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The hourly output of a concrete mixer can be calculated by multiplying production in cum

per batch into the number of batches per hour.

2.Central batching plant

A central batching plant includes all types of equipment and materials necessary to provide

input to the mixers and to deliver output to the concrete transporting system.

Batching plants are divided into 2 categories medium sized or low profile batching plant and

large volume or high profile batching plant.

Medium sized batching plant have a rated capacity of 25cum/hr to 60cum/hr and used for

producing building construction projects where as batching plant having higher capacity say

120cum/hr are employed for ready mix concrete business.

For planning purpose the average output of the central concrete batching plants be taken as

60 to 70% of the hourly rated capacity so as to cater for various correction factors specially idle

time on account of non utilization period and repairs.

Transporting equipment

► Equipment used for transportation of concrete from mixer to placing site depends upon the

distance involved and the volume of concrete to be placed.

► Wheel barrows with limited capacity 0.04cum and small motorized dumpers with capacity up to

1 cum are used for transporting small quantities of concrete

Transit mixers

Concrete transit mixers are employed for transporting large quantities of concrete over long

distances.

These mixers have a rotating drum mixer mounted on a truck.

These transit mixers transport wet concrete from the mixer to the placing site and their rotating

drum carrying capacity varies from 3cum to 9cum of concrete.

Concrete specifications restrict the time from loading to discharge of concrete as one hour

without retarders provided the drum is kept rotating to agitate the wet mix.

For long distances say exceeding 2 hrs travel time the dry mix can be transported in specially

designed truck mixers and the concrete is manufactured at the placing site by mixing these

materials with water.

The number of truck mixers required for transporting concrete can be worked out by evaluating

the cycle time.

Concrete transport truck

Special concrete transport trucks (in–transit mixers) are made to transport and mix concrete

from a factory/plant to the construction yard.

They are charged with dry materials and water, with the mixing occurring during transport.

(Although, more modern plants load the truck with 'Ready Mixed' concrete.

With this process, the material has already been mixed, and then is loaded into the truck. The

ready mix truck maintains the material's liquid state, through agitation, or turning of the drum,

until delivery.)

The interior of the drum on a concrete truck is fitted with a spiral blade. In one rotational

direction, the concrete is pushed deeper into the drum.

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This is the direction the drum is rotated while the concrete is being transported to the building

site.

This is known as "charging" the mixer. When the drum rotates in the other direction, forces the

concrete out of the drum.

From there it may go onto channels to guide the viscous concrete directly to the job site.

If the truck cannot get close enough to the site to use the channels, the concrete may be

discharged into a concrete pump connected to a flexible hose, or onto a conveyor belt which

can be extended some distance (typically ten meters).

A pump provides the means to move the material to precise locations, multi-floor buildings,

and other distance prohibitive locations.

Rear discharge" trucks require both a driver and a "man" to guide the truck and chute back and

forth to place concrete in the manner suitable to the contractor.

Newer "front discharge" trucks have controls inside the cab of the truck to allow the driver to

move the chute in all directions.

Concrete mixers generally do not travel far from their plant, as many contractors require that

the concrete be in place within 90 minutes after loading.

If the truck breaks down or for some other reason the concrete hardens in the truck, workers

need to enter the barrel with jackhammers; dynamite is still occasionally used to break up

hardened concrete in the barrel under certain circumstances.

Six-axle Advance Ready Mix truck

Volumetric Concrete Mixer

Front discharge truck

A rear–discharge concrete transport truck

Off road mixer truck

Ready mixed concrete

Ready mixed concrete can be ordered in several ways

Recipe batch – The purchaser specifies the responsibility for the proportioning of the concrete

mixture

Performance batch - The purchaser specifies the requirements for the strength of concrete.

Part performance and part recipe – The purchaser specifies minimum cement the required

admixtures, and the strength requirements, allowing the producer to proportion the concrete

mixture within the constraints.

Ready mixed concrete is supplied to sites in specially designed truck mixes which is basically a

mobile mixing drum mounted on a lorry chasis.

Truck mixes can be employed in one of three ways

1. Loaded at the depot with dry batched materials plus the correct quantity of water, the truck

mixer is used to complete the mixing process in the depot before leaving the site. During

transportation the mix is kept agitated by the revolving drum.

2. Fully or partially mixed concrete is loaded into the truck mixer at the depot. During

transportation the mix is agitated by the drum revolving in 1 to 2 revolutions per minute. On

arrival the mix is finally mixed by increasing the drum revolution to between 10 and 15

revolutions per minute.

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3. When the time taken to deliver the mix to the site may be unacceptable the mixing can take

place on the site by loading the truck mixer at the depot with dry batched materials and adding

the water upon arrival on site.

To obtain maximum advantage from the facilities ,the supply instruction should contain the

following

Type of cement

Types and minimum size of aggregates

Test and strength requirements

Testing methods

Slump or workability requirements

Volume of each separate mix specified

Delivery programme

Placing of concrete

Once the concrete arrive at the site ,it must be moved to its final position without segregation and

before it has achieved its initial set

Methods include

Buckets

Motor propelled buggies

Chutes

Belt conveyers

Concrete pumps

Concrete bucket

Conveyer belt

Pumping concrete

Concrete Batch Mixing Plant with

Transit Mixer

Concrete Batch Mixing Plant:

Weigh Batcher

C.C. Mixer

Handling & Transporting Equipment:

Bucket Handled By Crane

Concrete Pump

Lift Dumper

Ker Laying Machine

Concrete Paver

Canal Laying Pavers:

Pin / Poker Vibrator

Surface / Plate Vibrator

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Buckets

Permit concrete placement at the lowest practical slump

Gates should be designed so that they can be opened and closed at any time during the

discharge of concrete.

Segregation must be avoided

Buggies

Hand buggies and wheel barrows are capable of carrying 4 to 9 cft of concrete.

Recommended for distance less than 200ft

Channels

Transfer concrete from a higher elevation to a lower elevation

They should have a round bottom and the slope should be steep enough for the concrete to flow

continously.

Belt conveyers

1.Portable or self containers

2.Feeders or series conveyers

Side discharge or spreader conveyer

All types must have proper belt size and speed to achieve the desired rate of transportation

Concrete pumps

The pump must be fed with concrete of uniform workability and consistency

Pumps can be mounted on trucks and trailers.

The truck mounted pump and boom combination is efficient and cost effective

The following rules must be followed

1. Min pipe dia 5 inch

2. Always lubricate the line with cement paste

3. Ensure a steady uniform supply of concrete

4. Always presoak the aggregates before mixing

5. Avoid the use of reducers in the conduit line

6. Never use aluminum lines. Aluminum and Portland cement react ,librating hydrogen gas that

can cause rupture of concrete

Generally small diameter pipes of 75 and 100mm are used for vertical pumping whereas large

diameter up to 150mm are used for horizontal pumping

The time required on site to set up a pump is approximately 30 to 45 min.

The output of the concrete pump will be affected by the distance the concrete is to be

pumped.

Therefore the pump should be positioned so that it is too close to the discharge point as it is

practicable.

Pours should be planned so that they progress backwards towards the pump removing the

redundant pipe lengths as the work proceeds.

As compared to the conventional placing of concrete where the output is 15 to

20cum/hr.These typical output of the pumps are 60 to 100cum/hr but certain amount of skill

and experience is required

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Advantage of using concrete pumps is

Concrete is transported from point of supply to placing position in one continuous operation

Faster pours can be achieved with less labour

No segregation of mix is experienced with pumping and a more consistent placing and

compaction is obtained requiring less vibration

Only method available for conveying wet concrete both vertically and horizontally in one

operation

Net cost of placing concrete is reduced

Limitations of the concrete pumps

Concrete supply must be consistent and regular which can be achieved by well planned and

organized deliveries

Under ideal conditions the discharge rate of each truck mixer can be 10minutes

Concrete mix must be properly designed and controlled since not all concrete mixes are

pump able.

The concrete is pumped under high pressure which can cause bleeding and segregation of

the mix.

Therefore the mix must be properly designed to avoid these problems as well as having

good cohesive, plasticity and self lubricating properties to enable it to pump through the

system without excessive pressure and blockages.

Consolidating and Finishing

1. Consolidation aims at removing air voids in the concrete at the time of placing and it is

achieved with the help of concrete vibrators

2. Finishing operations make use of screed vibrators and tools necessary for undertaking

various types of finishes.

Cement storage

Cement can be supplied in 50 kg bags for storage on site.

If large quantities of cement are required an alternative method of storage is the silo which

will hold cement supplied in bulk ideal conditions.

A typical cement silo consists of an elevated welded steel cylindrical container supported on

four crossed braced legs with the bottom discharge outlet to the container.

Storage capacities range from 12b to 50 tons. Some of the advantages are

Cost of bulk cement is cheaper per ton than baggage cement

Unloading is by direct pumping from delivery vehicle to silo

Less site space is required for any given quantity to be stored on site

First cement delivered in the site to be used since it is pumped into the top of the silo and

extracted from the bottom.

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Crusher

Crusher is a machine designed to reduce large solid material objects into a smaller volume,

or smaller pieces.

Crushers may be used to reduce the size, or change the form, of waste materials so they

can be more easily disposed of or recycled, or to reduce the size of a solid mix of raw

materials so that pieces of different composition can be differentiated.

Crushing is the process of transferring a force, through a material made of molecules that

bond together more strongly, and resist deformation more, than those in the material being

crushed do.

Crushing devices hold material between two parallel solid surfaces, and apply sufficient force

to bring the surfaces together to generate enough energy within the material being crushed

so that its molecules separate from (fracturing), or change alignment in relation to

(deformation), each other.

The earliest crushers were hand-held stones, where the weight of the stone provided a boost

to muscle power, used against a stone anvil.

Production of crushed stone aggregates involves 1.Quarry operations 2.Reduction operations.

The quarry operations are

1. Drilling

2. Blasting

3. Loading

4. Transporting

The reduction operations are

1. Crushing

2. Screening

3. Handling

4. Storing

Proper coordination between quarry operation and crushing operations should be employed

Description

In industry, a crusher is typically a machine which uses a metal surface to break or compress

materials.

Mining operations use crushers, commonly classified by the degree to which they fragment the

starting material, with primary and secondary crushers handling course materials, and tertiary

and quaternary crushers reducing ore particles to finer gradations.

Typically, crushing stages are followed by milling stages if the materials need to be further

reduced.

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Crushers are used to reduce particle size enough so that the material can be processed into

finer particles in a grinder.

Layout of crusher

Crushers may be classified by stage of crushing.

1. Primary crusher –Which receive the stone directly from the quarry and produces first reduction

in size.

2. Secondary crusher – Output of primary crusher is fed to a secondary crusher which further

reduces the size.

3. Tertiary and others –Some stones may pass through third or fourth crusher

The commonly used crushers are

1. Primary crusher –Jaw crusher and Gyratory crusher

2. Secondary crusher –Cone crusher and Roll crusher

3. Tertiary crusher – Rod mill and Ball mill

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If it is a single process, excessive fines will be generated and normally there is a limited market

for fines.

As stone passes through the crusher, the reduction in size can be expressed as the reduction

ratio, i.e. the ratio of the crusher feed size to the product size.

Crushing equipment selection

The kind of stone to be crushed

The required capacity of the plant

The maximum size of the feed stones

The method of feeding the crusher

The required size ranges of the product

By compaction method

Jaw crusher

A jaw or toggle crusher consists of a set of vertical jaws, one jaw being fixed and the other

being moved back and forth.

The jaws are farther apart at the top than at the bottom, forming a tapered chute so that the

material is crushed progressively smaller and smaller as it travels downward until it is small

enough to escape from the bottom opening.

The movement of the jaw can be quite small, since complete crushing is not performed in

one stroke.

The inertia required to crush the material is provided by a weighted flywheel that moves a

shaft creating an eccentric motion that causes the closing of the gap.

Machines operate by allowing stone to flow into the space between the two jaws, one is

stationary while the other is movable.

The movable jaw is capable of exerting a pressure sufficiently high to crush the hardest rock.

Jaw crushers are designed with the toggle as the weakest part.

This toggle will break if the machine encounters an uncrushable object.

Single and double toggle jaw crushers are constructed of heavy duty fabricated plate frames

with reinforcing ribs throughout.

The crusher‘s components are of high strength

design to accept high power draw.

Manganese steel is used for both fixed and

movable jaw faces. Heavy flywheels allow

crushing peaks on tough materials

Double Toggle jaw crushers may feature hydraulic

toggle adjusting mechanisms.

Single toggle

When the eccentric shaft of the single toggle crusher

is rotated, it gives the movable jaw both a vertical and horizontal motion

This type is used in portable rock crushing plants because of its compact size and lighter weight

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Double Toggle

The Blake type is a double –toggle jaw crusher

The movable jaw is suspended from the shaft

Rotating an eccentric shaft actuates the two toggles

and these produce the crushing action.

Size of Jaw and Roll crusher product

The figure below represents the percent of

material passing or retained on screens having

the size openings indicated.

To read the chart selects the vertical line

corresponding to the crusher setting.

Then move down this line to the number that indicates the size of the screen opening.

From the size of the screen opening proceed horizontally to the left to determine the percent

of material passing through the screen or to the right to determine the percent of material

retained on the screen.

Q .1 A jaw crusher with a closed setting of 3 inches is fed at the rate of 50 tons/hr. Determine

the amount of stone produced in tons per hour within the following size ranges; in excess of 2

inch, between 2 and 1 inch, between 1 and ¼ inch, and less than ¼ inch.

The amount retained on a 2 inch screen is 42% of 50, which is 21 tons per hr. The amount in each

of the size ranges is determined as

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Size

range(in)

Percent passing

screens

Percent in size

range

Total output of

crusher

(tph)

Amount produced in size

range (tph)

Over 2 100-58 42 50 21.0

2 - 1 58-33 25 50 12.5

1 – ¼ 33-11 22 50 11.0

¼ - 0 11- 0 11 50 5.5

Total 100% 50.0

Gyratory crusher

A gyratory crusher is similar in basic concept to a jaw

crusher, consisting of a concave surface and a conical

head; both surfaces are typically lined with manganese

steel surfaces.

The inner cone has a slight circular movement, but does not

rotate; the movement is generated by an eccentric

arrangement.

As with the jaw crusher, material travels downward between

the two surfaces being progressively crushed until it is small

enough to fall out through the gap between the two

surfaces.

A Gyratory Crusher is one of the main types of primary crushers in a mine or ore processing

plant. Gyratory crushers are designated in size by the size of the receiving opening.

Gyratory crushers can be used for primary or secondary crushing. The crushing action is caused

by the closing of the gap between the mantle line (movable) mounted on the central vertical

spindle and the concave liners (fixed) mounted on the main

frame of the crusher.

The gap is opened and closed by an eccentric on the

bottom of the spindle that causes the central vertical spindle

to gyrate. The vertical spindle is free to rotate around its

own axis.

Impact crushers

Impact crushers involve the use of impact rather than

pressure to crush material.

The material is contained within a cage, with openings

on the bottom, end, or side of the desired size to allow

pulverized material to escape.

This type of crusher is usually used with soft and non-

abrasive material such as coal, seeds, limestone, gypsum or soft metallic ores.

The stones are broken the by application of high speed impact forces.

Speed of rotation is important to the effective operations of these crushers as the energy

available for impact varies as the square of rotational speed

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Cone crusher

Used as secondary crusher

Capable of producing large quantities of

uniformly fine crushed stone

The conical head on the stone crusher is usually

made of manganese steel

The maximum diameter of the crusher head can

be used to designate the size of the cone

crusher.

A cone cutter differs from a gyratory crusher in these

aspects

It has a shorter cone

It has a smaller receiving opening

It rotates at a higher speed

It produces a more uniformly sized stone

Reduction ratio of the major type of crushers

Roll crusher

Used for producing additional reductions in the size

A roll crusher consists of heavy cast iron frame equipped

with either one or more hard steel rolls each mounted on a

separate horizontal shaft.

Feed size

The maximum size of the material that fed to a roll crusher is

directly proportional to the diameter of the rolls.

The maximum size particles that can be crushed are determined as follows

A = 0.085 R +C

A is the maximum size feed

R is the radius of the rolls

C is the roll setting or the size of the finished product

Capacity of the roll crusher

The capacity of the roll crusher will vary with the

type of stone

size of feed

size of the finished product

width of the roll and the speed at which the roll rotate.

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Capacity of the roll crusher in tonnes/hr =

CW¶RN

864

Q is the probable capacity in tons per hour

C is the distance between rolls in inches

R is the radius of the roll in inches

N is the speed of the roll in rpm

W is the width of the roll in inches.

Advantages

It produces more per hour of material of specified size considering weight of crusher.

It can handle any material for hardest to softest.

It is cheaper in initial cost and in installation.

Less operation and maintenance.

It consumes less power.

It produces uniform material

Uniform wearing of the surface.

Hammer mills It is the most widely used impact crusher which can be used for primary as well as

secondary crusher

As the stone to be crushed is fed into the mill the hammers which revolve at high rpm strike

the particles breaking them and driving them against the breaker plates which further reduce

their sizes.

Special aggregate processing units

Rod mill and ball mill To produce fine aggregate such as sand from stones that are crushed to suitable sizes rod or

ball mills are frequently used.

The rod mill is charged with steel rods and as the mill rotates slowly the stone is constantly

subjected to the impact of the tumbling rods.

In a ball mill steel balls are used for grinding.

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MECHANIZATION OF CONSTRUCTION INDUSTRY By Prof. K.R.Ramana

BACKGROUND

The invention of wheel in the year about 3000 BC was the beginning of the era of civilization. Men

were contended at that time with slow movement of men and material. Science and Technology has

now advanced considerably hence there is need to execute jobs with speed, complying with the

Project specifications of the client companies, within the estimated cost. With the invention of Steam

Engine in 1780 by James Watt and Diesel Engine by Rudolph Diesel in 1910 there was breakthrough

in technology and the substitution of power by Machines from Human efforts became profound.

