Cons Eqt Handout 2

8/22/2019 Cons Eqt Handout 2

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1 ConstructionEquipment(UE502)

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Chapter1 IntroductiontoConstructionEquipment

Construction is vital for national development. It may be defined as the creation,renovation, repair and demolition of immobile structures and the alteration of natural

topography of the ground. Construction both the activity and the resulting product

are notably visible and tangible.

Construction reflects the economic, social and cultural activities and value of society.

The building and engineering projects with which people come in daily contact affect,

in some complex way, their moods and attitudes, their effectiveness and the quality of

their lives. Conversely, the traditions, aspirations and vitality of people are reflected in

their settlements and their constructed environments.Most construction projects are big and complex, both technically and commercially.

There is considerable specialization, both among types of construction and among the

site operations of a particular project. With the increasing, understanding of materials,

improved designs, improved construction and management techniques and

introduction of computers, modern construction is a multi-disciplinary activity.

Construction process in character of performance may be mechanized or non-

mechanized and in degree of complexity simple and complicated. For example use of

Bull Dozer is a simple mechanized work whiles excavation by power shovel ismechanized complex work.

Modern construction is becoming complex from time to time. Projects are quite big and

complicated. They require a long duration and huge fund. It becomes essential now to

use construction equipment to economies the cost of construction. It is not necessary to

use construction equipment for small jobs. In most cases the combination of manual

labor and machinery appears most justified.

Advantages of use of Equipment

Tough work (beyond the scope of manual), Where human labor is uncertain, The equipment are not affected by social and economic condition of the region, Due to use of machine proper planning of work can be made, which

consequently reduce the overall cost of project,

For huge work,


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For large quantities to be transported, Equipment help in rapid urbanization of country,

The Drawbacks of Using Machines are

Creates unemployment problem, Need maintained properly, High early investment, Needs foreign exchange,

Hence always a comparison is essential between use of machine and labor.

Factors to decide for use of equipment or labor:

Nature and magnitude of works, Is it essential to use machine? Arrangement of necessary technical support

1.1 Types and Classification of Construction Equipment

Machines and Mechanisms used in construction can be classed in respect to the kind of

job, nature of working process, the operation conditions, the type of drive, the capacity(output), the type of running gear, universality and the kind of control.

Equipments are used on almost all the project in one form or the other. Equipments are

classified as shown below:-

Earthmoving Equipment Excavating and Lifting Equipment Hauling and Placing Equipment Grading and Finishing Equipment Compaction Equipment Asphalt Mixing Plant and Asphalt Laying Equipment Pumping and dewatering Equipment Pile Driving Equipment Concreting Equipment Conveying Equipment


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Bridge Construction Equipment Foundation Equipment Pneumatic Equipment

Drilling and Blasting Equipment Shovel and Cranes Trenching Dredging and Tunneling Equipment Aggregate Production Equipmenti) Earthmoving Equipment

Earthmoving is a process of cutting and moving soil, rocks or trees from one location to

another and processing it so that it meets construction requirements of location,

elevation, density, and moisture content and so on.

The equipments like Bulldozers are very common of the entire earthmoving machine.

Bulldozer is most useful and most project sites require its use in one form or the other.

As earthmoving work comprises of Excavating and Lifting, Hauling and Placing, and

Compacting; the earthmoving equipment are those required to undertake these tasks.

Accordingly, equipments used are; for Excavation and Loading Backhoe, Face shovel,

Dragline, Clam shell, and Loaders; for Hauling and Placing Dumpers, Dump trucks,

Lorries and Conveyors; for Excavate load haul and place, Dozers, Scrapers and

Graders and for Compaction Rollers, Vibrators and Rammers.

Besides, earthmoving equipment can be categorized into fixed and mobile. Excavator is

under category of fixed while material carrying and pushing equipment are falling

under mobile.

ii) Excavating and Lifting/Hauling EquipmentThese are construction equipments used to excavate and load earth material for various

purposes. These equipments fall under i) Crane shovel family comprising of

Backhoes, Face shovels, Draglines and Clamshells; ii) others comprising of Loaders and

Bucket wheel excavators.