The evolution of construction plant and equipment is another product of the attempts of man to be

master of his environment and to shape it to his maximum benefit. Thus Mechanized development in

Industry, Communication, Agriculture and Construction has inevitably meant the advances of

Economic growth.

India had only a few Construction and Mining equipment during the Pre-independence period. The

oldest place of equipment findings origin in 1913 is the Steam Power driven equipment, i.e. the crane.

In the post independence period, native skill soon developed to a degree of specialization in various

fields to augment the development resources. The value of the Equipment added in the Five year plan

from 1956 to 1970 as reported in Plant and Machineries committee report of 1972 was 26,600 lakhs

CONSTRUCTION INDUSTRY TODAY

Today construction activity serves to catalyze the economic growth of the country. A vibrant

construction industry is essential in a developing economy like India to meet the needs of deficient

infrastructure facilities. Moreover, investments in construction have a positive domino effect on supplier

Industries, thereby kick starting economic development.

The construction Industry in India is valued at Rs 2.40,000 cores and is galloping ahead at a rate of 7

to 8 % per annum. Over the next 10 years, the government has planned investments in the

infrastructure sector, roads, water supply and irrigation, housing, ports, energy, telecommunications

etc., to the tune of Rs 20,00,000 crore. Of this total amount nearly 40 to 50% would be spent on

construction activities.

CONSTRUCTION EQUIPMENT MARKET

The Indian construction equipment market is roughly around Rs 10,000 crore per annum. It

comprises of domestic production as well as imported equipments. The construction equipment

market is growing at a pace of about 20% per annum. Some of the leading Multinational

construction equipment manufacturers have established operations in India to take advantage

of the burgeoning market opportunities. Companies that had their presence in the Market

include Fiat Allis (Italy), Samsung (south Korea), Belas and Uralmash (Russia), Liebher

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(France), Caterpillar, Terec, Unit Rig, Ingersoll Rand, WABCO & Bucyrus Eric (USA), O & K

(Germany), P & H ( a US & Japnese combine), Komatsu (Japan). South Korean companies

landed price of construction equipment are competitive compared with local equipment. The

stocks of equipment with all agencies dealing with imported equipment is around 3500 crore

which is expected to go upto Rs 11000 crore in the next decade. India‘s construction

equipment manufacturing market should become much more competitive. Price and on time

delivery of products will become decisive factors for determining success.

NEED FOR MECHANIZATION

The Mechanization began to show up in the 1960‘s in Construction projects. Initially, government

bodies such as Ministry of Transport (MOST) AND Public works Department (PWD) imported

equipments and hired them out to contractors for execution of works. The market was accordingly

limited in scope. In the 1980‘s, the projects began to be increasingly granted on turnkey basis. Project

sizes also became larger and external funding agencies started mandating the use of appropriate

equipments for works funded by them. Gradually, one of the criteria for Pre-qualification of contractors

became the ownership of equipments. Faster Project execution required state-of-art equipment. The

average unit cost of construction equipment in the construction works became around 15 to 20%.

With the demand for Labour and increase in Labour rates there is a need to have a look into the entire

construction activity and its impact on the final project cost. The advanced economy has taken

advantage in terms of Mechanizing the construction operation by adding more content of pre-fab

works, precast sections , introducing modular design concepts and adopting industrialized method of

construction. The advanced economy had forced them to Mechanize a good proportion of their

construction activity due to shortage of Manpower and to meet the demands of the clients for

completing jobs within the scheduled time. In India though we claim to have resorted to high

mechanization particularly in some of our irrigation and industrial projects, still full scale mechanization

is yet to be achieved. The time is however, not far off when a contractor who does not keep himself

abreast of new construction equipment and methods of planning and construction may discover

himself to be out of business.

A problem which frequently confronts contractor as he plans to construct a project is the selection of

most suitable equipment. He should consider the money spent for equipment as an investment which

he can expect to recover with a profit during the useful life of equipment. A Contractor does not pay for

construction equipment, the equipment must pay for itself by earning for the contractor more

money than its cost. Unless it can be established in advance that a unit of equipment will earn more

than the cost it should not be purchased.

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A Contractor can never afford to own all types or sizes of equipment that might be used for the kind of

work he does. It may be possible to determine which kind and size of equipment seems to be most

suitable for a given project but this information alone will not necessarily justify the purchase of

equipment. Perhaps the project under consideration is not large enough to justify the purchase

because the cost cannot be recovered within the completion period of the project and it may not be

possible to dispose of the equipment at the completion of the project at a reasonable price. A

contractor may own any type of equipment, but, considering the probable heavy depreciation for the

proposed equipment and the uncertainty whether it can be used on future projects, the apparently ideal

equipment may prove to be more expensive than the equipment now owned by the contractor.

The foremost important decision is to select the most suitable plant and equipment which can pay for

itself and determine the number and type, essentially required for the newly acquired job. A great deal

of information and specifications, production capacities, capital costs and costs of operation and

maintenance are available in the supplier‘s manuals for various types of equipments. A well

experienced equipment engineer/planner comes handy in the decision making.

Projected Demand for Construction Equipment in India

(Number of units)

Product Group 2005-06 2015-16

Hydraulic Excavator 9350 14000

Excavator Loader 10450 16700

Front – end loader 4837 7255

Crawler tractor dozer 2450 3675

Mobile Cranes 3870 5805

Vibratory rollers (Soil & Asphalt) 1340 2345

Road Rollers (Static) 1200 1400

Asphalt Pavers

4.1 Mechanical

4.2 Hydrostatic

400

160

500

200

Motor Graders 150 175

Hot Mix Plants 700 800

Source: http://www.tradeport.com

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Chapter 2 : Economics of Construction Equipments

1. General :

Construction Equipments have become essential and inescapable part of modern construction.

The variety is vast and is increasing due to globalization of Economy. However these modern

sophisticated equipments are very costly, involving huge capital out-lay. They have a useful life of

a number of years. In order to optimize the procurement and utilisation of the Construction

Equipment, it is necessary to understand the various factors of cost of using the equipment.

2. It is customary to group these cost elements in two groups & various subgroups as given below.

a. Ownership Cost

i. Depreciation

ii. Interest

iii. Insurance & storage

iv. Transport & setting up

v. Miscellaneous & Overhead

b. Operation Cost

i. Fuel & Energy

ii. Lubricants

iii. Spares & Consumables

iv. Operating Manpower

v. Repair Man power

vi. Miscellaneous & overhead

c. I. The ownership costs are in the nature of fixed costs as they have to be incurred

irrespective of the quantum of use. These are real costs as far as an organization is

concerned but they are notional for a site. They are also called as proforma charges.

Many project executives are not aware of these.

ii. The operation costs on the other hand are directly related to the quantum of use &

efficiency of the equipment. These costs are normally incurred by the sites and are too

apparent & real.

3. Depreciation :

a. The concept of depreciation basically means gradual reduction in intrinsic value of

equipment due to usage or time. The concept was historically evolved first for building / plant

and then applied to Machinery, Construction Equipment & Vehicles. It should be appreciated

that in spite of care, maintenance & repair, machinery reduces its efficiency and hence the

value depreciates. This is a major element of ownership cost of equipment. This is a national

or book expenditure.

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b. The Book value is arrived at by reducing purchase cost by depreciation. This also generally

reflects the market realizable value (i.e. price) were the equipment to be sold. In a high

inflation or price rise economy, this needs to be applied with prudence. There are instances

where old (but working) Vehicles & Equipment could be sold at prices higher than the original

purchase prices.

4. Straight Line Method of Depreciation :

a. In this, a fixed annual value of depreciation is decided for a type of machine or for all machines

as such by an organisation. Thus the amount of annual depreciation is fixed irrespective of the

years spent i.e. used life of equipment. This is the method most prevalent in Government

departments and some of the Public / Private sector companies.

b. The formula is

Dm = P – S where, Dm = Annual depreciation in mth year

n P = Purchase price S = Scrap price

n = useful life of equipment in years

Straight line Method of Depreciation

5. Sum of the years method – This is a

method which gives faster depreciation

i.e. more absolute value of depreciation

during initial years. It is an ingenuous

method, simple to use but little difficult

to comprehend. It can best be

illustrated by an example

i) Purchase Cost = 12 lakhs

ii) Residual value = 2

lakhs

iii) Total Depreciation = 12-2 =

10 lakhs

iv) Life = 10

years

v) Sum of years (balance life

during any year) =

10+9+8+7+6+5+4+3+2+1 = 55

i.e. 10x11/2 = 55

vi) Dep. In 7th year = 10 x 4

= 0.72 lakhs

55

Year Value at

start

Depreciatio

n

Value at

end

1 12 1 11

2 11 1 10

3 10 1 9

4 9 1 8

5 8 1 7

6 7 1 6

7 6 1 5

8 5 1 4

9 4 1 3

10 3 1 2

Year Multiplying Factor Depreciation Book Value

0 0 0 12

1 10/55 1.81 10.19

2 9/55 1.63 8.56

3 8/55 1.45 7.11

4 7/55 1.27 5.84

5 6/55 1.09 4.75

6 5/55 0.90 3.85

7 4/55 0.72 3.13

8 3/55 0.54 2.59

9 2/55 0.36 2.23

10 1/55 0.16 2.07

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Depreciation by Sum of Years Method

6. Diminishing balance method - This is also called Written Down Value Method. In this the

percentage of depreciation is fixed rather than the amount. This percentage is applied to the Book

Value at the end of previous year (i.e. beginning of current year.)

The formula is

Dm = R x (BVm-1)

Where

Dm = depreciation in mth year

R = percentage annual depreciation decided

BV = Book Value

This percentage is decided by the organisation. It is most common to take this as 20% to 30%.

Depreciation by Diminishing Balance Method (20%)

Note - Since we have assumed the residual value to be Rs. 2 lakhs, the depreciation has not

been charged in 9th & 10th year.

7. The concept of depreciation has the following aspects or purposes.

a. To reduce the book value of equipment to tally with the intrinsic value.

b. The book value should tally with the expected market value (in case we are to sale the old

equipment)

c. Create a sinking fund so that when the current equipment outlives its useful & economic life, a

new equipment can be purchased.

d. To meet the legal requirement of Income tax act & Companies act etc. The companies act

provides for depreciation both on WDV (Diminishing balance) method as well as straight-line

method. It lays down the parameters and directs that there are the minimum amounts. Income

tax Act/rules provide only for WDV method and that too only as prescribed. Not less & no

more.

8. Interest: - This element is considered on the assumption that money for the purchase of

equipment has been borrowed from the Banks or other Financial Institutions. Many finance

executives would like to consider that the funds have come from working capital and charge

Year Initial Book Value Depreciation Final Book Value

0 0 0 12

1 12 12 x 0.2 = 2.4 9.6

2 9.6 9.6 x 0.2 = 1.92 7.68

3 7.68 7.68 x 0.2 = 1.53 6.15

4 6.15 6.15 x 0.2 = 1.23 4.92

5 4.92 4.92 x 0.2 =0.984 3.93

6 3.93 3.93 x 0.2 = 0.787 3.149

7 3.14 3.14 x 0.2 = 0.629 2.52

8 2.52 2.52 x 0.2 = 0.504 2.016

9 2.016 2.016 x 0.2 = 0.403 2 (1.613)

10 2 2 x 0 = 0 2

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interest @ 15-20% pa. It can also be argued that the funds have come from share capital or long

term loans and interest should be charged @ 10-15% only. Even if the actual money is not

borrowed, but taken from the company‘s reserve, one has to consider the ―loss of opportunity‖ as

these funds could be invested elsewhere.

9. Insurance & Storage :

As the Construction Equipment is very costly, it is customary to insure these so that in case of

loss, the machinery can be replaced. The Insurance premium depends on the risks covered, type

of policy, the organizations past record, clients (tender) conditions & so on. It is sufficient to

remember that insurance charges are not related to utilization of the equipment.

Once equipment has been procured, it has to be stored properly. It may involve construction of a

Garage or purchase of Tarpaulin for storage but some costs are to be incurred. These are also not

dependent on the usage of the equipment

It is thus customary to club these charges and to charge them as a percentage on annual basis.

These are normally related to Book Value.

13. Transportation & Setting up charges :

a. In addition to actual purchase cost, to bring equipment to site & to make it ready for

production, transportation & setting up expenditure has to be incurred. The latter are

considerable for static plant and include foundation, area development, Erection &

Assembly, trial run etc.

b. It is customary to add these to the procurement cost after the expenditure is actually

incurred. This is done by capitalizing the expenditure. Some organizations may however

include this to the running cost of a site.

c. Such expenditure has also to be incurred when equipment is transferred to another site.

This may be capitalized or included in the running expenditure of the new site.

14. Miscellaneous – Overhead Expenditure – This includes charges for security, pro-rata expenditure

of purchase department etc. The practice varies from organization to organization. The amounts

are generally small and we need not go into these.

15. FUEL: - This is an item of large value and part of operating cost. In cases of plants like Asphalt

Mixing plants or Tar boiler this includes the cost of Furnace or Light Diesel Oil used for heating. In

case of electrically operated plants this includes the charges of Electricity. These are charged at

actual as & when the payments are done. Petroleum products can be very easily booked to the

individual equipment. In case of Electrical equipment unless each equipment is provided with a

meter (which is rare), the charges are notionally distributed on estimated basis.

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16. Estimating Fuel costs :

a. While these charges are to be booked at actual, at the time of estimating an educated

guess has to be made. This is also required to be made while evaluating the different

alternatives of equipments at the time of procurement.

b. In case of petroleum products, these can be estimated based on the data made available by

the manufacturers. In absence of that, the thumb rule of ―0.15 litre/HP/ hour of Diesel /

Petrol‖ can be used for estimating.

c. In case of electrically operated plants the total, HP/KW capacity coupled with power factor is

the obvious solution. Similarly for Hot mix plant the manufactures figure are the best.

d. However the above are many times inaccurate & misleading. They also vary on factors like

operating efficiency, condition of the equipment, ambient temperature, moisture content of

raw materials etc. As fuel consumption (and cost) is a major element of equipment cost,

and are controllable by management an accurate & detailed system of accounting, data

generation & evaluation is a must.

17. Lubricants :

a. This head covers the cost of oils like Engine oil, Gear box oil, Differential oil, Hydraulic oil

and Filters for these. The consumption is directly related to the usage. It covers

consumption for replenishment (top-up) as well as periodical replacement.

b. As in the case of fuel, the best way is to go by manufactures data coupled with planned

usage. In absence of this, the thumb rule is to take the cost of lubricants at 5-7% of the

cost of fuel.

c. Due to constant development of the technology, better lubricants are available. While on the

one hand these are costlier, the life between changes is more. They also contribute to

improving performance & life of the machinery. Many times excess consumption results

due to extraneous factors like spillage, breakage of pipe lines / oil seals & so on. In some

cases there may be less consumption due to non availability of oil. (This of course is bad

for the machine). Hence accurate record keeping and monitoring is necessary.

18. Spares and Consumables :

a. Spare parts & consumables are very important from the point of view of Mechanical

Engineers. Their technical expertise has a direct bearing on this. The mechanical engineers

expertise is also required in estimating the requirement, deciding the quantum of assemblies

to be procured, stocks to be maintained & so on.

b. By consumable we mean here consumables required for repair work. The range is large. It

includes items of following types.

i) Batteries ii) Tyres

iii) Electrolyte & distilled water iv) Emery papers

v) Welding Electrodes vi) Electric wires

vii) Cotton waste viii) Paints & Varnish

ix) Coal x) Hand tools

xi) Special tools xii) Insulation tape

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xiii) Armature rewinding wires xiv) Steel / Copper washers

xv) Nuts & bolts xvi) Gasket papers & Sealants

c. The best way of estimating the requirement of spare parts during a period (say 12 / 6 / 3

months) is to do extra polation based on past data. While doing this, factors like quantity

of equipment held in past & future, condition of the equipment, planned usage, quantum of

repair (like overhaul etc) done & planned, budget etc. have to be considered. For

estimating purposes, the guide lines given by manufactures (They very rarely give details

for life time consumption) for initial spares can be used. For later years and for total

consumption, one can take guidance from Plant & Machinery Committee report of the

Central Water & Power Commission. It is reproduced as Appendix I. No such guidelines

are available for expendable stores. While using their guidelines of CWPC, the equipment

cost (Purchase Cost / Book Values) needs to be notionally increased to take into account

the effect of inflation.

d. For estimating the requirement of spares, at least reasonably correct & exhaustive data is

a pre-requisite. While effect of would be loss, both by way of interest & overstocking costs

& actual loss if surplus items have to be sold off, can be visualized easily, the effect of non-

availability are more serious & hidden. This is because not only it is very costly to have

equipment in non-working condition but the effect on connected work & project schedule

can be grave if not colossal. It may be prudent to err on safer side. In most cases it is

difficult to quantify the probable loss vis-a-vis inventory cost.

19. Operating Manpower :

a. The requirement of manpower is mainly based on site experience & work-study. There may

be some variation from region to region & organization to organization. The following general

guidelines can be followed. Some exceptions have to be made.

i. Small M/c - One helper or labor per machines. Jackhammer should need a driller.

ii. Minor M/c - One operator / driver

iii. Major M/c - One operator + One helper

iv. Major plants - This includes Batching plants, Hot mix plants etc. There may need for 2 or

more operators & 2-3 helpers.

b. The quantum & wages shall also depend on the following factors

i. Educational / Technical qualifications & levels of experience

ii. Work culture

iii. Cost of idle equipment in case of non-availability of operating staff.

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20. a. Unlike the manpower for operating equipment, it is difficult

to estimate the repair man power. Requirement of repair man power has a relation to ―repair

content‖ of an item of equipment. The repair content depends on the size (HP) of the

equipment & the nature of the equipment. It also depends on the quantum of the repairs to be

undertaken i.e. whether all repairs are to be undertaken at site or if a separate base repair

establishment is available in the organisation and only field repairs are to be done at site. The

quantum of repairs also depends on the age of the equipment. Old equipment will involve

more repairs and so on. The quantum of repairs (and time frame) would be less if ―Unit

Change System‖ is prevalent.

b. While in some organisations, a proper and objective system / yardsticks have been evolved, in

majority of the organisations, an ―Ad-hoc‖ system is in vogue. In this, the requirement of man

power is planned / demanded by an executive and is approved by another executive. Both

these are done based on personal experience & judgment of the executives concerned.

c. A systematic approach is adopted by Army (Engineers) and Border Roads organisation. In

this, the repair content is decided in terms of ―Repair Unit‖. Obviously it varies from equipment

to equipment. A truck is 1.5 Ru, Crawler Tractor (up to 100 HP) – 3 Ru, Motor Grades 4 Ru,

Crawler Tractors (100-300 HP) – 4 Ru & so on. The capacity of a mechanic is taken as 9 Ru.

and the total repair load of equipment is matched to the total capacity of mechanics.

d. The quantum of allied trades is decided on the basis of one allied trades man per so many

mechanics. The necessity or otherwise of these allied trades men depends on the total fleet of

equipment, availability of market repair facilities etc. It also involves procurement of allied

machinery like lathe, welding transformer, Gas welding equipment, Battery changing

equipment etc.

e. A suggested yard stick for deciding repair man power is given at Appendix –II

21. Miscellaneous & Over head: - This heading includes cost of facilities like arrangement of storing

& issue of fuel, office staff for accounting & data generation for Equipment management & so on.

No norms can be laid down for this. The estimation has to be based on the judgment and the

systems / practices in vogue.

22. To summarize, in absence of the organization‘s own and manufacturers data, the following yard

stick can be adopted for a given mixed fleet of equipment.

i) Depreciation - 20% - 30% the Book Value of

equipment.

ii) Interest - 12 to 15% of Book Value

iii) Insurance & Storage - 1% - 1.5% of depreciation.

iv) Fuel - 0.15 liters / Hp /Hr.

v) Lubricants & tilters - 10% of fuel cost

vi) Spares - 10 to 15% of Book Value.

vii) Operation & repair man powers

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a) Operators -Rs.4000 – 6000/month

b) Mechanics Rs. 5000 – 7000/ month

c) Foremen Rs. 6000 – 9000 /month

ACCOUNTING

23. This covers accounting of equipments, spares, cost of operation & repair and cost of output. As

pointed out earlier, elaborate & accurate accounting, data generation and its use for control is

very essential for good Equipment Management. The various systems & concepts shall be

discussed in the following pares. The actual system shall vary from organisation to organisation.

There can‘t be an ―ideal‖ system. However a good system should give the answers to the

following questions.

i) What is the cost of a unit of output of given fleet of one type of equipment per period, at a

site or of the organisation?

ii) What is the cost of a unit of output of each machine? How does it change with life in

hours/years, site etc.?

iii) What should be the economic life of a type of equipment?

iv) What is the fuel cost of equipment? How does it compare in different makes & vintage of

equipment?

v) What is the cost of spares spent on the upkeep of a machine? How does this vary with

make to make, model & vintage of a machine

vi) Is the operating & repair man power adequate, are there any surpluses, are any machines

idle for want of man power, what is the cost of such idleness. Is overtime reasonable?

vii) Is the planning of project & equipment realistic? How the actual compare with planning? Is

some equipment idle for wanted of work front, did the construction schedule get affected

due to non-availability of equipment?

viii) Was the quantum of spares procured as planned? Was it adequate? are there any

surpluses?

24. Accounting of The Basic equipment

a. Construction equipment is also a fixed asset as per Company & Income Tax laws. While

Finance & Mechanical departments should have a common system, these can be separate also.

In order to identify equipment, it is necessary to identify each piece by a unique code. This can

be referred to in all documents like Logbooks, History books. Returns, ledgers as well as

painted/marked on the equipment. Normally each equipment does have a manufacture‘s serial

no. /chassis no. & others details. This serial nos. is the basic identification. An Alfa-numeric

code is easy to operate.

CM – I, CM – 2 Concrete mixer 1, 2

HS – 4, HS – 5 Hydraulic Shovel 4, 5

RR – 2, RR – 3 Road Roller 2, 3

25. The following basic information of the equipment shall be available in head office as well as other

places & up dated periodically

i) Code No ii) Chassis / Serial No

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iii) Engine Serial No.

iv) Auxiliary Equipment Serial No.

v) Technical Data – Equipment.

aa) Make

bb) Model

cc) Capacity / Size

vi) Technical Data – Prime mover

aa) Make

bb) Model

cc) Capacity / Size

vii) Purchase / Procurement Date

aa) Name & Address of Supplier

bb) Purchase Order no & date.

cc) Purchase Cost

dd) Tpt + assy Cost

ee) Erected Cost

viii) Utilization / repair Data

ix) Work Done

aa) Period, Qty, Acct. unit

bb) Cost Centre, contract number etc.

cc) Details of output/type of soil, size

of aggregate etc.

Year Book

Value

Utilisation

HBs /Km

Out Put Cost of repairs

Spares Others total

29. Accounting of Spares

a. Spares form .a very important item of repair expenditure. The range is very vast, price & quality

variation is large and the past consumption is the main basis for planning for future. Few more

important aspects of a spare parts are

b. The manufacturers part no (identifiable from the part catalogue) is the main identification. If the

part no is misplaced or item kept in some incorrect place it is almost impossible to identify &

locate it. Many parts look similar but because of minor differences in dimensions or material

properties, these can‘t be inter chargeable. On the other hand there may be major differences in

materials or dimensions but the items would be inter changeable.

c. The word ―Spare Part‖ also include assemblies. There are not consumed as such. These can

be in turn repaired many times.

d. Unlike consumable materials, the spares (in general) are not consumed but old items can be

taken back & do have considerable value (price). It is also necessary to account for old part

from the point of malpractice.

e. In view of above the following record should be kept for each item of spare.

I

) Part no

ii) Nomenclature

Equipment

i) Model

ii) Item Code

iii) Location

iv) Interchangblity

v) ABC Catagory

vi) HML Category

f. Format of Ledger page/Cardex

Date From Receipt Issue

To S R u/s S R u/s

Balance Purchase Rate Issue Rate S.B. Rate

S R u/s

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26. Costing of Equipment usage: -

a) Manufacture Estimate one of the methods of planning & evaluating Equipment

Management Cost is to prepare Manufacture estimate. This system was common in

CPWD & Hydroelectric projects. In this each equipment is considered separately.

Target utilisation is determined / estimated and cost per unit of output is arrived etc. The

concerned activity / job is debited the cost per hour of usage at the end of Every

week/month/quarter. Based on actual utilisation the estimate is revised at the end of

financial year & the booking done adjusted at the end of the financial year.

Evaluation -?

b) Usage rate:- The fact that ownership costs one fixed and the actual user/site does not have

any direct control on these is utilised in this concept of Usage Rate. This is rate in terms of

Rupees per Hr / Km of equipment & vehicles. It includes all the ownership costs and though it is

given for one quantity of equipment it is calculate for each type & make of equipment. This is

based on some hours/kms utilisation of equipment per year and fixed (assumed) life in terms of

years / hours. This was followed by BRO in pre-computer days.

Evaluation -?

31. Project Estimates

i) At the time of preparing project estimates as well as tenders,

the cost of work to be done by machinery has to be taken into account. While detailed study of

the project for leads, quality of out put & so on has to be done in as much detail as possible, in

many instances the details are not available and an educated guess has to be made.

ii) After award of work, during detailed planning i.e., the equipments, methodology of construction,

construction schedule etc. is done and along with specific equipment detailed estimates are

prepared.

32. Log book – This is a document used for day-to-day utilisation of equipment. It gives (apart from

equipment identification) such details as operators record, fuel consumed, Hrs utilised, output,

details of job, where utilised (i.e. cost centre etc), Names / signatures of operating /user

supervisor / mangers & operator, period of Breakdown & reasons, period of idleness & reasons &

so on. In effect it is the interface between Mechanical & User (civil) sections. It may also contain

operating & maintenance instructions.

33. History book :- a) This is the main record of mechanical section for each equipment. It is

also an important record for equipment management. It remains in the mechanical section &

is transferred from site to site along with the equipment. It normally contains the following

types of information.

i) Equipment record – Code, details of procurement, Technical Specification, Capacities of

Fuel/ oil /Lubricants etc.

ii) Transfer record.

iii) Tyre fitment record.

iv) Tyre rotation record

v) Battery record

vi) Maintenance record

vii) Repair record.

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viii) Abstract of utilisation

b. i) The maintenance record includes the schedules & specifications of lubricates &

changes of filters.

i) Repair record is the most important for Mechanical Engineers. It would contain all the

details of spares / assys used & cost there off, time taken for repair, details of repairs

done from market, changes of majors assemblies like Engine, Torque Converter.

Changes of oils & filters, cost of repair manpower & so on.

34. Ancillary records – The mechanical section or stores section may have to maintain many

other records like Job Cards, Fuel ledger, Repairable Assys ledger, Site store ledger, Fuel

requisition slips. It is not proposed to list all there as the requirement is basically of

Mechanical Engineers & varies from organisation to organisation.

35. Computerisation – It would be clear from above that the data required relating to Equipment

is maintained in various sections like planning, purchase stores, users, finance, mechanical &

so on. Before advent of computers there used to be lot of duplication and in many cases it

was a project to compile and present it in a meaningful way. Now with use of computers &

specially with concept of LAN, it is possible to feed data at different locations, bring out

reports required by each section and bring managerial reports by combining the various

information. Ultimately the system has to answer these basic questions

i) Has the machine done the work in time & cost planned and if not why

ii) Has the machine total cost been as per plans and if not why

iii) Should we continue to use this machine or call it BER & dispose off.

36. Incentives

a) It would he clear, that while estimating cost of operation / out put of equipment, many

indeterminate factors have to be included based on estimates and educated guesses. An

effective managerial system can reduce their uncertainties, and make them more accurate

progressively. There is considerable scope for Incentive Schemes. The incentive schemes

can be primarily in 2 areas.

i) For operation – So that the available equipment shall be intensively utilised. This can be

aimed primarily at users i.e. operating staff / sections. and

ii) For repairs so that the cost of maintenance (repair) is reduced. This has to be aimed at

mechanical staff / section. Cost of repairs (manpower & overhead), cost spares

consumed and off road (idle due to repairs) period has to be part of such a scheme.

b) Many agencies / sections / staff are involved in both the aspects. There is intrinsic tendency

& scope to blame others and to resort to short sited decisions to claim incentives. Thus lot of

thought and concerned persons‘ involvement has to go in to make it affective & clear. The

schemes should be linked to MBO (if in vogue). These should be based on existing data

instead of generating separate data for the incentive schemes as such.

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Appendix – I

Para 18 – 417/2

LIFE & REPAIR PROVISION OF EQUIPMENT (CWPC)

S.No

Equipment Life of Equipment Repair Provision (%age

of cost of Equipment)

Re

-marks

Category

Capacity

Years

Hours

1 2 3 4 5 6 7

1. Excavators Shovels &

Draglines

Upto 1.5 cuyde.

1.5 to 3.0 (diesel)

Above 3.0 (diesel)

2.5 to 4 (elect.)

4 cuds. & above (elect)

10

12

15

15

20

12,000

15,000

25,000

25,000

25,000

150

150

150

150

150

2. Bucket wheeled

Excavators

20 40,000 150

3.

Dumpers

Bottom Dumpers

Rear Dumpers

Upto 20T

20T to 50T

Upto 15T

15T To 35T

above 35T to upto 50T

8

10

8

10

12

10,000

16,000

10,000

12,000

15,000

140

140

140

140

140

4. Scrapers Upto 10 cuyds 8 9,000 150

5. Tractors

a) Crawler

b) Wheeled

upto 100 H.P.

100 to 300 H.P.

above 300 H.P.

upto 75 H.P.

above 75 H.P.

8

10

12

8

10

9,000

12,000

16,000

12,000

15,000

200

240

240

150

150

6. Graders 10 12,000 200

7. Loaders

Crawler

Wheeled

Belt loaders

Reclaimers & stackers

10

10

16

20

12,000

15,000

20,000

30,000

200

150

70

70

8. Compactors

Vibratory Rollers

Smooth Drum Rollers

Smooth drum vibratory

rollers

8

8

8

8,000

10,000

8,000

150

80

150

9. Canal trimmer and

Lining equipment

above 200 cud/hr.

16 20,000 100

10. Drills

Core Drills

8 20,000 100

11. Tricone rotary Drills 10 10,000 80

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A. Repair unit of Plant & Machinery

Sr.

No.

P&M RU Sr.

No.

P&M RU

VEHICLES

1. Car 1 2. Jeep 1

3. Truck 7 Ton 4x2 1.5 4. Truck 7 ton 4x4 2

5. Recovery veh. Medium 2.5

EXCAVATORS

1. Shovel 1m3 3 2. Shovel 1 to 2m3 4

3. Bucket Excavator 5

DUMPERS

1. Bottom dumpers upto 20 ton 3 2. Bottom dumpers 20 to 50 ton 4

3. Crawler above 300 HP 5 4. Wheeled upto 75 HP 3

5. Wheeled above 75 HP 4 6. Motor grader 4

LOADERS

1. Crawler 3 2. Wheel 3.5

COMPRESSORS

1. Diesel upto 300 cfm 1.5 2. Diesel above 300 cfm 2.5

3. Electric upto 300 cfm 1 4. Elect. above 300 cfm 2

BATCHING PLANTS

1. Portable upto 15 Cum / hr. 2 2. Stationary 15 to 50M3 / hr 2

3. 120 KVA above 3

B. I. Capacity of each mechanic is taken as 9 Repair units

ii. The composition vehicle mechanics. Heavy Earth Moving Machines and fitters etc. shall

depend on the types of machines.

iii. The capacity may be decreased if major repairs are also to be undertaken and increased

if market repair facilities are to be utilized for field repairs.

C. The allied tradesmen‘s requirement can be assessed on the formula given below.

I. Auto Electrician 1 per 5/7 mechanics

ii. Black smith / TCS 1 per 10 mechanics

iii. Welders 1 per 10 mechanics

iv. Turner / Mechinist 1 per 10 mechanics

v. Store Keeper 1 per 10 mechanics

vi. Foreman / JE 1 per 5 mechanics

vii. AE 1 per 10-15 mechanics

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CONSTRUCTION EQUIPMENT DEFINED.

― Construction equipment/s are machines to give desired / designed out put with available input,

using mechanisms and machine elements applying principles of mechanisms like

1) Lever And Fulcrum Mechanism

2) Cranking Mechanism

3) Quick Return Mechanism

4) Differential Mechanism.

By Using machine elements like pulleys, belts, ropes chains, levers, wheel and axles, gears,

clutches, brakes etc. In one form or in combination of forms/ arrangements. ‖

Construction is the ultimate objective of a design and machines make accomplishment of that objective

possible. Machines for construction must be selected in such a way that they must economically match

machine capability to specific project construction requirements.

Equipment is an economic investment and contractors must be able to apply the appropriate time

value analytical formula to the decision process of machine purchase and utilization. The proof of how

the planner understands the work and coordinates the use of the company‘s equipment is in the

bottom line, when the contract is completed – is it at a profit or loss.!

At what levels what needs to be taught and learnt with regards to construction equipment.

Training levels:

A) skills:

Skill training involves , learning the theory , mechanism and practicals of the const Eqpt.

For whom: this is for operators and supervisors.

B) knowledge:

This involves the basics, understanding the task performed by each piece of equipment what is basic

and what is secondary tasks performed by each equipment, constant and variable factors in equipment

output, factors effecting the output, data for planning i.e. Knowing the equipment capability, knowing

the outputs reqd for project and considering various external factors, assessing the equipment

requirement.

For whom: for engineers from 2 years to 12 to 15 years experience.(6-8 or 8-10)

C) strategies:

1. Selection of equipment

2. Various equipment procurement options.

3. Owning, hiring , leasing or hire purchase.

4. User charges , hiring rate.

5. Replacement decisions. Study various replacement models.

Meant for managers, senior executives of the companies who are in the decision making levels of the

company with regard to procurement of const. Eqpt, plant and machinery.

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Why go for mechanising construction: ??

1. Go for construction equipment to substitute man power with machine power – this is termed as

mechanization

2. Go for construction plant for reducing or eliminating the interference of human being in operation by

auto loading, unloading and transfer of material – this is termed as automation

3. The above 2 are primary purpose of deploying const . Eqpt. The secondary objectives are.

4. To increase output

5. To improve productivity of resources- to achieve better production at economic cost.

6. To reduce project duration

7. To achieve the desired quality of work- repeatability, consistency, done effortlessly

8. To reduce accident on site – since the labour force on site is less.

9. Can be more dependent as labour regularity, availability and punctuality cannot be ensured.

10. Certain projects like world bank projects are offered only when you have adequate machinery of the

desired capacity and also it is owned by the contractor.

Design of Maintenance Systems

Designing the maintenance systems for an organisation is a difficult and complex task, as it has a

number of factors which interact with and affect it. This is the ' main challenge and task of the

Maintenance Manager, which he has to perform with extreme care and caution. As a scientific

approach is imperative for the success of designing a maintenance system, the first step is to carry out

the criticality analysis of plant and machinery which can guide about the extent and the kind of

maintenance effort needed for a particular type of machine or facility. Based on this, a judicious blend

of breakdown, planned/preventive and predictive maintenance systems can be designed.

The other factors that need to be carefully considered are the internal facilities that need to be created

to support the designed systems. Also, their cost, and the possibility that they have to depend on

external sources, like OEM (Original Equipment Manufacturer) and the facilities offered by them, its

location, proximity to own factory location, lead time needed to obtain their help and also the facilities

available in the geographical location for contracted maintenance and their availability and quality. In

certain situations, due to the lack of facilities being available externally or due to certain internal

factors, the organisation may be forced to opt for creating its own support system and resort to depend

on internal maintenance capabilities alone. Thus, on an aggregate, the maintenance planning effort will

depend largely on the size of the organisation, unit location, and connected logistic problems, local

availability of maintenance infrastructure facilities, level and nature of technology involved, secrecy

needed (for Defense or atomic energy plants) and skill levels required. Due consideration has also to

be given to designing of the organisational structure and the extent of centralisation and

decentralisation that will be required to meet the needs of the system so designed.