The shovel family construction equipment comprises of three major assemblies; these

are:-

A carrier or mounting, A revolving superstructure containing the power and control unit and


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A front end attachment.The carrier or mounting can be crawler, truck or wheel mounted type, depending on

the mobility required of the equipment. If the job is scattered and requires higher

mobility then the wheel mounted is chosen and in case of concentrated work and softgrounds crawler mounted is preferred.

The power required depends on the type of material to be excavated, the accuracy of

excavation and dumping.

The front end attachment is selected depending on the distance from the digging point

to the material dumping point, which must be moved by the machine. They could be

hydraulic or cable operated.

Hydraulic Excavators (Backhoe & Shovel)

These two excavators have hydraulic operated front end attachment and are hydraulic

excavators except for previous times and in a very few instances at present.

The technical characteristics or measure of the hydraulic excavators are its weight and

motor output. Based on these two parameters they are divided into three groups:-

Group-I: with weight of 10, 15, 20 and 25 tons. Their output is less than 150 KW. They

are either crawler or wheel mounted. They are transported by low bed trucks or are self

driven, if mounted on wheels.

Group-II: with weight of 30, 45, and 55 to 60 tons. Their output is 125 to 300 KW. They

are manufactured only with crawler mounted and are transported using low bed

trucks. They are usually manufactured as backhoes.

Group-III: In this group one finds excavators with weight of 70, 135, 200 and 225 tons.

Single piece with weight of 350, 500 and 630 tons or higher are sometimes

manufactured for rocky excavations open pit mining and cement mining. They are

mostly transported dismantled and are assembled on the site. The power ranges above

300 KW.

Hydraulic System and Control

The equipment has programmable electronic control system, which enable higher

output and economical operation. They have built-in load sensors which control or

regulate the energy used with the respective demand. Overloading of each driving

motor is blocked


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Front End Attachment

Hydraulic excavators of group-I are usually equipped with adjustable booms. This

arrangement increases the flexibility and mobility of the front end attachment and also

increase the effective radius and height.

The mobility and flexibility is of an advantage in particular for trench excavations.

Hydraulic excavators of group-II are usually equipped with mono block boom and

backhoe system. The mono block type is more stable than the adjustable type and also

cheaper in fabrication.

The third group is meant for rocky excavation in quarry sites, against vertical faces. As

a result they are mostly shovels.

The excavators can be categorized as Shovel and Back hoes. The shovel is equipmentused mainly in quarries, pits and on construction sites and used in excavating/loading

blasted rock. They are usually deployed for digging above the machine base line, and

they have faster and more accurate digging and dumping cycle. The shovel can be cable

operated or hydraulic operated machine. Back hoes are excavators designed primarily

for excavation below grade. Thus in a backhoe operation, it is always advantageous to

position the hauler at a lower level with respect to the excavator.

The only difference between the shovel type excavator and the backhoe type is the

direction of the bucket. The backhoe as its name implies is excavating towards itself andthe shovel away from itself.

There are also the so called telescoping excavator and walking excavators. The

telescoping excavator is a hydraulic excavator with same type of mounting and

revolving superstructure but with different front end attachment. The front end

attachment is a telescoping boom, which can rotate 360o and can be lifted up to 35o up

and 85o down with respect to the horizontal. It can be extended up to 12 meters, with

each telescoping unit measuring 4 meters. The walking excavator is similar to the other

excavators except that its mounting consists of two legs on wheels and two legs on

telescoping pedestals, which are used to step forward and backward under difficult

situations.

iii)Hauling and Placing EquipmentHauling units transport materials from one place to the other. Hauling units are mainly

trailers pulled by tractors, trains or trucks.


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The choice of one particular hauling unit is dependent on the working conditions and

distance to be transported. Trucks are the most used transport/hauling equipment and

they are commonly called dump trucks. They can be front dumper, side dumper, rear

dumper or bottom dumper trucks.

The selection of dump trucks is based on nature of work, nature of route, matching

capacity and whether it on highway or off-highway.

iv)Grading and Finishing EquipmentGrading is the process of bringing earth work to the desired shape and elevation. Finish

grading involves smoothing slopes, shaping ditches and bringing the earthwork to the

elevation required by the plans and specifications.