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CRITICALITY DETERMINATION

Criticality determination is the starting point for planning of maintenance effort. And it is quite obvious

that more critical the equipment, the more maintenance effort it will warrant to keep it in a serviceable

condition. It is apparent, therefore, that a concerted effort will have to be made at the earliest stages of

the Endeavour, if a meaningful plan of action is to emerge for implementation. For it is this criticality

which will also determine as to which equipment, machinery or plant will requires the greatest or the

least amount of care and attention, and the ■mount of attention each grade of criticality will require.

The effort made towards categorisation will show that some of the equipment And machinery will

require different types of maintenance:

a) Predictive maintenance (which could also be called condition monitoring) or preventive

maintenance (As both predictive and preventive maintenance efforts are very expensive, it

becomes imperative that careful sifting be done so M to not allow those equipment, machinery and

plant which do not require so much maintenance and care to be mixed up with this group

erroneously.)

b) Normal planned maintenance,

c) Breakdown maintenance (which has to be carried out only as and when the need arises; this kind

of ad hoc maintenance work should only be recommended for the least critical categories of

equipment).

In order to be able to achieve maximum plant availability—most economically, the able planner

will have to device a system of maintenance, which will be a judicious mix of the different types of

systems for specific equipment as per criticality determination.

Criticality determination is the process wherein one attempts to scientifically end

systematically pin-point and list the most important steps/organs of a process, plant or factory by

determining how important is their healthy functioning for the well-being of the whole system so that

they can be given correct weight age in terms of care and maintenance.

However, it would be worthwhile to keep in mind the fact that this is an extremely delicate and difficult

task. In order to arrive at a judicious and cost effective assessment of the task ahead, all the skill,

experience and expertise of the maintenance managers will have to be pooled together. Even so,

criticality Cannot be determined by a one-time effort, for solutions to the problems will •merge from

the evolution of thought process based on facts and figures over • period of time. And the correct

precedence of criticality can be determined only after a considerable amount of trial and error.

Down Time Costs

The first question that comes to one's mind when a breakdown occurs is: How expensive is the

breakdown? For all assessments eventually are cost related; hence let us begin with this important

question.

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To know the extent of breakdown expenditure, one has to accurately work out the exact cost,

costs accruing from a breakdown could be immediate as well as far-reaching. Cost of lost production,

labour cost, cost of replacements and spare-parts come immediately to one's mind. However, the other

aspect, namely, 'impact.' cost Could well be even more and needs to be taken carefully into account

For example, along with the cost of loss in production one must calculate cost in terms of the idle time

of the production labour, and of all those others who have been rendered idle by the same breakdown

down-stream .Then, there could be the cost to be paid as penalty for delayed delivery of an order, or

worse still, the cost of an order being cancelled. Further costs may be incurred with an urgent need to

air freight a particular indispensable spare part or some necessary raw material to get on with the work

of rectifying the breakdown.

The actual coat of down time can be calculated only by adding the time frame by the machine to be

repaired and to be put back into operation.

Once all these parameters have been calculated, then an evaluation will have to be made by top

management as to what they would consider as very high cost and what would be high cost, and so

on, in a continuing order. Having the problem from all the angles and with the table of cost of down

lama before them, the top management will then take a decision about the cut-fJT point, where the

cost of down time will place a particular piece of machinery In the critical or vital category.

SEVERITY OF UTILISATION

The demand made on a machine for a particular service that it provides to its tiers, and the extent of its

loading or utilisation per day, can be termed as severity of utilisation. Its critical relationship with the

product or production output {Rust be ascertained and gauged correctly.

Standby Availability

For critical machinery, it is always desirable to have a parallel system, which can be put to use in case

of equipment failure. This is called standby availability, and is an important factor to be considered

while designing maintenance systems.

Downstream Effects

Downstream effects are the important criteria as they can have serious long-term Implications. Let us

take the example of a chemical plant where, say, a slurry MM been prepared, which needs to be

continually stirred and allowed to chemically affect for six hours at a fixed temperature. If a breakdown

were to take place upstream in a critical machinery at any time during this predetermined phase, often

not only would the entire slurry go waste, but it could also lead to shut down of the chemical reactor

itself, for as a result, it would in all probability be aiding a thorough chemically processed cleaning or

worse still a relining of the Vessels and vats where the slurry had gone waste. Thus, we can see how

an upstream breakdown has far-reaching repercussions downstream. For apart from the product

cooking in the vat going waste, the repairs and refurbishing bills, the tosses to be borne due to loss in

production time and all its other attendant Cumulative expenses can lead on to a total shut down. The

financial loss due to non-delivery of goods and so on, can prove to be a rather costly for any industry. It

is obvious, therefore, that a critical area such as this needs to be given due Consideration.

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Hazards Involved In the Event of Failure

In the event of failure, breakdown or malfunctioning, certain machinery and plants can bring terrible

hazards to man, his property and even his environment, for the fall-out of such failures can be very

dangerous, damaging and destructive. The hazard could be in the form of poisonous, toxic or

inflammable gases, or in the form of torrents of engulfing water unleashed upon the unwary, by the

malfunctioning of a simple thing like a flood-gate. However, while talking of hazards which may occur in

plants and factories, one must concede that in case of a failure it will be the plant personnel

themselves who will be affected first.

Skill Availability

There could be certain items of equipment in a complex, complicated and technically sophisticated

modern plant which is important in the chain of production requirements. Though its welfare is vital to

the well-being of the operation, it is possible that the maintenance organisation may not yet be able to

acquire the necessary skills to repair or rectify these components, for that matter they may not even be

quite confident about their diagnostic abilities to pin-point a fault as and when it arises.

With the rapid advancement in technology, skills required to cope with the state of the art technology

often lags behind, the effects of which are felt by all areas and functions. However, in the case of

production, the benefits positively outweigh the negative ones. Initial training is a must for the

production personnel before they start working on any new machinery. However, soon they get lot of

praise for the results and outputs consequent to harnessing new technology. But fragile machines with

highly flexible controls and stupendous levels of productivity may be easy to handle and control, but

can prove to be very difficult when in need of repairs and rectification. And normally with brand new

machines in hand, little or no attention is paid to the need that will arise some time or the Other. More

often than not, the maintenance man begins his on-the-job training with a crisis already at hand. Thus,

the more advanced the technology, the more difficult does skill acquisition- become for me

Age of Plant

An important criterion of maintenance planning to be kept in mind is the age of the machinery in use.

As ageing occurs, the need for maintenance increases quantum-wise. This is a factor that needs

particular attention in India, for here one invariably continues to use machinery and plant way

beyond their optimum economic life span. For example, the average age of plants in India is 22

years, whereas it is just 1 \ years in Japan. With such extensive use, it is obvious that the probability

of failure increases. This trend needs to be carefully evaluated and watched, because it per force

lowers the level of reliability. And because of this, certain machines from the merely essential

category may be included in the *vital*/*critical category. With ageing and consequent vulnerability,

these machines need to be continually monitored and evaluated, so that actions may be initiated

accordingly without bringing on a crisis through breakdown. This can result in an increase of

condition monitoring effort and perhaps also need preventive maintenance checks. An increase in the

frequency of inspection and the cycle of planned maintenance will also perhaps have to be taken

into account. A closely linked problem to this will be the non-availability of spare parts in this

extended life period. No wonder Indian maintenance engineers become so good at improvisation

and substitution.

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maintenance personnel. The different phases in a machine's life can be easily illustrated and

understood from Fig. 5.1. And from it one can easily deduce the different types of skills that the

maintenance department will have to acquire in order to keep the machine operating at an even pace.

From the curve given in Fig. 5.1 we see that the. initial phase can be termed as the infant mortality

stage, where numerous teething problems arise which need to be identified and rooted out with the

help of the collaborators/technical assistance teams, who should be normally available under the

warranty.

Then there is a stable period when normal day-to-day upkeep is all that the machine will require.

Thereafter, comes the phase of *old age' problems, where special skills are needed to keep the 'old

horse' going apace. Obviously, maintenance has a serious responsibility at hand from this stage

onwards, because It is up to them to acquire, develop and refine skills to keep production going at

economically viable levels. Hence, skill up gradation must run parallel to

Time

Fig. 5.1 Bath tub curve.

machinery acquisition, and this up gradation can only be acquired through the adoption of a judicious

programme of training, which must begin well before the

acquisition of the plant.

However well planned the training programme may be, there will be a period in the early stages where the

confidence levels will still be required. Till such time as adequate progress is made and key personnel have

acquired necessary skill levels, the equipment will have to be classified under the critical/vital category.

The answer to all these initial problems lies in having proper technical collaboration/assistance, tie-ups

with the original equipment manufacturer (OEM). Their trained personnel should be available in the

country of installation in the initial phase of equipment's utilisation. And the added advantage accruing

from it would be the on the job training possibilities that this situation would provide.

Maintenance Support Facilities and Infrastructure

The creation of support facilities and an infrastructure to cater to the demands of the entire range of

maintenance activities is not only very expensive but also time consuming. It is also quite likely that

the creation of an expensive facility may not be cost effective, for once created it often transpires that

the demands placed on it may not even be sufficient to justify even its existence. Yet certain specific

facilities to repair, rectify, test or calibrate, are absolutely essential, even though their cost or some

other reason, like lack of adequate and appropriate skills put them out of reach of the concerned

production unit. In such circumstances, facilities such as these will all fall into the "critical" category.

For one has to either provide for *standbys\ or have a sizeable number of 'float* available to tide over

crises, or create clubbing facilities where both cost and competence can be shared and alongside with

this one should have provision (where unavoidable) to send specific items abroad for repairs, tests, or

rate

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calibrations. It goes without saying that all these methods are very expensive in terms of both money

and time. As such the planners must evaluate all the pros and cons with the greatest of care and then

arrive at what should be the most cost-effective solution.

User Skill, Operating Environment, Condition of Usage and Severity of utilisation

The user skill, operating environment, conditions of usage and the severity of utilisation are the factors

that either individually or collectively have a direct impact cn the life of equipment and machinery and

its performance. Any one of these aspects could create a criticality situation demanding special or

critical attention from maintenance. The factors that can lead to this state of criticality need to be

looked into with care. They are, operating speed, temperature, load, vibration, pressures, and factors

such as dust and corrosion. It is a well-known fact that if load is doubled, then wear and tear increases

ten times. And intermittent load, dust and vibration can cut life expectancy down to one-third of what it

ought to be. It is possible that overloading cannot be eliminated fully. Therefore, It is essential that the

operators be trained properly and be made fully aware of the detrimental effects of overburdening a

machine so that they Endeavour to keep it to the minimum. The brunt of all these pernicious factors

has to be borne by maintenance and, therefore, care has to be taken in maintenance planning, of a

number of things like schedules, the frequency at which maintenance work will be undertaken, the

quality of the spares to be used, the methods and periodicity of inspection, condition monitoring, a

watch on environmental assailants like dust and moisture, and warning systems to alert one of the

highly injurious overload situations.

So far, we have been discussing various criteria that can be used for criticality determination.

Let us now examine how criticality can be quantified in terms of maintenance costs, so that

maintenance system designs can be charted, keeping in mind this significant and vital aspect clearly

and without any ambiguity.

Let us take, for example, a list of 100 items in a very large organisation, which have been scrutinized

closely and looked into with care, in terms of cost. And the scrutiny reveals that there are just a few

items which have taken major share out of the entire annual maintenance costs. Now coming back to

these 100 hypothetical items, one can begin with tabulating them, numbering them serially, then

identifying them by their machine identification or machine code numbers, thereafter, the annual

maintenance cost in Rupees which have been incurred on each of these heads should be placed

alongside, and then converted into percentage cost in terms of annual maintenance; cumulative cost

per cent; and percentage of cumulative number of items. In Table 5.1, the items have been tabulated in

the descending order of the annual maintenance cost.

it will be seen that only six out of the entire 100 items account for 80 per cent of the annual

maintenance cost which is indeed very high. Therefore, if cost were to be the only criterion, then these

six items would logically deserve the maximum of maintenance attention and care. If maintenance

information is computerised, and failing that, well documented, then this kind of information retrieval

should be simple and quick and would be of immense help in criticality determination.

However, we are well aware that there are many other factors that affect criticality, which are

specific to type of the problems of a particular plant, industry, or installation. There is a need to

separate the essentials from the nonessentials among the varieties of machines, items, spares and

raw materials that are being dealt with, by maintenance department. A simple way to do so would be

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to code each item by criticality, and this coding could be added to the material or spare part code to

help in easy identification and sorting out by a computer.

1. Most critical production equipment, that is, equipment which has no standby.

2. Critical production equipment with standby.

3. Non-critical equipment

4. Vital—critical equipment, which on breakdown will cause loss in production %

5. Essential—semi-critical equipment, which on breakdown may result in loss of production, but

where invariably production loss can be recovered or made up.

6. Normal—non-critical equipment which on breakdown does not affect production.

7. Purchase value—an equipment bought at a cost of Rs. 10 lakhs should obviously be given

greater maintenance attention than an

equipment bought for only Rs. 10,000.

8. Functional value—i f vital equipment essential for production becomes unserviceable, then it

will result in direct loss of production; hence such equipment must receive greater maintenance

attention.

9. Attention value—equipment that frequently breakdowns or is prone to breakdowns should

receive adequate maintenance attention.

MAINTENANCE SYSTEM DESIGN OPTIMIZATION While carrying out a detailed criticality analysis, the following factors should be taken into account:

1. Down time cost

2. Relevance to direct production efforts

3. Standby availability

4. Intensity of demand of that service, i.e. severity

5. Downstream effects

6. Dangers to safety to life and property

7. Skill availability

8. Spares availability.

If. may be remembered that maintenance system design is not dependent alone, but on certain other

factors as well. These factors are:

(a) Age of plants

(b) More variety of equipment (e.g. different countries of origin)

(c) Replacement costs

(d) External and internal maintenance support facilities and infrastructure.

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Low Breakdown maintenance

Maintenance system design optimisation is not a static concept but a dynamic one and it changes

as time goes by. A method that can be suggested is to design a matrix, assign weight age and thus get

criticality indices for various equipment in the organisation. By superimposing the OEM's

recommendations on these, one can add a reliability analysis on to it as well. Thereafter a validity test

will also be required to be done to complete the exercise. After having done this, the entire plant,

equipment and machinery can be divided into four types or categories:

(a) Vital

(b) Essential

(c) Important

(d) Normal.

This is known as the VEIN analysis. Having done the analysis, a curve of criticality can be plotted

on the Y-axis, and the type of maintenance on the X-axis (see Fig. 5.2). Basically one has to distribute

the equipment into a mix of

Type of maintenance

Fig. 5.2 VEIN analysis

Breakdown and planned maintenance (PM). The planned maintenance-can

be further subdivided into planned, preventive and predictive maintenance depending upon the

equipment, its criticality, complexity and its need and cost.

by looking at the allocated VEIN analysis chart, it will be noted that the vital equipment will have a

small percentage of breakdown maintenance (BM), breakdown can never be eliminated, but, a very

high share of PM. Then the essential category of equipment will have slightly larger share of BM and a

huge percentage of PM. Finally , the normal equipment will perhaps suffice by only having breakdown

maintenance. This kind of a mix will have to be decided upon because the direct cost of PM is high, but

the consequential cost at MM is also high. A picture will emerge which will provide the organisation

with a proper mix of breakdown maintenance and planned maintenance which mainly a mix of planned,

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preventive and predictive maintenance systems, as required by respective plant, machine and

equipment. This will be providing savings in PM costs were not necessary and give the plant high

serviceability and availability. This has to be continuously updated with the feedback received along

with the defect analysis and the down time analysis reports.

The work force requirement for breakdown and preventive maintenance is shown in Fig. 5.3.

M a

n power needed vs. Stable BM and PM mix

fig. 5.3 Workforce requirement for breakdown and preventive maintenance.

The basic manpower needed for operating on a stable equipment is shown M h stable BM and PM

mix (see Fig. 5.3). Added to this will be the cushion to Hike care of the peaks. This is the level at which'

manpower needs have to be fixed.

,OT

Contract

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MAINTENANCE AND REPAIR Types of Maintenance

Maintenance planning

Maintenance of Construction Equipments

Equipment maintenance and Repair workshop layout

Sections of workshop

Equipment maintenance and Repair records

Spare part management

Objectives of Maintenance

• To maximize availability of machinery and facilities needed for smooth production.

• To minimize downtime due to breakdown of machinery.

• To ensure long life of machinery.

• To avoid high rate of depreciation of capital.

Breakdown Maintenance

Breakdown of machine can occur due to following reasons

• Incorrect operations, Inadequate servicing, Lack of inspection.

• Due to unpredictable accidents which causes failure of machine

• Due to gradual wear and tear of parts

This maintenance is much more expensive as compared to preventive maintenance due to

• Increase in depreciation cost

• Payment to idle operator

• Overtime to maintenance staff to do emergency repair.

• Idling of matching equipment

Preventive Maintenance Objectives of preventive maintenance

1. To ensure breakdown free operation and optimum life of equipment.

2. To reduce cost by reducing downtime of equipment.

3. To keep the machine in proper condition so as to maintain the quality of product.

4. To ensure the safety during the work.

5. To keep the plant or machinery at the maximum production efficiency.

Functions or Elements of Preventive Maintenance

• Inspection or Check Ups

• Servicing

• Planning and Scheduling

• Record and analysis

• Training of maintenance staff

• Storage of spare parts

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Advantages of Preventive maintenance

• Reduction in production downtime

• Lesser overtime payment for maintenance staff.

• Lesser number of standby equipments

• Less expenditure on repair

• Lesser spare parts needed to remain in store

• Safe operation of equipments

Requirements of good preventive maintenance

• Good supervision and administration of maintenance department

• Correct, clear and detailed instructions be given to the maintenance crew and to the operators

• Operators should be well trained

• A good lubrication programme should be chalked out

• Proper maintenance record should be maintained

• Adequate stock of repair should always be kept.