The equipment mainly used for these operations is the motor grader. Motor Grader isequipment used for grading, finishing, trimming, bank sloping ditching, backfilling and

scarifying. Grader is operating using a blade mounted under its body.

v) Compaction EquipmentCompaction is the process of increasing the density of a soil by mechanically forcing the

soil particles together, thereby expelling air from the void spaces in the soil.

Compaction is used to:

Increase bearing strength, Reduce compressibility, Improve volume change characteristics, Reduce permeability

Degree of compaction depends on; Soil property, moisture content, compaction method,

amount of compaction effort, thickness of soil layer and material gradation.

The three basic compaction forces are; static compaction/weight,

manipulation/kneading and dynamic compaction.

Static Compaction: Compaction is achieved by pressing. To achieve good compaction

bigger weight is required. Nowadays static compaction alone is not used.

Manipulation: This is a process of expelling air from the void space by continuously

bringing the material to be compacted up and down.


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Dynamic compaction: this involves impact and vibration. Impact and vibration have the

same method, but the difference is in their frequency only. Compaction above 50 Hz is

vibration and anything below that is impact.

Plain steel rollers, Vibrating rollers, Temping rollers, Pneumatic tired rollers are some of

the most common compaction equipments.

Plain steel rollers or smooth drum roller weighing from 5 to 15 tones are used for

ordinary rolling works where deep compaction is not required. Rollers can be a two

wheel or three wheel tandem rollers. The rollers are designated in terms of weight

which is stated in tones. A 8/10 tones indicates that minimum weight of machine is 8

tones and can be ballasted to give a maximum weight of 10 tones. For compacting

earthwork in embankment or canals where compaction is required to be done to a great

depth, sheep foot temping roller is used. Pneumatic tired rollers compact the soilthrough static weight kneading and vibrating. It consists of ballast box mounted

between two axles.

Manually propelled self-propelled vibro plates are used for consolidation and

compaction of soils where large units are not practical.

vi)Asphalt Mixing Plant and Asphalt Laying EquipmentTar and bitumen heaters are used to heat tar and bitumen for road construction and

maintenance works. Nominal capacity of tar and bitumen heaters are 100, 300, 500,1000, 1500, 2000, 3000, 5000, 7500 and 10,000 liters.

Tar and bitumen sprayer is a bitumen boiler fitted with a pumping and spraying

equipment. Nominal capacity of tar and bitumen sprayers is 1000, 1500, 2000, 3000,

5000, 7600 and 10,000 liters.

vii)Pumping and dewatering EquipmentMany times water creates problem at construction sites. Under such circumstances we

need the area to be dewatered to ease the construction. To dewater the area Pumps are

required. A pump is a device which transfers the mechanical energy supplied from an

external source to the liquid blowing through the machine.

Pumps can be submergible or external types as the case may be. Pumps are usually

classified into two:


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a) Positive displacement pumps; the operating force is applied directly to the liquidthereby increasing the energy of the liquid. Rotary pumps or reciprocating

pumps are the examples of this type.

b) Rotodynamic (centrifugal) pumps; employ a rotor moving in a liquid in thecasing. The movement of a rotor imports high velocity to the liquid which is then

discharged due to the centrifugal force.

viii) Pile Driving EquipmentPiles may be driven into the ground by using pile driver. A pile driver consists of a

device to hold a length of pile in place, a hoist to lift it into the vertical or inclined

position and hammer device to provide impact energy required to derive a pile.

ix)Concreting EquipmentConcrete referred to as plain concrete is a material obtained by cementing together with

inert material such as sand, gravel or some other suitable material which is hard and

durable. It is very strong in compression.

In general the following operations are involved for production of concrete:-

a) Batching the materialb) Mixingc) Handling and transportingd) Placing finishing and curing

Different operations involve different equipments.

Batchers: Batchers are used for proportioning the ingredients of concrete. Materials are

batched volumetrically or weight batching may be done. For large and important jobs

weight batching is more or less essential. If a project is large enough to justify the

additional investment in equipment for handling and batching aggregate, an elevatedstorage bin equipped with a weighing batcher should be used. It will make necessary to

provide a clamshell or other suitable equipment to handle and transport aggregate from

stock pile to the bin. Cement is also stored in bins and materials are collected in terms of

weight, weighing by beam scale or spring less dial scale attached to a hopper,

suspended beneath the storage bins.