• All repair tools must be available

• Proper coordination between maintenance, planning and purchase department.

• Standardization on types of equipments deployed to control inventory and to have

specialization.

• Use of mobile service vans

• Establishment of well equipped service and repair workshop

• Before transportation of equipment from one project to another service or repair it and then

transport.

Phases of Maintenance Planning

• Anticipation of maintenance work- Instructions of manufacturer of machine, Talking to operation

staff, doing inspection, and by seeing behavior of machine during operation.

• Preparation of maintenance schedule

• Manpower planning- Involves Analysis of manpower requirement, Manpower availability,

identifying training needs and arranges training.

Complexity of job, Periodicity of activities and time required to each activity, Quantum and type of

work, Layout and location of equipment, Allowances for leave, Holidays, Shifts etc. are considered for

deciding manpower requirement.

• Development of maintenance information system

• Follow up and check up

• Evaluation of work- Maintenance cost in a year, Ratio of downtime with available hours,

Frequency of breakdown, Break up for downtime, for poor maintenance, bad operation and bad

design.

• Anticipation of maintenance work- Instructions of manufacturer of machine, Talking to

operation staff, doing inspection, and by seeing behavior of machine during operation.

• Preparation of maintenance schedule

• Manpower planning- Involves Analysis of manpower requirement, Manpower availability,

identifying training needs and arranges training.

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Maintenance of Equipment

Inspection

• Inspection helps in detection of faults, which can be rectified in time, and costly breakdowns can

be avoided.

• Inspection crew must work independently of the operational and field repair staff so that

unbiased check can be exercised on the equipment.

• Calendar for inspection should be prepared with a checklist of the items to be inspected.

• Frequency of inspection should be carefully decided.

• Nature of equipment, its importance in production, Time interval between first indication of

trouble and actual failure, Age of the equipment, operating environment are considered while

deciding frequency of inspection.

• In case of external inspection defects are identified by checking engine sound, color of exhaust,

oil pressure, oil and water temperature etc.

• Internal inspections includes nut and bolts, tyre pressure, amount of wear on common parts,

brake linings, engine parts, batteries, fuel supply, cooling fans, wire roes etc.

Servicing • Mechanical components of machine give good performance for longer periods when they are

systematically serviced as per manufacturer.

• Servicing can be done by two options- Mobile servicing van or Central servicing depot. It is

worthwhile dividing the maintenance personnel into specialized teams each attending to one

particular part of machine.

• Maintenance supervisor should prepare a check list of various parts and devices to be checked

by servicing screw during servicing.

• Storage of fuels and lubricants should be done in central depot.

• Proper lubrication of machines is a vital aspect of servicing.

• Storage of fuels and lubricants should be done in central depot.

• Another item during servicing is supply of cooling water. Clean and soft water should be used.

Crew should check entire cooling system and make adjustment wherever necessary.

• Servicing of wheels and tracks is another major item of maintenance.

• Other items to be attended include electrical parts, wire ropes, cutting blades, power control

units, clutch and transmission.

Inspection Servicing Repairs

Aspects of Maintenance of Construction Equipment

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Field repair facilities • Static field maintenance workshop should be provided on site at suitable location to cater day to

day needs of entire fleet of equipments.

• It must be divided in two parts one for repair work and other for storage of various parts.

• The workshop floor should be preferably being of concrete and the workshop should be supplied

with electric power, water and compressed air.

• Tools provided in the workshop are

1. Benches, vices, cupboards, racks

2. Portable electric drills, grinders, jacks, crowbars

3. Lifting tackle, gantry or mobile crane.

4. Portable welding equipment, oxyacetylene cutting.

Repair workshop

Field repair workshop can be established at a major project site under the following conditions

• Long project duration generally exceeding 3 to 5years.

• Equipment usages in the project are very high.

• Non availability of adequate local repair facilities in the nearby vicinities.

• Non availability of adequate spare parts from local markets.

• Project located in remote and difficult terrains such as mountainous snow, desert areas.

• Heavy repair and maintenance commitments due to round the clock work scheduling

Sections of workshop

• Workshop office

• Receipt and Inspection Section

• Store Section

• Repair Section

• Ancillary Section- blacksmith, tinsmith, welder, carpenter, machine shop, painting, electrical

battery charging.

Equipment maintenance and Repair records

The main aim of record keeping is to provide appropriate information about

• Per unit output cost of each equipment

• Economic life of equipment

• Fuel cost

• Cost of spares

• Operation and Maintenance cost

• Planning of spares

• Percentage utilization of equipment on a particular job

Equipment Records

• Daily Working data

• Monthly Working data

• Log Book- Operators record, fuel consumed, period of breakdown and it causes, period of

idleness and its causes, operating and maintenance instructions.

• History Book

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Spare part management • In the context of construction equipment maintenance, spare part management means accurate

listing of spares available in order to ensure that they will be readily available if the situation

demands. The main objectives of spare part management are

1. Maximizing equipment availability

2. Reduce spare part inventory level

3. Reduce operating cost

4. Achieve unstoppable production from equipment

• It includes periodical analyzing spare part stock level, processing requisition, maintaining the

stocks in store.

• Spare parts of equipments are basically divided in three types Consumable, Fast moving, and

slow moving.

• As items in case of spares of equipments are large in number their proper stocking is necessary

so that individual items can be easily. Standards items should accessible are stocked at one

place and non standard items for each equipment should be stocked separately. Over stocking

of spare should be avoided.

• Over stocking of spare parts may result from several causes such as

1. The fear of scarcity or Non availability when needed prompts the project authorities to buy large

quantities of spare parts, especially in case of imported equipment

2. Collection of different make and models of equipment on the project

3. Some of the manufacturers, at the time of offering the equipment give list of spares with quantity

to be purchased with the equipment. Further suppliers will insist on buyers to purchase large

quantities of spares to escape the effects of obsolescence.

4. Improper plant/equipment planning

5. Acquisition of old machines together with their spare parts often result in substantial portion of

spare parts remain unutilized.

6. Codification to the various parts or items in spare is important. Codification will be useful in

identifying the part in spares. The codes used for this purpose may be numerical, alphabets or

both.

7. Standardization will be helpful in reducing the inventory cost.

8. The main objective of spare part management is to keep inventory cost as low as possible by

keeping items in the store for various equipments. Inventory model of operation research can be

effectively used for this purpose. By using this it is possible to determine procurement level,

procurement quantity and frequency of procurement. The most famous model can be used in

this case will be ABC analysis.

The most important question while deciding about the inspection is that which machine should be

inspected and when, for one cannot inspect all machines every day. Hence, criticality analysis would

be required to arrive at a decision. Such an analysis would include the following questions about the

machine:

(a) Will its failure hold up the production?

(b) Will its failure be a threat to the health and safety of the worker?

(c) Will its stoppage cause wastage of material being processed?

(d) Will it cause damage or danger to other equipment?

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INSPECTION CHECKLIST Take, for example, the case of a fan or a pump which has been considered critical and will be

inspected daily. The inspection routine would involve carrying out checks for

(a) any abnormal vibrations, or any abnormal noise;

(b) the temperatures of all the bearings to ascertain that they are at acceptable

levels and that they are not at overheating levels;

(c) leakages from the glands and gauge to see whether they are excessive;

(d) oil levels in cups; and

(e) Grease nipples to ensure that they are not dry.

This is a simple example of an inspection checklist, which indicates exactly what to look for and do.

Similarly, a daily checklist for a capstan lathe gear box would include:

(a) Physical inspection of gears for teeth condition and smoothness of meshing

(b) Check for noise and vibration

(c) Check for oil leakage or seepage

(d) Check for any visible cracks or dents on the box.

FREQUENCY OF INSPECTION

The frequency of inspection is determined by an engineering analysis, which considers the

following parameters:

(a) Age of the machine, its condition and value.

(b) Severity and intensity of service.

(c) Hours of utilisation—are they prolonged—or intermittent (for 8, 16 or 24 hours a day)?

(d) Susceptibility to wear and tear—is the machine subjected to dirt, friction, fatigue, stress,

corrosion, smoke, ash?

(e) Susceptibility to damage—is the machine subjected to severe vibration, overloading,

abuse, heat, freezing cold?

(f) Susceptibility to losing adjustment during use—will the maladjustment or non-alignment

affect the accuracy or functioning? Will the lack of proper balancing affect performance?

(g) Safety requirements and considerations.

(h) Criticality of item—If very critical, then the item may need daily inspection.

As time goes by, the deciding parameters may undergo change and then the frequency will need

to be changed as per one's experience.

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LUBRICATION Lubrication plays a very important and effective role in planned or preventive maintenance and rightly,

therefore, it is basic to maintenance planning. Ensuring proper lubrication can and does reduce a large

number of breakdowns. More so, in those industries where machine or equipment is exposed to an

abrasive or corrosive environment. The role of lubrication where machinery is exposed to the ravages

of dust and grime, or to moisture and salt laden* sea-breezes, or the punishment inflicted upon

machinery and plant in the chemical industry as a whole cannot be overemphasized.

Proper lubrication helps to (a) prevent rust formation; (b) reduce friction, thus reducing wear,

scoring and seizures, and economizes on power consumption; (c) reduce heat; (d) wash away worn

material and particles; (e) increase equipment life.

The points/places that need lubrication, the quantity to be used, the type of lubricant, and the

required frequency should normally be indicated by the original equipment manufacturers in their

operating and maintenance manuals. However, at times, it is seen that such information is either

insufficient or not complete and comprehensive. The OEM should alto indicate the substitute

lubricants, oils and greases. The design of the equipment must provide easy access and the means of

lubrication; if not, lubrication piping or channels, which eventually terminate in oil cups, or grease

nipples must be provided with maximum and minimum marks indicated to ease the lubrication.

Sometimes it is preferable to seek help of the oil companies who will provide help, if asked for, in the

hope that the organisation will buy their lubricants sooner or later. They have a special advantage, for

they can apply knowledge gained from the problems and experiences of their many users, to the

specific problems of the concerned organisation. Another valuable and helpful source is the first-hand

experience gained by other users Working under similar conditions or by the personnel of their own

organisations.

The quality and quantity of lubricant used have an important bearing on any lubrication

programme. Lubricant properties have to be carefully selected to meet specific needs of the

machine and its operating conditions. For example, the use of very little amount of lubricant is

worse than its excess use. However, excess too can cause problems such as overheating and

churning. Hence, the amount of lubricant needed is an important criterion. It can range from total

immersion in an oil bath to a few drops only.

Lubrication Programme

Proper lubrication requires a sound technical design for lubrication and a set of proper

management and control systems to ensure that every item is properly lubricated. The following

steps are recommended in developing a lubrication programme

1. Identify and list every item/equipment that needs lubrication. It can be

form of a register, punch-card or tape.

2. Provide identification number/code for every equipment so that it can be recognised and

cross-referred to in the register or punch-card, including its location in the factory.

3. Designate every part, point, or location on each of the above equipment, which needs to be

lubricated.

4. Earmark the lubricant to be used for each of the locations/parts by either type or code or as

per lubricant manufacturer's code, and indicate substitute lubricant

5. Lay down the correct method of lubrication to be followed.

6. Establish the frequency or periodicity of lubrication.

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7. Identify those equipment that can be lubricated while in operation and those for which a

shut-down is mandatory. Use colour codes for such . identification and these should be

prominently displayed on the machine itself.

8. Decide who are the persons responsible (by names preferably) for lubrication.

9. Lay down lubrication routes by oilers.

10. Standardise lubrication methods and lubricants to be used to as small a number as

possible.

11. Create proper storage and handling facilities for lubricants, and lay down procedures for

lubrication to help in safety and to avoid spillage and waste.

12. Take recommendations of lubricant manufacturers seriously and evaluate the newer

lubricants proposed, to take the best advantage of the latest developments.

13. Analyse the failures due to too much, too little or no lubrication, and take immediate

corrective actions to avoid their recurrence.

Planning

The following planning effort can help in formulating a well-thought out lubrication plan:

( I ) Survey. In establishing a lubrication plan, the first step is to carry out a survey of the

plant/equipment/machine to determine the type of lubricant required and the frequency of lubrication.

Here the help of oil companies can be made use of; they will be able to provide information about the

correct type of lubricants to be used, and the frequency of application. They can also help in the

standardisation of use and thus bring about a reduction in the number of lubricants, after the

completion of the survey. Needless to*say, the fullest of cooperation •must be extended to them by the

maintenance and the operating personnel.

(ii) Lubricant requirement. It will be known after the survey has been made is to which

lubricants are required. Then a comparison has to be made between the lubricants that are in use and

those which have been recommended by the manufacturers. The next step will be to rationalise the

requirements by inducing the variety of lubricants after due consideration of suitability and compatibility

of the alternative brands/types available in the market.

( i i i ) Lubrication system. Develop lubrication charts for each equipment, clearly showing all the

lubrication points, the types of lubricants required, the method of lubrication, the quantities, and the

frequency. These charts can be affixed on the equipment itself for easy reference. Use a colour

scheme or colour rode to indicate each spot that needs lubrication. Have a distinguishing code to

yearly indicate the spots to be lubricated by the operator of the machine and by the maintenance

personnel.

(iv) Schedule. Having determined the lubricant to be used and the correct frequency, it is

necessary to lay down a schedule of operations. This can be done by having check sheets made for

daily, weekly, and monthly work-loads. This check sheet can use standard time or expected time to

indicate the time required for lubrication. It must consolidate all information, like parts to be lubricated,

type of lubricant to be used, the amount and method of lubrication, and so on.

( v ) Training. Proper training is the key to success in this field as elsewhere.

It should be ensured that each operator and maintenance man is properly trained to do his specified

task. He must know and recognise the system of colour or coding used to distinguish and differentiate

types of oils, and grease the points to be oiled/greased, the method of lubrication and the exact

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quantity to be put in and the frequency. A lubrication manual prepared by the Maintenance Manager,

indicating the full details will go a long way in helping personnel to do their jobs properly. The oiler must

be literate, intelligent, trained and capable of proper work to ensure success.

(vi) Storage/Handling. This is of great importance. Keep sealed oil and grease drums under

cover in a dry place and observe laid down safety and fire precautions. Transfer of oil from drums to

cans, etc. should be done under supervision and clean conditions, using strainers if needed. All

lubrication appliances and handling equipment must be kept very clean to prevent contamination or

ingression of moisture or of foreign matter.

TABLE SHOWING COMPUTATION OF LUBRICANT

Lubricants List of Vehicles at construction site

1 Tata station 1

wagon (LMV)

DCM 1 Toyota

(CV)

Shockley land

09V)

Name of company

supplying oil

Brand Grade Total

Nos of vehicle at site 20 10 5

a) ENGINE OIL 4 Litre/ea 6 10 CASTROL GTD 15W/40 80+60+50=190

LITRES

b) Brake Fluid (L5 litre/ea 1 2 HPCL Super duty

Brake fluid

DOT-3

10+10+10=30 LITRES

c) Transmission oil 3S Litre/ea 5 8 HPCL Gear oil EP 80 70+50+40=

160L1TRES

1.5 litre/ea 3 5 CASTROL Trans power TQ 30+10+25=65 LITRES

e) Differential oil 1 litre/ea 2 4 ANCHEMCO Terrostat 88590 20+20+20= 60 LITRES

0 Coolant 6 litre/ea 10 20 SUNSTAR GOLDEN

CRUISE

1400M

120+100+100 = 320

LITRES

g) Wheel hub grease 0.1 kg/ea 0.25 1.0 CASTROL Castrol grease

AP2

2+2.5+5=9.5 LITRES

Documentation of maintenance data and evaluation of maintenance performance.

The proper documentation of maintenance data should be maintained machine wise regarding:

a. Types. of break downs and frequency of occurrence

b. Parts replaced and period of service

c. Planned periodic inspection dates

d. Cost of maintenance of the machine

e. Display of maintenance charts, Schedules, aids

7.1.0 The function of maintenance department is to take corrective

action if its performance is not up>to desired level. The performance can be

quantified by use of maintenance indices, some of them are:

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a. Percentage machine down time :

Machine hours lost due to maintenance X 100

Total calendar hours during that period

b. Percentage maintenance cost :

Total expenditure in maintenance x 100

Total value of output

c. Percentage utilisation :

Total hours worked

------------------------------------------------------------- X X100

Total hours available during that period

D . Inventory Index: Cost of maintenance spares used

Total cost of maintenance spare stock in hand

8.0 Modern Maintenance Techniques

The oil and wear analysis (OWA) method is used to detect excessive wear of lubricated

parts inside the machine that may lead to critical machine trouble. The presence of metal

particles from worn-out parts in the lubricated oil indicates the level of wear of components

inside the machine. When the wear of some components is high then the amount of metal

particles in the oil will be excessive and this abnormal condition warrants, timely

replacement of worn-out parts. Centralised lubricating points have been developed in

modern machines for easy lubrication of inaccessible parts. Electronic sensing devices are

fitted on major assemblies such as engine, gear box, transmission system to give the

operator early warning of any abnormal wear in the systems.

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SITE WORKSHOP LAYOUT AND ORGANISATION ( Workshop)

INTRODUCTION

All construction companies provide workshop facilities for inspection, maintenance and repair of

equipment. These workshops are designed to meet the requirement of

Inspection/Maintenance/Repair of equipments. The workshops are designed in 3-Tier system

(i.e.)Light repairs (Type A), Field repairs (Type B) and Base repairs (Type C).

Light Repair workshop

The light repair workshops (Type A) are located in temporary accommodation or on wheels at the

Project Site. These workshops carry out inspection, servicing and light repairs to equipment'*'. Fast

moving spares for light repairs and few minor assemblies are stocked in these workshops. The

technical manpower is normally trained in multi trades so that they can handle two or three repair

systems/trades. The type of plant and machinery for the workshop will depend upon the number/type

of equipment in use at the project site and duration of the project. The light repair workshop normally

consist of the following Trailer mounted Equipments/Tools.

1. Generating Set 5-10 KVA for Power Supply

2. Workshop Machinery - Lathe, Drilling Machine and Grinder

3. Electric Welding Generator/ Transformer

4. Gas Welding Sets

5. Servicing Trailer - Diesel/Electric driven compressor, pneumatic

6. hose, H.P., L.P., Pumps for grease, oil and water pump for washing vehicles.

7. Tradesmen Tools - Blacksmith, welder, Tinsmith, Electrician, Electrician,

8. Vehicle Mechanic (Auto / Diesel), Turner, Carpenter, Maintenance Tools, Special Tools.

9. Jib Crane - Tools and Tackles

10. Store Bins

11. Recovery Vehicle

Light repair workshop back loads vehicle/equipment requiring heavier repairs to field repair

workshops.

Field repair workshop

The field repair workshops (Type B) are normally located in zonal areas of the company giving

repair/maintenance cover to 3 or 4 projects. These workshops are normally semi-state with full range

of repair/maintenance equipments. The workshop stocks adequate spares/assemblies for

replenishing the light repair workshops. The workshop undertakes the following:

1. takes over the overload of light repair workshops

2. carry out heavier repairs - such as overhauling engines, gear boxes, transmission, hydraulic

systems etc.

3. Restricted repairs to accident vehicles Local purchase of spares and local contract repairs to

vehicles/ equipment.

4. Recovery cover to project vehicles

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5. Sends special teams with major assemblies to project site to carry out major repairs in situ.

6. Reclamation/Repair of minor assemblies received from light repair workshops.

7. Inspection/Down gradation of vehicles

8. Carry out specific fuel consumption tests and target Km. per litre tests on vehicles.

9. Carry out any modifications to vehicles/equipment as directed by Base workshop.

10. Evacuation of vehicles/equipment to base repair workshops.

Field repair workshop can also be established at a major project site under the following conditions:

1. Duration of Project exceeds 3 to 5 years

2. Project has several types/number of equipments

3. Local repair facilities from nearby to:vn are not adequate

4. Spare parts are not readily available from local market

5. In-accessible areas or lengthy lines of communication-Mountainous

snow, desert areas.

6. Heavy repair/maintenance commitments due to three shift working.

Workshop officer is responsible for the following functions:

1. Administrative/Technical control of all departments in the workshop.

2. Preparation of Annual Inspection/ Maintenance Programme for Equipment.

3. Provision of spares/assemblies for repair.

4. Timely repairs to the equipment in workshop.

5. Maintenance of records for equipments.

6. Budgetary contract repairs and local purchase of spares.

7. Local contract repairs and local purchase of spares.

8. Carry out any major design modification to equipments.

9. Audit on the quality of repairs, inspection done by workshop personnel.

10. Stock checks on stores. ,

11. Security and fire precaution.

12. Approve back-loading of equipment to base repair workshops.

Security and fire fighting section

The security personnel are responsible for the security of the personnel, stores equipment and records

of the workshop. They should also check for any industrial espionage by the competitors. The fire

fighting personnel will take all necessary fire prevention precautions and hold fire-fighting practices

regularly to educate the personnel. Maintain fire-fighting equipment regularly.

Workshop Office

The Office Staff work directly under the workshop officer. They are responsible to maintain all

vehicle/equipment records. Prepare annual inspection/maintenance programmes and ensure

the programmes are implemented.

R & I Section ( Receipt and Inspection)

The receipt and inspection section is responsible to acknowledge receipt of the work order from

user for repair of equipment. The inspection section will carry out in/out inspection of equipment.

The receipt section prepares repair cards for equipment and makes necessary entries in Log

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Books/History Cards after repairs. A specimen repair card and log book is shown in Appendix D,E.

The inspection section controls the use of Recovery Vehicle and servicing equipments.

Stores Section

The stores in-charge is responsible for the following:

1. Planning and procurement of spares;

2. receipt. Inspection and Storage of Spares:

3. Preservation of stores as per the guidelines indicated in Appendix

F.

4. Issue, accounting and stocktaking of spares.

5. Regularisation of losses in stores due to pilferage, deterioration.

6. Regular turnover of spares.

7. Maintain stores ledgers.

8. Issue of special tools and expendable stores to shops.

9. Costing records.

10. Back loading of surplus stores, scrap etc.

11. Procurement of Miscellaneous stores and accounting.

12. Safety of stores.

Heavy Repair Section

The section is responsible to carry out repairs/modifications to Heavy Equipments such as

Earthmoving Machines, cranes and Heavy Misc. Equipment. The engine overhauling section will carry

out the overhauling of vehicle/equipment engines.

Vehicle Repair Section

The section is responsible to carry out repairs/modifications to vehicles, trailers, and motor- cycles

generating sets, small construction equipments and small misc. equipments.

Ancillary Section

The ancillary section has various shops such as blacksmith. Tinsmith, welder, carpenter, upholster,

painter, machine shop, minor assembly, electrical, battery charging, fuel injection equipment,

instruments and telecommunication repair shops. These shops will assist heavy equipment, vehicle

repair sections in carrying out repairs to equipment.

Workshop Procedure

The user normally sends the equipments for repairs/maintenance to the workshops with a work order

indicating likely defects in the equipment. The R & I Section acknowledges the work order and the

Inspection section carry out a thorough inspection of the defective equipment. Detailed list of defects

are mentioned by the inspection section. The R & I section prepares a repair card listing all defects in

the equipment. The defective equipment is moved to respective repair bays where it will be attended

by mechanics under the supervision of shop foreman. The spares required for repair are drawn from

the stores and old spares returned to stores.

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I. The shop foreman carries out a preliminary test on the repaired equipment and then sends the

equipment to the inspection team in R & I section for final testing.

The R & I team finally carries out the inspection of the equipment and endorses fitness certificate

on the repair card.

ii. The R & I section closes the repair card after final tests and records all repairs carried out and

spares fitted in the log book of the equipment. In case of major repairs beyond the scope of

field ‗repair workshop the equipment is sent to the base workshop by the r inspection team after

the approval of the workshop officer.

The final classification of equipments based on usage and major repairs is also determined by

the inspection team.

Regular inspection of construction equipment is an important factor to keep the equipment in

serviceable condition at all times. Such inspection enables timely detection on faults which can be

rectified in time and costly breakdowns are avoided. The inspection should be done at regular intervals

by qualified personnel. The Annual Inspection Programmes for equipment are prepared in consultation

with users and Workshop Officer. The inspection team should work independently so that unbiased

check can be exercised. The inspection staff should be technically qualified and competent for the job.

The inspection department decides the classification of equipment based on usage and major repairs

carried out on the equipment. A specimen inspection form for earthmoving machines is given at

Appendix G. Similar inspection forms can be developed for different types of equipment.

Base Repair Workshop

Base repair workshop (Type-C) is a static workshop and normally located near the Head Office of

the Company. The Chief Mechanical Engineer at H. 0. controls the policy on overhauling of

equipments and procurement of new equipments in consultation with the management. These

workshops are fully equipped with plant and machinery.

Base repair workshops undertake major repairs beyond the scope of field repair workshops and

also complete overhauling of vehicle/equipment. These workshops also carry out the following:

1. Train mechanics and operators.

2. Trade testing and up gradation of mechanics/operators.

3. Major modifications to equipments.

4. Manufacture of special attachments to equipments.

5. Trail assembly of production plants such as batching plants, cable ways, crushing plants,

refrigeration and ice plants, heavy earthmoving machinery, tunnel boring machine, piling

equipment etc. Send specialists to site to erect the equipments mentioned at Para (e) above.

6. Maintain records of all equipments held by the company and update them based on data

recorded by Field Workshops/Users,

7. Maintain adequate stocks of spare parts.

8. Prepare scale of spares required for stocking in light, field repair workshops.

9. Advise Light, Field Repairs Workshops on Preservation of Stores.

10. Testing of new equipments procured by the company for projects.

11. Procurement of new equipments for workshops.

12. Decides overall policy for inspection/maintenance of equipments.

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13. Transfer of equipments between projects and arranging rolling stock/road transport.

14. Arrange imported spares.

15. Disposal/auction of old unserviceable equipments, spares and workshop

scrap.

USE RATE / HIRE CHARGES Construction companies who are undertaking major projects engage capital Machinery for

construction. The construction equipment constitutes about 15 to 20 percent of the Project cost in a

reasonably mechanized construction works. Mechanisation in construction of infrastructure projects

like High way roads and irrigation works has many advantages. The consumption of regular

consumables like fuel and lubricants and consumable spares constitute about 25 to 30% of the capital

expenditure. Hence if a Project is about 100 crore, the capital machineries would be around 15 to 18

crore and the spares and fuel oil and lubricant would be around 4 to 5 crore. Hence notionally

construction company tends to charge about 4% of the equipment cost as Hire charges when they

assign equipment for a Project. This is a composite figure and is broken as 2.5% as charges for

equipment hiring on monthly basis. The project is expected to bear about 1.5 % additional charge over

the Hiring charges on the equipment to cover for Maintenance and repairs.

The policy with regards to Hire charges vary from company to company. A company may own an

equipment and may compute the Owning and Operating cost of equipment and may cost this to the

projects it is executing based on the Owning and Operating cost.

In another model a company may create another company to procure and own the equipment in order

to lend this to their subsidiary companies at a given rate. L & T ECC floated LALLCO for dealing with

equipments and they were charging 5% to the projects they had lent.

a) 2.8% of the equipment cost on monthly basis as Hire charges

b) 2.2% was charged to the project for Maintenance and repair works and other overhead

charges.

Of course the above charge had a good profit component. In fact the company showed 25 % profits by

lending the construction equipment on Hire to L & T ECC their subsidiary company.

In the case of Nagarjuna construction company the company charges around 2.5% as Hiring charges

per month on the equipments assigned to the Projects. The equipment is owned by the Company. An

additional 1.5% is charged, which the particular project needs to bear.

The term use rate is applied in the industry to indicate the money value the company charges to the

project based on the use say it could be Rs/ 1200 Hours ( on a yearly basis based on single shift or Rs

/ 120 hours on a monthly basis) A month is considered as 25 days working days.

Hire charges can be based on the policy the company wish to follow . It could be based on Owning and

Operating cost , or it could be based on percentage of capital equipment cost charged for a convenient

usage period say on Monthly basis.

TRANSFER VALUES OF EQUIPMENT:

When the equipment procured for a project has been deployed on the project completely and the

Project has ended before the Useful Economic life of the equipment, the equipment is revalued at the

end of the project. Valuation of Construction equipment is carried out either internally or an external

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registered valuer can be assigned for the job of re-valuation who is a competent person for valuing

Plant and Machinery , a member of the Institution of valuers or a Registered valued under the wealth

tax holding a valid registration under the category ― approved valuer of Plant and Machinery‖.

.

When the equipment is to be transferred to another project ,companies may consider either the Book

value or the re evaluation value this depends upon the policy adopted by the company. Transfer values

are computed based on the Reinstatement value after depreciating the asset for the periods used on

the project. Depreciation can be computed on straight line basis or Diminishing balance methods.

Normally a straight line balance method is adopted. If the equipment involves any repair cost to bring it

to a normal working condition the cost needs to be deducted from the Reinstatement depreciated value

to arrive at the Potential value of the equipment.

Transfer values represents the potential value + any cost on account of dismantling at the user end,

transportation cost, re-installation and commissioning cost of the equipment at the next project site.

One of the important deductions admissible in computing income from business is Depreciation i.e.

Falling value of an asset due to use. (falling in value due to time, due to deterioration, due to wear and

tear, due to corrosion etc. )

Depreciation on building, machinery, plant or furniture

Depreciation - In any business, raw material is used fully and immediately, while plant and machinery

is used slowly over a period of time. After the estimated life of machinery, its value becomes Nil.

Hence, it is fair that cost of machinery is charged over the period of its estimated useful life. This is the

basic principle of depreciation on capital goods. Since land does not depreciate, no depreciation is

allowed on land.

Under Income Tax, depreciation is calculated on the basis of 'block of assets'. 'Block of assets' means

a group of assets falling within a class of assets, in respect of which the same % of depreciation rate

has been prescribed. e.g. all machinery having rate of depreciation as 25% will form one block of

asset, machinery having 40% rate of depreciation will form another 'block of asset' and so on.

Depreciation is allowed on actual cost of the asset. Interest paid on borrowed funds and capitalized as

pre-commencement expenses before the asset is commissioned is added to cost of the asset and

depreciation claimed on such expenditure. Thus, pre-production expenditure can be included in cost of

the machinery and depreciation can be charged on such 'actual cost'.

Depreciation is calculated on Written Down Value (WDV) method. e.g. if cost of machinery is Rs 100

and rate of depreciation is 10%, depreciation in first year will be Rs 10 and written down value (WDV)

of machinery will be Rs 90 (100-10). In next year, depreciation will be 10% of Rs 90 i.e. Rs 9. Next

year, the WDV of machinery will be Rs 81 and depreciation allowed will be Rs 8.10 and so on. If the

asset is put to use for purpose of business for less than 180 days, only 50% of normal depreciation is

permissible. In other words, full depreciation for the year is permissible only if asset is commissioned

before 30th September of that year.

If depreciation cannot be fully claimed in a particular year for want of profits, the un-absorbed

depreciation can be carried forward for any number of succeeding assessment years. [section 32(2)].

[Earlier limit of 8 years removed vide Finance Act, 2001]

The depreciation rates in respect of some important assets are as follows:

1. Residential building – 5%. Others – 10%. Purely temporary structures – 100%.

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2. Furniture and fittings including electrical fittings – 15%

3. Motor cars 20% . Buses, lorries, and taxis used in business of running them on hire – 40%, aero

plane – 40%. Ships – 25%

4. Pollution control equipment and specified energy saving devises - 100%

5. Normal machinery - 25%

6. Computers including software - 60%.

7. Books by professionals – 100% for annual subscription and 60% for others - books in library -

100%.

8. Ships - 25% (25% for vessels used in inland waters).

9. Intangible assets - know-how, patents, copyrights, trademarks, licenses, franchises or any other

right of similar nature - 25%.

ESTIMATING REQUIREMENT OF MACHINERY

Quantum of Work

Time Period for Completion

Output of Equipment

a) Quantum of Work: The total quantum of work involved in each operation such as earthwork,

metaling, surfacing, compaction, etc. May be determined making due allowance for likely

access and wastage. The quality is to be express in units suitable for each item. The

quantities can be taken from Bill of Quantities of the project.

b) Time Period For Completion:

a. Total duration with the date commencement and date of completion of the job needs to

be decided.

b. In arriving at total time period for the completion of the project allowance should be made

for loss of time due to bad weather, change of work site, night work, shift work, on

servicing and inspection of machines periodically, shifting of equipment like Hot-mix plant

and erection etc.. It is a practice in earthmoving operations to assume 50 Mts. per hour

for estimating production.

c. In most parts of India, working season is limited to maximum of 8 months in a year.

Allowing for holidays / off days actual working days may vary from 21 to 25, in a month.

By working one shift of 8 hours annual utilization of equipment may work out to be 1000

hours to 1500 hours. These figures will vary if the climatic and other conditions are more

severe. Annual utilization will also vary with the type of job and the machine involved.

d. After making an assessment of equipment requirements, 10 percent addition should be

provided as standby for unexpected break – downs, unforeseen difficulties, etc… regular

repairs of equipment should however be planned for the rainy season.

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No of Shifts Operations:

Two shift operations are economical and should be employed whenever possible. Three shift working

result in frequent break-downs and low availability, thus necessitating more standbys and increasing

the cost.

Schedule working hours with 200 working days available in a year should be as follows under average

working conditions:

1 - Shift Operation = 1200

2 - Shift Operation = 2000

3 - Shift Operation = 2500

If more or less than 200 working days are available, working hours should be changed proportionately.

For old machines (i.e. after the first overhaul) scheduled working hours should be taken as 80% of the

above figures.

Since the plant planning is don on peak requirements it is worth-while that construction scheduling is

done in such a manner that peak requirement is not substantially higher than that of average

production. The new equipment acquired on a Project should be utilized at least to the extent of 75% of

its life.

Cycle Time:

Cycle time is the time taken by the machine to complete one full cycle operations. As mechanized

construction operations are production operations they comprise of a cycle which is repeated over and

over again. Sometimes many times in a working hour. The cycle time for a machine is composed of

two components: fixed time and variable time. The variable time is the time usually spent on traveling

and is a function of distance traveled and speed of the unit. The fixed time comprises of the time spent

in the performance of all operations other than traveling, such as loading, dumping, turning, gear

shifting, acceleration etc. Representatives values of fixed time are available in tables supplied by

manufacture of equipment or may be estimated though a time motion study of the operations. The

variable time can be computed from the distance and the probable speed of the machine.

A. JOB Factors

It can be understood that the physical features of a job will after the performance of equipment e.g. the

type of material would determine how much load can be carried in a scraper bowl. Similarly, the rolling

resistances of the haul road will possible ranges of variation, so that these can be used in estimating

the realistic production of equipment on any job:

1. Swell and shrinkage factor for materials. 2. Rolling resistance of haul roads, which may vary from 20-40 kg per tone.

3. Gradients, which can be favorable or unfavorable, for loading and for travel.

4. Tractive efficiency, which will determine how much traction, can be applied before slippage will

occur.

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5. Reduction of horse power of engine due to attitude. This will be at the rate of 3 percent loss in

horse power per 300 metres, above 1, 000 metres.

6. In case of power shovels or draglines, the angle of swing, and depth of cut.

7. Climate and terrain conditions.

8. Moisture content in earth and stone metal. Such factors can be assessed at each job, and the estimator can make an intelligent guess, as to how they affect the production of equipment

9. Other local factors.

B. Management Factors

These will be: 1. Operator‘s efficiency depending on the training and experience of the operator. 2. Capacity of machine, type of transmission, speed etc.

3. Proper matching of equipment, sizes and numbers, so that the most important production

equipment is not kept waiting or idle.