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Concrete Mixers: Concrete mixers mix the concrete ingredients to make mix of specified

consistency. Mixers are specified by volume of mixed concrete discharged after mixing

of the batch and expressed in cubic meter.

Principal types of concrete mixers are:

Drum Type: these consist of drum and they can be Tilting, Non-tilting orreversing types.

Paving mixer: are used primarily to mix and place concrete for pavements ofhighways, streets and airports. They are mounted on crawler trucks in order that

they may move along with the placing of concrete.

Transit mixers: are the truck units used to supply freshly mixed concrete to a jobsituated away from the site of the central batching and mixing plant. Mixing ofconcrete is done in a mixer attached to a truck.

Handling and Transportation: As soon as concrete is mixed it is transferred from place

of mixing to the site where it is to be placed. In no case this time should exceed the

initial setting time of it. Further it should not cause segregation and should be

economical.

Compaction of Concrete: To insure dense structure free from bubbles compaction of

concrete is done. It can be done by hand or mechanical vibrators. Less vibration do not

produce the required compaction while over vibration causes segregation and bleeding

of concrete.

x) Conveying EquipmentA conveyor is an equipment which is capable of carrying material in a continuous

stream and usually has some kind of an endless chain or belt which by its motion

constitutes the primary device of the conveyor.

xi)Bridge Construction EquipmentPile driving equipment is one of the most used bridge construction equipment, where

the bridge foundation is pile. Timber piles, concrete piles, steel piles and composite

piles are the common ones.

Pile driving equipment consists of pile driving hammers and pile driver and

accessories. For an ordinary hammer:-


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Energy = Weight of ram + Fall of hammer

Pile hammers are rated in terms of m-kg of energy delivered per blow. A heavy ram

impact hammer is working on a short stroke is more effective in driving a pile than a

light ram stroke hammer.

xii)Foundation EquipmentPile driving equipment is single most important foundation equipment used for pile

foundations. For the rest of the works related to foundation works are using the

common construction equipments like excavators, loaders, dump trucks and the like.

A pile driver consists of a device to hold a length of pile in place, hoist to lift it into the

vertical or inclined position and hammer device to provide impact energy required to

drive a pile

xiii) Pneumatic EquipmentPneumatic Equipments are construction equipments used in construction jobs, which

are operated by use of compressed air.

Pneumatic Equipments include; Road Breakers, Jack Hammers, Wagon Drills, Drifters,

Concrete Vibrators. Compressed air is used for various other jobs like spray painting,

conveyors, riveting hammers and grinders.

Compressed air is commonly used because of the following advantages:-

Can be transmitted from one point to another with ease, use of compressed air is safer Pneumatic tools are lighter than other similar ones, Tools using compressed air do not overheat and are cheaper and easy to

maintain.

Air compressor is the most common pneumatic equipment used to increase the

pressure of air by reducing its volume.


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19) Drilling and Blasting Equipment

Drilling and blasting is done before taking up the excavation work. This is commonly

carried out for aggregate production, excavating in tunnels, breaking pavement androcks etc.

Drills in construction are operated either by air or by hydraulics.

Blasting is done to loosen the rock for ease in excavation. Blasting is performed by

discharging the explosive placed in the hole drilled for the purpose.

Blasting is discharging of explosive to loosen the rock,

Explosive is a chemical compound which when burnt under favorable conditions

produces a pressure,

Blasting Powder is a low explosive made from Sulphur, charcoal and sodium orpotassium nitrate. Since it is slow burning are seldom used for rock blasting.

Dynamite is a high explosive with nitroglycerine as the main constituents and are

initiated by a detonator.

20) Shovel and Cranes

Shovels

Shovel family represents rope operated excavators and uses different types of front end

attachments. Followings are the four types front end attachments, by changing themonly, one type of machine is converted into another type, basic structure remain

unchanged.

i) The Dipper or Power Shovel,ii) The Dragline,iii)The Clamshell,iv)The Backhoe or Hoe

Dipper Shovel or Power Shovels are used for digging hard rock in quarries or ore in

mines. These are used for digging above the machine base level, and have faster andmore accurate digging and dumping cycle as compared to dragline, Hoes and

Clamshells.

The power shovel consists of boom, dipper stick, the bucket and the mechanism of

operation.

Dragline operates in such a way it drags the bucket against the material to be dug.

Long light boom of the dragline allows it to dig and dump over long distance as


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compared to a power shovel or Hoe. Therefore it is most suitable for excavation of

channels and cannels can handle wet material and suitable for underwater excavation

while standing away from the pit on a firm soil. Unlike power shovel it can dig

materials below its track level and can handle only softer materials.Clamshell is a machine having most of the characteristics of dragline and crane in

common. Dragging is done like a dragline, once the bucket is filled it works like a crane.

It is very useful for accurate spot dumping of material in a confined space in a vertical

plane. It is used for handling of loose or soft and medium hard materials only.

Hoe is also known as Drag-shovel or pull shovel. Since the digging mechanism

resembles to an ordinary garden hoe, the equipment is named as Hoe. The equipment

has an ability to penetrate even the toughest of materials. Due to this ability these are

commonly used in quarries which have tough digging condition.

Cranes

Cranes have wide application in construction projects, industries and in shipping etc.

These are used for lifting the loads and placing them at desired place. These are

generally electric operated or diesel operated.

The cranes can be classified in the following five classes:

Derrick cranes Mobile crane Overhead crane Traveler crane Tower crane

21) Trenching Dredging and Tunneling Equipment

Trenching is an excavation of trenches for construction purposes. It is an open ditch

type of excavation commonly for laying water, power, sewer and other utility lines.

Dredging means excavation of bed of river, lake or sea for the purpose of deepening.

This excavation is commonly done at docks and harbors to increase the depth of waterway to provide sufficient draft for ships.

Dredger is an equipment used for dredging. Common dredgers used now a days are

Dipper dredger, Ladder dredger, suction dredger and Grapple dredger.

Tunneling in recent years has gained importance in construction industry. This are

required generally for following purposes:


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For underground traffic, Conduit for water, Access to mines,

Conduit for utility services, Subways and underground parking,

Selection of equipment for tunneling depends mainly upon quantum of work involved,

so that tunneling work is carried out economically, speedily and safely.

22) Aggregate Production Equipment

Aggregate of various sizes are required for most of the construction activities.

Production of aggregate involves drilling, blasting, loading, transporting, crushing,

screening, handling and storing.Crushing plants are used to produce aggregates. These crushing plants are fed with the

stones broken from the rocks. The sizes of the stones depend upon the capacity and the

crushing system adopted.

Types of Crushers:

Followings are types of crushers:

i) Jaw Crusher: Jaws crush the stones by compression. The jaw crushers used aseither primary or secondary crushers but are considered best for primary

crushing. These crushers have two jaws, one is fixed jaw and the other is

swing jaw.ii) Impact Crusher: These crushers are used where materials are too hard and

abrasive and finished product requirement is for cubical shape well graded

material. In these types of crusher, stones are broken by means of impact and

not by compression as in jaw crusher. In the impact breaker, stone is normally

fed into the top a breaking chamber and struck by rotating hammers while it

is in suspension. The hammer repeatedly throw the material against breaker

bars forming the roof of the breaker chamber. These are used for primary or

secondary crushing. Since impact is instantaneous, the breaking almost

eliminates the possibility of the development of hidden cracks in the product.This quality is important for aggregate production.

iii)Roller Crusher: The roller crusher is a production crusher, and follows a primarybreaker in the crushing circuit. It is suitable for all types of materials. The

roller crusher can be adjusted to produce a wide range of sizes of material by

changing the discharge opening. The material is fed into the crusher by

means of a feeder discharging into the hopper.


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iv)Cone Crusher: Cone crushers are used to produce the final product, since theycan receive and crush smaller size of stones of ore and produce more fine

aggregates.