4. Time required for on-the –servicing and maintenance.

5. Unavoidable delays in combined operation of all equipment‘s. For this calculation of the production of earth – moving equipment.

6. Availability of well equipped workshops, maintenance facilities, spares parts stock, etc.

7. Anticipated job and efficiency factors.

8. Good management worker relationship.

9. The management factors may vary from 60 percent for an average job to 75-80 percent for a

well managed job.

10. If a manufacturer specifies production of his equipment as x cu. Meters per hour, under ideal conditions. The actual production on the job, whose combined, job factor being 80 percent and management factor 70 percent will come to

a. x (0.8) X (0.7) = 0.56x.

11. In case manufacturer‘s output tables are not available, it is possible to calculate the production of equipment by making a time study of the job, calculating the loading time, travel time, delay time etc.

12. In assessing annual production of equipment, it is necessary to estimate the number of days of

work that can be done at a site, or the total number of hours that can be achieved in a year.

As an average figure, 150-200 days per year or about 1,00 to 1,500 hours per year of production work per equipment may be assumed.

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PROCEDURE FOR WORKING OUT REQUIREMENT The following steps are involved in designing construction plant and equipment, in the order these are listed below: 1. Estimate the total quantity of work to be done (such as cft, cyd, cum of earth work or concrete

placement). For earthwork use bank volume. 2. From the construction schedule find probable working time available (such as working hours of

working days to complete the quantity found in step 1)

3. From steps 1 & 2 above, find average rate of production per unit of time (such as B cyd/hour)

required to complete the work by dividing quantity found in step 1 by time as estimated in step 2. 4. Select a suitable size, and find its cycle time and from this cycle time the number of cycle

performed/hour. Then ideal output of the machine/hour = machine capacity x no. of cycles per hour. Consult production tables of machine. If available.

5. Scale down the ideal production as calculated in step 4 to probable value which would be

actually realized by using suitable efficiency factors.

6. Find the average number of machines required to achieve the target production by dividing quantity found in step 3 by quantity found in step 5.

7. Add 10 % to 20% additional capacity for peaking requirement.

8. Add stand by capacity of 10 to 30 % to serve during breakdowns, contingencies etc.

FABRICATION Fabrication, when used as an industrial term, applies to the building of machines, structures, or

process equipment for any process, chemical, petrochemical, Mechanical , electronic, operation and

maintenance. Type of industry by cutting, shaping and assembling components made from raw

materials. Small businesses that specialize in metal are called fab shops.

Steel fabrication shops and machine shops have overlapping capabilities, but fabrication shops

generally concentrate on the metal preparation, welding and assembly aspect while the machine shop

is more concerned with the machining of parts.

Fabrication when used in Construction Industry is the process of joining metal sections in the form of a

structure or frame or a skid mounted machine assembly.

1) Preparation of Metal sections: setting up, fixing in of various parts in the correct position and

joining by various methods like soldering, Brazing, welding, bolting or riveting and

2) Finishing- Finishing may involve cladding or it may even mean heat treatment of joints

especially when two parts of heavy metal section greater than 18 mm thick steel parts are joined

by welding.

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Definition of Fabrication –as applicable to Industry and construction

1.0 DEFINITION

Fabrication is the process of joining metal sections in the form of a structure or frame or machine tool

assembly. In this process, the following are necessary:

1. Metal sections

2. Preparation of metal sections,

3. Setting up or fixing in, of various parts in the correct position and joining by various

methods like soldering, brazing, welding, bolting or riveting, and

4. Finishing, sometimes with heat treatment.

1.2 ELEMENTS OF COST OF FABRICATION

For the purpose of estimating the cost of fabrication of a work, the following costs pertaining to the

fabrication work should be determined:

1. The Cost of the material directly used in the fabrication.

2. The cost of preparation of the material. This includes cost of cutting also.( Ex: edge

preparation and set up cost)

3. The cost of joining the parts by welding or riveting etc. ( by use of filler material)

4. On-cost or overhead costs.

2.0 JOINING METHODS

Fabrication work consists of various joining methods such as (I) lap joint, (ii) butt joint,

(iii)tee joint, (IV)corner joint, and (V) edge joint.

Sometimes, edge preparations are also involved in fabrication.

Figure A shows the different kinds of joints. Figure B shows the various methods of edge preparation

for joint fabrication.

3.0 Types of Welding Process

For estimating the cost of various elements in the fabrication work, the types of welding processes in

use, in general, may be classified as (a) Fusion Welding, and (b) Pressure Welding.

3.1 FUSION WELDING

In this type of welding, the parts to be welded are raised to the fusion temperature and then allowed to

solidify without application of pressure.

Gas Welding, ARC welding, THERMIT welding are the important processes under the category of

fusion welding.

3.2 PRESSURE WELDING

Pressure welding is another process of joining parts, in which the parts to be joined are heated to a

plastic state and then forced together by external pressure. The important processes that come under

this category are

a) FORGE WEDLING

b) RESISTANCE (ELECTRICAL) WELDING c) PRESSURE GAS WELDING.

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Electric Arc welding for fabrication work is very commonly employed in industries and in construction

site as compared to other methods.

For estimating the cost of electric welding, the following costs are included

1. Material costs

2. Labour cost

3. Welding cost

4. Cost of power

5. Finishing cost (Post-welding treatment cost)

6. Overhead cost. ( Job overheads, administrative overheads, Profits)

Table:-1

ELECTRIC ARC WELDING DATA FOR WELDING ONE METRE LENGTH

_____________________________________________________________________

Plate Electrode Length of Welding Power consume-

No. Electrode in Time in kwh

Thickness cm min

In mm

3 ` 10 60-70 6-7 1.4

5 8 70-80 10-12 3.1

10 6 100-120 20.25 3.0

15 6 175-200 35-40 3.7

20 4 200-500 40-45 4.8

25 1/4 330-350 60-70 6.5

4.0 CLASSIFICATION OF VARIOUS COSTS OF FABRICATION

Material Cost

This includes the cost of the metal sections and also the cost of other materials that go into the

fabrication like fit up materials etc. .

Labour Cost

Labour cost includes the preparation and fit-up cost and other expenditure before welding.

Actual Welding Cost

This is the cost of materials like electrodes, filler rods, fluxes, consumables like gases used

Oxygen , acetylene. Inert gases like Nitrogen, Argon etc. and energy used, and cost for a

qualified or experienced welder performing the fabrication.

Finishing Cost

This is the expenditure involved for finishing the welding joints and cost of heat treatment, if any.

Overhead Cost

Overhead cost is the cost of depreciation on equipment and other facilities connected with

welding. (i.e. Job over heads, administrative overheads and Profits)

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The consumption of gas and cutting speeds may be obtained from the standard tables

supplied for the purpose of estimating the cost.

Example: Table-1

CLASS EXERCISE:

Estimate the time required for the fabrication of an open tank of size 40 X 40 X 40 cm by gas

welding done on inner sides only. Assume fatigue allowance to be 5%. It is fabricated from

sheets of size 40 X 40 X 0.3 cm.

(Data provided: Speed of gas welding on 0.3 cm sheet is 12 min/meter length)

Solution:

Material Cost – Not given

Cost of preparation, cutting

And fixing in position – Not given

Actual welding time alone is to be determined.

Total length of weld=8 X 40 = 3.2 m ( it is assumed the top cover is left open)

Rate of welding = 12 min/meter length

Time required to weld 3.2 m = 3.2 X 12 = 38.4 min

Giving 5% fatigue allowance,

Time required to weld = 38.4 X 1.05 = 40.3 min

Total time taken to weld a tank = 40.3 min

Example

A cylindrical boiler drum 2.5 m X 1 m dia is to be made from a 15 mm thick mild steel plate. The ends are closed by

welding circular plates to the drum (Fig-c) The cylindirical portion is welded along the longitudinal seam. Welding is

done on both inner and outer sides. Calculate the electric welding cost using the following data.

Rate of Welding = 2 Meter per hour length on inner side and 2.5 Meter per hour for outer site.

Cost of electrodes = Re. 0.60/meter

Length of electrodes required = 1.5 meter per meter length weld.

Power = 4 Kilo Watt Hour per meter length weld.

Power Charges = 15 paise/KW h

Labour Charges = 80 paise/ hour.

Other overhead costs = 200% over the prime cost

Discarded electrodes = 5 %

Fatigue and setting up time = 5 % of welding time

Solution:

Total length of weld on outer side is equal to length of the inner side which is the sum of the length for welding

circular plates and length for welding seam joint.

Total length = 2 ( pie X 1) + 2.5 = 8.78 m

Labour charges

Welding time for outer

Welding = 8.78 m = 3.51 h

2.5

Welding time for inner side 8.78 h = 4.39 h

2

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Total welding time = 3.51+4.39 = 7.90 hours

Fatigue and set up charges

@ 5% = 7.90 X 1.05 = . 8.295Hrs

Total labour charges = 8.295 X 0.8 = Rs. 6.63 say Rs 6.70………….(A)

Cost of electrodes

Length of electrodes required = 8.78 X 1.5 m = 26.34 m

Cost of electrodes considering 5% discard = 26.34 X 1.05 X 0.6 =

Rs. 16.60……………(B)

Cost of power

@ Rs. 4.00 KW h/m and @ 15 paise / KW h = 4.00 X ( 8.78 x2) X 0.15

= Rs. 10.536 or Rs. 10.54…( c)

(*There are two sides – inner side and outer side.)

Over heads

Prime cost = Direct labour cost + Direct material cost

=6.70 + 16.60 = Rs. 23. 30

Overhead cost = 200 % of prime cost

= 2 X 23 30 = 46.60

Total cost = prime cost + cost of power + overhead cost

= 23.30 + 10.54 + 46. 60 = Rs. 80.44

REPLACING EQUIPMENT An equipment once purchased need not be kept till it becomes unserviceable. In its useful life,

every equipment passes through a period of most economical operation and there is also a

period when it ceases to be economical. It is at this uneconomical point of time that an

equipment should be considered for replacement. The replacement cost is the cost incurred for

acquiring an equivalent new equipment after adjusting the price of disposing-off the old one.

The replacement time is difficult to determine as it depends upon many cost factors such as

depreciation cost, investment cost, operations cost, down-time cost, obsolescence cost,

inflation and the new equipment purchase cost. Some of these cost computations require in-

house records and equipment marketing experience. A replacement decision involves analysis

of mathematical models incorporating a large number of variables. This analysis aims at

determining the optimum time in equipment life at which the equipment should be replaced for

maximizing profits or minimizing operating costs. There are a number of methods of analysing

the economics of equipment replacement. A simple approach is to consider the resultant effect

of replacement costs during each year of operation and identify the time which corresponds to

the lowest cumulative cost per hour of operation.

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The typical replacement costs considered during the analysis are as follows:

(a) Depreciation cost

(b) Investment costs

(c) Down-time costs

(d) Obsolescence costs

(e) Replacement cost.

The table depicted below gives the methodology adopted for evaluating various hourly costs

affecting replacement decisions. The summarized effect of costs indicates an approach to

determine the most economical time when the equipment should be replaced.

Equipment Replacement Decision Data

Number of Years

Code Basic Data Unit 1 2 3 4 5

A Predicted sale-value

(end of year) $ 75000 60000 45000 30000 20000

B Assessed machine

utilisation hrs 2000 2000 2000 2000 2000

C Cum machine

utilisation hrs 2000 4000 6000 8000 10000

Depreciation Cost

D Yearly depreciation $ 25000 15000 15000 15000 10000

E Cum depreciation $ 25000 40000 55000 70000 80000

F Depreciation/hour

(E/C) $/hr 12.5 10.0 9.17 8.75 8.00

Investment Cost

G Investment

(beginning of year) $ 100,000 75,000 60,000 45,000 30,000

H Deduct depreciation $ 25000 15000 15000 15000 10000

I Investment (G – H) $ 75000 60000 45000 30000 20000

J Average investment

(G + I)/2 (during year) $ 87500 67500 52500 37500 25000

K Investment cost (15%

per year) 13125 10125 7875 5625 3750

L Cum investment cost $ 13125 23250 31125 36750 40500

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M Cum investment

cost/Hr (L/C) $/hr 6.56 5.81 5.19 4.59 4.05

Down-time Costs

N Assessed availability % 97.5 95 92.5 90 87.5

O Machinery not

available % 2.5 5 7.5 10 12.5

P Machinery non-

utilisation hrs 50 100 150 200 250

Q Predicted hiring

charges per hour $/hr 30 32.5 35 37.5 40

R Down-time cost $ 1500 3250 5250 7500 10000

S Cum-down-time cost $ 1500 4750 10000 17500 27500

T Down-time cost/hour

(S/C) $/hr 0.75 1.19 1.67 2.19 2.75

Cost of Obsolescence on Performance

U —Assessed

obsolescence (I) — 5 10 15 20

V

—Shortfalls with

respect to new model

(T × B)

hr — 100 200 300 400

W —Hiring charges per

hour $ — 32.5 35 37.5 40

X —Obsolescence

costs $ — 3250 7000 11250 16000

Y —Cum obsolesence

costs $ — 3250 10250 21500 37500

Z —Obsolescence cost

per hour (Y/C) $/hr — 0.81 1.71 2.69 3.75

Total replacement

costs/hr (F + M + T +

Z)

$/hr 19.81 17.81 17.74 18.22 18.55

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Machines/machine elements/mechanisms.

CONSTRUCTION EQUIPMENT IS DEFINED AS

“ machine to give desired / designed out put with available input, using mechanisms and machine

elements using mechanisms like quick return mechanisms, crank shaft, crank mechanisms, coupling

mechansims and machine elementslike pulleys, belts, ropes chains, levers, wheel and axles, gears,

cluthes, brakes etc. in one way or the other. ‖

Introduction to Machine and Mechanisms

Machine: Machine is a contriviance to convert energy in an available form to do useful work.

A machine will be found to consist of an assembly of links or pieces.

Example: a petrol engine converts the heat of combustion of the fuel petrol or diesel into

mechanical work obtained at the crank staft. This mechanical work can in turn be used to run a

water pump or a machine tool in a work shop or a construction equipment at a construction site.

.

Mechanisms:

This has two aspects:

a) Kinematics of Machine: it deals with the relative motion between the parts, neglecting the

consideration of the forces.

b) Dynamics of Machine: it deals with the forces acting on the parts of the machine.

Dynamics may further be divided into

Statics which deals with the forces, ignoring the mass of parts

Kinetics which deals with inertia of forces due to mass and motion considerations.

Difference between machine and structure.

Machines serves to modify and transmit energy or force or motion. Relative motion exists

between members. Eg,. Diesel engine- crank mechanism- crank and crank shaft.

Structure serves to modify and transmit forces only. No relative motion exists between

members. Eg. Roof truss.

INPUTS TO MACHINES

The inputs into machines are the motive source of power:

Fuel: Oil, Gas – furnace oil, petrol , diesel, cng or LPG gases

Suspended or saturated or superheated water: steam or super heated steam

Hydraulics or pneumatics: water, compressed air

Electricity.

PRIME MOVER: Prime mover is the source machine to derive the output. Prime movers are

Driving

Machine which could be a driving machine. They can be an ELECTRTIC MOTOR, ENGINE,

TURBINE etc.

ENGINES are driven by burning oil and gas inside a enclosed place. The heat contained the burning

fuel oil or gas gives energy . The energy developed in the form of pressure wave within an enclosed

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space ( cylinder of the engine) expands to push a machine element ( PISTON) . Through a suitable

designed mechanism/s ( crank shaft and cranking mechanism converts the reciprocating motion of one

element into rotatingmotion of another element constituting a flow work from the output shaft of the

engine. This available flow work is converted into the desired work or desired task further by suitable

mechanisms and machine elements.

CLASSIFICATION OF ENGINES

By and large the motive power used in the running or operation of construction Machinery is either

Petrol engine, diesel engine or dual fuel engines (oil and gas) or electric drives using Electric motors.

Since electricity will not be available at all const. sites the electricity power is generated by utilities like

Generator or compressors and the source fed to machines to run the machine.

Machines are run with petrol, diesel , steam, water (water turbines.)

Petrol engines follow a Thermodynamic cycle and it is called as OTTO CYCLE

Diesel engines follow a Thermodynamic cycle and it is called as DIESEL CYCLE

Steam engines follow a thermodynamic cycle called Joules cycle.

What is thermodynamics? Thermodynamics is the study of conversion of heat contained in

thermodynamic fluids into work and its various cycles.

Thermodynamics cycles.

OTTOCYCLE:comprises of 4 processes to complete the cycle

a) Adiabatic compression of the mixture of air fuel

b) Combustion of mixture at constant volume.

c) Adiabatic expansion of combusion products with output of work.

d) Discharge of exhaust gases at constant volume to the atmosphere.

Efficiency of the engine = 1 - 1 / r ** (k-1) where r= compression ratio

K = specific heat ratio = cp/cv

DIESEL CYCLE: Comprises of the following 4 processes to complete the cycle.

a) Adiabatic compression of fuel air

b) Liquid fuel injection at constant pressure maintained by vapourising during expansion ve.

c) Adiabatic combustion of the fuel and producing a pressure wave resulting in expansion

d) Discharging products of combustion at constant volume.

Efficiency of the engine = 1 - (rc)** (1-k) / k x ( rc**k - 1 / rc -1 )

rc = compression ration = V1/V2 re = expansion ratio = V2/V1.

Power developed by engines.

Joules cycle : which is a thermodynamic cycle used in all Heat engines has the following process.

A) Generating high motive fluid by adding heat at constant pressure.

B) expansion of steam to do work.

C) condensation of the fluid. ( two phase flowing fluid ) steam

D) adiabatic compression of the condensed fluid .

This is popularly used in all steam engines and steam generating plants.

POWER DEVELOPED:

The power developed in an engine is called the Theoretical or ideal power and it is given by the

notation Indicated Horse power.

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The power available at the end or shaft of the machine which is the useful power is called the BRAKE

HORSE POWER (BHP) OR shaft horse power or it is termed in construction industry as frictional horse

power (FHP). The efficiency of the conversion from IHP TO BHP is 85 to 90 percent. The overall

efficiency of conversion form IHP to useful work output varies widely from 20% to 80 % based on the

overall system design and the efficiency of each subsystem in the engine train.