Crushing Plants:

Crushing plants are being manufactured by large number of manufacturers all over

the world with capacities up to 1000 tons per hour or so. These plants are either

stationary or portable and changes in the design and construction from

manufacturers to manufacturer and as per job requirement. The crushing plant

employ 2 stages; the primary crushing units are either jaw crusher or impact crusher

and produces the rocks to sizes between 75mm and 250mm, whereas the secondary

units use jaw, impact or cone crushers, in which primary crushed rock is further

reduced to sizes say 5 to 50mm. Materials are transported from the primary unit tothe secondary unit by means of conveyor belts. The secondary unit is equipped with

vibrating screen, return belt conveyors, stockpiling conveyors and chutes.

1.2 General Principles of Equipments

For machine intensive construction projects the equipment cost to performe a particular activity

has to be calculated carefully, so that to estimate the unit price of the individual item. Cost of

equipments are commonly calculated on hourly basis.Determination of equipment cost per hour comprises of:

- Depreciation cost,

- Running cost,

- Owning cost

The owning cost comprises initial costs other than purchasing cost, insyrance costs, and storage

costs.

Once the equipment breakeven costs, which include all costs of equipment owning and operating

costs as well as the cost of operators and overhead costs are determined then profit margin,

which depends entirely on the market competetiveness and company strategies, while income tax

based on tax regulations of the specific country need to be considered to arrive to the final

equipment cost.


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Once the equipment cost per hour is established, be it on rental basis or otherwise, the cost per

unit production or per activity can be determined, provided one knows the equipment production

per a given period.

i.e.

Forexample:

This hand out will deal with how to estimate the productivities of the different equipment in

earth moving operation in the preceding chapters.


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Chapter-2 Planning and Selection of Construction Equipment

Information required to make selection of construction equipments are: Name of

manufacturer, model number, capacity, type, engine type, horse power, speed, dimension

s, operating pressure, type of controls, fuel consumption and weight. These information

are used for evaluation of the bid to purchase the equipment.

Some important issues to be taken into consideration while planning and making a

selection of construction equipments are; downtime cost, obsolescence cost and

depreciation.

Downtime Cost: Downtime is a time that a machine is not under working condition. The

machine is either under repair or adjustment. Hence the productivity of machine decrease

s abd subsequently the production cost per unit increases.

The loss of mony because the machine is not being under use due to downtime is called

downtime cost.

If a machine has an operating cost of 100 birr per hour and downtime is 5%, then

downtime cost per hour is 5 birr. Hence if the machine is used for 2000 hours per year the

n the total downtime cost is 2000x5 = 10,000 birr. Hence there is a loss of birr 10,000 per

year on its production. As the downtime goes on increasing with usage downtime cost

also increases.

Obsolescence Cost: Due to continuos improvements of machines, the production cost per

unit of new machine decreases. This advantage can be gained only by replacing the old

equipment by new improved one. A person who has got this older equipment sustains

loss in the form of decrease in the profit is called obsolescenece cost.


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Average Value of Equipment: Average cost of the equipment is average of the cost of the

equipment in the beginning of first year and nth year. Where n is the useful life of equip

ment.

Consider an equipment has cost (p) on the date of purchase. It is expected that it will have

no salvage after expiry of its useful life.

where, C = Cost of the Equipment

If the Equipment has got salvage value of Vs at the end of useful life of the equipment, the book

value of the equipment in the beginning of nth year will be:

Therefore Average Cost of Equipment (C) equals:-

=

Average annual premium of insurance and taxes are generally calculated on the basis of

average cost of equipment.

Exaples and exercises are to be worked out.

Depreciation: Every asset has got certain useful life. Its biik value goes on decreasingwith time. This decrease in value of an asset with use or age is defined as depreciation. It

is a means of writing off the cost of the asset in a rational and syatematic manner.

The book value of the asset is the difference between the cost of the asset on the data of


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purchasing and the total depreciation made againest asset to that date for which the book

value is to be calculated.

The simplest way of calculating depreciation of an asset is by distributing the depreciatio

n base (original cost of equipment) over its useful life.

2.1 Planning for Construction Equipment

Equipment planning on major construction project besides its relation includes:-

Type of Equipment, Number and size of Machines Type and amount of works to be done, Availability of equipment and its parts and Working shifts

The type of equipment selected depends on types of work, amount of work, soil condition

s and type of material to be handled.