Expression of Brake Horse Power:

BHP = 2 X TT x N X T / 4500

N= is the speed of the engine ( in revolutions per minute)

T= torque developed by the engine.( Kg-cm)

ENERGY, WORK AND POWER

Energy is the capacity to do work

Work – shaft or flow work ( rotational, fluid flow like in hyd.turbines)=force times the distance.

Power is the rate of doing work = WORK/ TIME = FORCE X DISTANCE BY TIME

DISTANCE / TIME Constitutes velocity

Hence power = Force x velocity. In all equipment Basics we measure the force required to haul the

engine which constitutes the FORCE. And velocity is measured by distance and time and the power of

the machine is computed. (The important parameters concerned with construction equipment are

covered in the equipment basics. )

MECHANISMS

The transfer of power to useful work is carried out by Machine elements through suitable Mechanisms (

Mecanics or theory of Machines)

Popular mechanisms used are:

a) Crank and Piston = converts reciprocating to rotating or rotary motion

b) Lever and fulcrum mechanism= simple machine applies efforts to life load by using lever with a

fulcrum point.

c) Belting : to transmit power from driver to driven.

d) Pulley drives: to change speed or to change direction of rotation.

e) Geared Mechanism : to change speed and torque.

f) Clutch : to engage and disengage transmissions.

g) Braking Mechanism: to bring to halt or stopping of a drive train or coasting down the speed.

h) Coupling : to link driver to driven and allowing for flexibility between the driver and driven train.

Eg. OLDHAMS COUPLING MECHANISM : applied to transmit power between driver

and driven which are mis aligned axially .

a) Hydraulics: used as element for transmit power and torque.

ELECTRICAL DRIVES

What is an electric motor?

A machine to convert electrical energy to Mechanical energy ( rotational output)

Name plate details. Power in kw, speed, phase, cycles, efficiency, motor rating: intermittent or

continuous, moment of inertia, class of insulation, area of operation: dust or dust free. Type of

loading: regular or cyclical.

DC Motors, AC Motors, induction motor, synchronous motors.

How do you select a motor for a given application: study the power , speed , torque characteristics,

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power vs. speed characteristics and match the MI of the driver to driven masses.

PULLEY SET S

Pulley and axle= These are very common machine elements used from time immemorial for lifting

loads. A good example of the pulley and axle is that of the one used by people to lift water from well. A

simple system is given below

EFFORT

In the above E = L , MA =1

When you arrange pulleys in groups, MA greater than 1 can be derived by suitable arrangements.

EFFORT= Load / no of pulley at the fixed end

if load = 100 kg EFFORT = 100/2 =50 KG , MA 100/50 = 2

Tyres

The two popular types of Machine elements sued in the ground drives are :

Track Mounted

Tyre mounted

Tyre is the element that grounds construction machinery.

The Characteristics that are to be considered are:

a. To roll the machinery on the surface of the terrain or a paved or made up path

b. Must absorb a part of the shocks and transmit them to the shock absorbers

c. Acts as cushioning to reduce vibration on the machine

d. Must reduce the friction

e. Reduce the attractive effort

Tyre must take the bearing load, must be durable, should provide smooth ride and suitable designed to

roll over in rough terrain, must have a firm grip to the ground.

Classification: high air pressure, low air pressure tires.

Pneumatic and solid tires.

Normal and radial tires

Importance of Tyres for construction equipment:

Cost of tyres is considerable hence has impact on the operating cost of equipment.

Can be a dictating factor for project operating cost in mechanized construction projects like highway

road making projects.

The life of tires depends upon its construction and use

One of the factors considered besides construction is the subject of alignment of the wheel . The tires

which are properly aligned and balanced and operated at the correct recommended air pressure will

have a better life than those without balancing, aligning and operated under a deflated pressure.

Types of Tyres Used

a. Pneumatic tire. Pneumatic tires are designed to cushion the vehicle and its load from the

shocks and vibration resulting from road inequalities. The springs and shock absorbers protect

primarily those assemblies which are mounted above the axles. Unsparing parts such as

wheels, axle‘s assemblies and brake mechanism at the wheels, depend entirely upon the

resiliency of the tires for protection from the road shocks.

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Pneumatic tire can be : a)Tube tire

b) Tubeless tire

Gears & Drives.

Gears are machine elements to transmit motion from one shaft to the other especially when they

are in close proximity and in contact with each other. Gear wheels employed to transmit motion

from one shaft to the other is called a gear train. The gear trains may be classified broadly into

the following categories.

Simple train of gears

Compound trains of gears

Reverted trains of gears

Epicyclical trains of gears

The classification of gears are also dependent on the type in which the teeth of the gears is formed like

for example

a. Helical form of gear teeth

b. Herringbone gears

When the driving and driven gear shaft is parallel they are named as spur gear drive, when the

driving and driven shafts are at 900 . They are called as bevel gear drive.

Two circle representing two gear wheels constitute a simple train of wheels with teeth meshing to

provide a positive drive. Let ―1‖ represent the driver (prime mover end) and ―2‖ represent the driven or

follower. We have the following relation.

w2/w1 = T1/T2=N2/N1=PCD ―D1‖/ PCD ―D2‖

w = angular velocity , T = Number of gear teeth

N = Speed of rotation in revolution per minute and D stands for pitch circle diameter (diameter of

contract points of the gear teeth)

Compute the number of teeth in the follower gear given the speed ratio (driven to follower) is 3 and the

number of teeth in the driver is 60.

Given N2/N1 = 3 and 60/T2 = 3 and T2 = 60/3 = 20

Problem

Compute the BHP required at the Diesel engine shaft to drive the shaft of an aggregate crusher in

the following arrangement. Assume there is no slip between the gear teeth of the driver and driven

gear. The speed of the Diesel engine is 1500 rpm. The pitch radius of the spur gear mounted on the

diesel shaft is 10 cm and the tangential force coming at the gear teeth is 50 kg (f).

1 HP = 75 kg – Meter/sec or 4500 kg -cm /minute.

Torque on diesel engine shaft is 50 x 10= 500 kg cm

Power = 2 x x N x T/ 4500 = 2x3.14 x 1500 x 500 / 4500

= 1046.6 or say 1050 HP

In terms of electrical units it will be

=1050 x .746 KW = 783 KILO WATT.

Assuming an efficiency of 85% the input power required is

input power = 783 / 0.85 = 921 KW.

DIESEL ENGINE CAPACITY WILL BE 1000 KVA

Wire ropes

Wire ropes are machine elements to be used as

Lifting tackles, towing elements, and for fastening purpose.

The formation and rating of these elements needs to be understood for application in construction

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equipment.

When procuring and using them the correction specification needs to be made and it needs to be

subject to inspection and test as per statutory tests.

The specification for a typical wire rope is as follows:

Metal wire rope ND 12 mm 12/10 with metal core or non metal core, for lifting purposes to be used in

cranes. ( BIS spec nos to be referred.)

The rating is mentioned as SWL AND BREAKING FORCE (KN)

SWL= SAFE WORKING LOAD. ULTIMATE LOAD/FOS.

ND= nominal diameter, 12 strands, 10 wire in each strand with core metal.

Brakes

Brakes is a machine element and its principal object is to absorb energy, Commonly the brakes are

used to absorb kinetic energy of the moving parts to stop them or to slow them down, but other uses of

brakes for absorbing potential energy as in the case of hoists or elevators are common.

A simple braking mechanism with hand lever is explained below with principles of working.

Tb = Brake torque,

u = coeff of friction

W = radial operating force

P = Normal reaction in radial direction

F = force applied at lever

r = radius of drum

For the lever to be in equilibrium sum of M = 0

Sum of Fx = 0 sum of Fy = 0

Taking moments about pivot ( o )

Therefore we have P x b – F x a1 = 0, F = P x b/a1

Take moment about (o2)

P x b – uPxd – F x a= 0, F = P x b-uP x d/a

Taking moment about (o1)

P x b – uPxd – F x a= 0, F = ( P x b + uP x c) /a

Braking in machine can be mechanical powered or hydraulic powered or air powered (pneumatic

brakes). The brake liners must be kept in good condition for brake engagement as the soundness of

the material is a dictating factor in good functioning of brake.

Couplings: These are elements joining the driving and driven shafts of machines. There are a number

of types

a. Rigid coupling

b. Flexible coupling

c. Hydraulic coupling

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Bearings

Bearings are machine elements to carry the load the reduce the friction between moving and static

part/ component. There are two types of bearings.

Friction bearing – Journal bearing, thrust bearing (surface contact)

Anti friction bearing – Ball bearing, needle bearing, roller bearing, conical roller bearing (point or line

contract). Bearing are stipulated by the duty and accepted life in hours. Duty is based on duty cycles

as intermittent and continuous and by both static and dynamic load bearing capacity.

Certain bearing carry axial loads, certain carry thrust loads and there are certain bearing carrying both

axial and thrust loads.

Hydraulic

One of the power sources in construction Machinery is hydraulic power.

A hydraulic system has essentially the following components:

A hydraulic reservoir

Hydraulic piping system (comprising of pipes, hoses, flexible elements, couplings, valves,

solenoid values, pressure reliving devices)

Properties of a hydraulic fluid:

Must withstand pressures and temperatures

Low viscosity

Is preferably a mineral oil derivate

Torque Convertor/hydraulic Clutch Gear Box - Schematic

Preparatory questions

1) Define construction equipment

2) Differentiate between Machine elements and Mechanisms

3) Give examples of few Mechanisms and where they are employed.

4) what are the various Thermodynamic cycles applied in power engines.

5) what are the processes in a DIESEL CYCLE.

6) Draw a neat sketch showing the power derived from a prime mover of construction equipment with

its machine elements and mechanisms to carry out a useful work output.

7) What are the theoretical limitations for obtaining 100 % efficiency output in a construction

equipment.

Write short notes on: Brakes, MA of a pulley block, MA of a lever mechanism, Tyres, Wire ropes.

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Non-destructive Testing and Diagnostic Instruments

Non-destructive testing methodologies have been designed for the accurate measurement of

characteristics of parts of a machine, without in my way affecting that part physically or functionally.

These testing facilities are developing very rapidly all over the world, and are progressively being made

available indigenously as well. They are frequently being used and relied upon, for application and use

in predictive maintenance practices and systems. The operating parameters which can define the

health or condition of an operating machinery need to be monitored thoroughly.

In order to monitor the health of a machine, there are several parameters; these parameters are now

discussed.

(i) Process variables. These include pressure, temperature, flow of process

fluids, lubricating oil, seal oil, and cooling water circulation.

(ii) Mechanical running condition variables. These variables are:

a) Temperature of vulnerable machine components

b) Mechanical vibrations

c) Machine RPM

d) The relative motion of moving elements with respect to stationary elements of a machine

e) Crack detection.

(iii) Rotating machinery malfunctions. These include imbalance, misalignments, foundation

problems, fracture and warpage of casing due to a variety of loads such as thermal loads, and bearing

failures.

NON-DESTRUCTIVE TESTING METHODOLOGIES

In order to monitor the above parameters, a variety of non-destructive testing (NDT) methodologies

have been developed; some of these are now described in brief.

Boroscope

This is a tool that can be inserted into inaccessible places through small openings, and with its aid one

can see a highly magnified image of the part under examination, through an eyepiece, a prism, or a

reflector which has lighting arrangements.

Flexlscope

This is an instrument that is used to see contoured surfaces and U-bends, which are otherwise not

within easy reach or view.

Liquid Dye Penetrant

This dye can seep into minute surface openings by capillary action to detect surface cracks, porosity

and lamination.

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Magnetic Particle Detection

This technique is used for locating surface and sub-surface discontinuities in ferromagnetic materials.

When a test piece is magnetised and finely divided, the ferromagnetic particles sprinkled over the

surface forms an outline of the discontinuity formed by the magnetically held collection of particles,

indicating the size, location, shape and extent of the problem of discontinuity.

Eddy Current Testing

This method is employed to measure electrical conductivity, magnetic permeability, grain size, heat

treatment condition and hardness. The eddy current detects seams, laps, cracks, void and inclusions

and sorts out dissimilar metal compositions.

Ultrasonic Devices

These devices use beams of high frequency waves to detect surface/sub-surface flaws. The waves

travel through the material with attendant loss of energy and are reflected at the inner faces. The

reflected beam is analysed to define the presence/location of flaws, cracks, laminations, shrinkage,

cavities, pores, inclusions, etc.

Radiography

Because of the variation in the density and thickness of the radiographed item, it absorbs different

amounts of radiation energy, with the unabsorbed radiation passing through the part The radiation can

be recorded on film, or on to photo sensitive paper and viewed through a radiographic viewer to locate

defects.

Hardness Testers

A variety of hardness testers, such as the Rockwell hardness tester, the rebound hardness tester and

other allied tools, are available today. They are all portable and can indicate resistance to penetration

and wear.

Creep Tester

Creep is a phenomenon that results in permanent deformation and damage when an item has been

operating at high temperatures and stresses. The creep tester measures the changes that have come

about in the dimensions. This has to be done at periodic intervals.

Spark Testing

In this test, a visual examination of the spark pattern that emerges when an alloy is held against a

grinding wheel is used as an indicator for classification of ferrous alloys according to their chemical

composition.

Leak Testing

Here, the assembly is filled up with air up to a specific pressure, and then a testing is done with a soap

solution, halogen, helium or freon, to locate the leak.

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Time ----------------

Fig. 7,1 Vibralion

analysis.

Thermal Testing

The measurement of temperature can indicate abnormal or overhot conditions. The measurements can

be done by making use of contact thermometers, heat sensitive paint, heat sensitive stickers, infra-red

thermometers or optical pyrometers.

Acoustic Emission Testing

Acoustic emission is defined as a high frequency stress wave generated by the rapid release of strain

energy that occurs within a material during crack development or plastic deformation. This method is

capable of detecting the minutest of increasing flaws. There is no other NDT method which can match

its capability.

Holography

Holography is a three-dimensional image of a diffusely reflecting object having an arbitrary shape. Both

the amplitude and the phase of any type of wave motion emanating from the object are recorded by

encoding this information in a suitable medium. This reading is a holograph. It can be obtained by

using visible light waves and is known as optical holography or ultrasonic waves, called acoustical

holography. It is used for detecting/locating debonds within honeycomb core sandwich structures,

unbonded regions within pneumatic tyres, cracks in hydraulic fittings, stress of all kinds, corrosion,

cracking in metals, fatigue in turbine blades, etc. Acoustic holography has been used commercially for

inspecting various types and sizes of welds.

In Situ Metallography

The particular part to be examined is polished and etched in its location and the surface structure is

transferred to a thin film using suitable chemicals. Then it is examined under a microscope to review

the metallurgical changes that have taken place such as graphitisation, carburisation, intergranular

cracking, and grain-growth.

Strain Monitoring

Strain gauges arc used to monitor the condition of parts subject to strains due to variations in their

operating conditions. This is used extensively in aircraft testing during design stages and after

overhauls during test flights.

Vibration Monitoring

Vibralion in rotating machines is caused due to factors such as

imbalance, misalignment, looseness, cavitation, turbulence,

wear, bearing damage, coupling damage, and rubbing. As the

defects grow in magnitude, the vibration levels increase. By trend

monitoring, the faults can be identified.In vibration monitoring,

portable vibration analysers, digital vector filters, spectrum

analysers and oscilloscopes, and the data generated can pin-

point the cause of vibration (see Fig. 7.1).

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THE a-z OF DIAGNOSTIC INSTRUMENTS

More and more advanced portable diagnostic instruments are being developed each day. There are a

host of them; some of these are now described, giving their particular functional details.

Diagnostic Instruments

1. Pocket-sized thermistor thermometer. This is shaped like a pocket watch with battery and

probes, and gives a temperature reading within a few minutes.

2. Ultrasonic hardness tester. This instrument is used to read surface hardness in Rockwell C, of

bearing, races, shafts, etc. A light weight probe, which is held against the surface, makes a

reading. The answer is delivered in 2-3 seconds.

3. Ultrasonic corona detector. This device is employed to hear the 'carona* in the voids in cables

or in the splice insulation slung across insulators before the carona can damage the insulation.

4. Laser beam source and detector readout. This permits the alignment of shafts, fixtures, or

structures to be made even when the items to be aligned are hundreds of feet apart This is done

to a precision of 0.001 inch.

5. Pistol-grip static meter. This instrument measures the electrostatic charge on any surface at

which it is aimed from a foot away.

6. Portable sonic resonance tester. It measures the thickness and soundness

of concrete or wood, and can check the uniformity of fire bricks or metal.

7. Eddy current tester. This has a pointed probe which spots tiny

discontinuities on or below the metal surface without touching the object being

scanned.

8. Pencil-probe leak detector. A neon light within the transparent probe

Hashes whenever the point of the probe gets near a freon leak.

9. Tension checker (pencil sized) for V-belts.

Thermopile heat flow sensor. This gadget can be connected to any vacuum-tube voltmeter, and

then it can be calibrated to read the extent of heat loss due to insulation (B.T.U. per square ft per

hour) or to check the efficiency of the different areas on a heat transfer surface.

10. Stethoscopes. Overcoming external noise and disturbances, these can pick up mechanical

problems like bearing problems which develop within. There are electronic stethoscopes as well

as those commonly used by doctors everywhere.

11. Smoke bombs. These are used to ascertain the wind direction.

12. Thermistor thermometer. Unlike the pocket version, this is a probe attached to a flexible lead

on portable instruments. It reads the temperature directly and accurately.

13. Vacuum-tube voltmeter. This is characterised by its ability to read voltage across points in an

electronic system without drawing current from the circuit.

14. Fibre optic inspection probe. This enables one to make an examination of the internal

mechanism of a closed or inaccessible gear case or housing. Being avery small probe, it is a very

useful tool for the inspection of gear teeth, or for locating broken/lost parts within a rotating

machine.