The number and size of equipment depends on amount of work, working days availbale,

number of shifts, availability of labour etc.

2.2 Selection of Construction Equipment

Propoer selection of construction equipment increases the speed of construction and

makes project most economical.

Some general considerations may be made from construction equipment selection are:-

Availability withease, economics should be worked out, Choice should be restricted to standard equipment. Special equipment should be

selected if job justifies its selection,


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Topographical condition, type of soil, access to place etc, Less variety of equipment should be used, Equipments manufactured in own country is prefered, Size of equipment should be according to the amount of work, It is better to use

more than one equipment of small size than using of one of large size.

Obsolescence of equipment, Equipment should be capable of doing more than one job, but it should not be

versatile,

The technical and economical aspects should be analysed,

2.3 Earthmoving Works

Earthmoving is a process of moving soil or rock from one location to another and process

ing it so that it meets construction requirements of location elevation, density, moisture

content and so on.

Activities

The activities involved in earthmoving are:

Excavating, Loading, Hauling, Placing, Compacting, Grading and Finishing

Materials

Soil and rock are materials of interest in construction, when one talks about earthmoving.


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General Soil Charactersitics

Trafficability: is ability of a soil to support the weight of vehicles under repeated traffic

load. When poor trafiicability condition exists, propoer drainage, stabilization of haul

routes or the use of low grounds - pressure construction equipment may be required

Loadability: is measure of the difficulty in excavating and loading a soil

Soil Volume Change Characteristics

Bank: Material is in its natural state before disturbance. Itsunit volume is identified as

bank cubic meter (Bm3).

Loose: material has been excavated or loaded. Its unit volume is identified as loose cubic

meter (Lm3).

Compacted: material after compaction. Its unit volume is identified as a compacted cubic

meter (Cm3)

Swell

Swell is an increase in volume of soil due to excavation. During excavation unit bank

volume is changed (Bank Density) as a result of swelling.

Swell is an expression of relationship between Bank and Loose (excavated) volume.

L= L=


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B= Bv=

Swell (%) = [ 100

Shrinkage

Shrinkage is a result of compaction and is the reverse of swelling.

Shirinkage is an expression of relationship between Bank and Compacted soil volume.

NB:BothSwellandShrinkagearecalculatedagainstBankVolume

Load and Shrinkage Factors

In performing earthmoving calculations it is more apropriate to convert all volumes into a

common unit of measurement. (one of VL, VB, VC). To simplify the computation it is

good to have a conversion factor. These factors are called Load Factor and Shrinkage

Factor.

A Pay meter is that volume unit which is used as a basis of payment in contract.

Load Factor:


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But

Spoil Banks

If a pile of excavated material is long when compared to its width it is called spoil bank,

but if it is dumped from a fined position a spoil pile is created. Spoil Bank is excavted

material while Spoil Pile is Dumped.

=AngleofRepose

L>B

H

B

L


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Conical Spoil Pile

H

D

H=D/2*tan

V= D3tan/24

D3

=24V/tan


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Chapter - 3

Production and Job Management of Construction Equipment

The aim of project management is to make the project cost effective as much as possible.

If the cist is not competent the project cost becomes too high to win the bid. Therefore

production estimate of equipments and job management is necessary in the construction

projects.

1. Earthmoving Equipments

The production of earthmoving equipment can be estimated by:

Production = Volume per cycle * Cycle per hour

Cycle per hour include all appropriate efficiency factors, so that it represents the number

of cycles actually achieved (expected to be achieved) per hour. Usually manufactureres

provide charts on table.

Cycle per hour can be determined by:

a) number of effective working minutes per hour,

b) multiplying the number of theorotical cycle per hour by a numerical efficiency factor

as follows:-

Job Condition Management Condition

Excellent Good Fair Poor

Excellent 0.84 0.81 0.76 0.70

Good 0.78 0.75 0.71 0.65

Fair 0.72 0.69 0.65 0.60

Poor 0.63 0.61 0.57 0.52


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management condition includes:-

- Skill, training and motivation of workers,

- Selection, operation and maintenance of Equipments,

- Planning job layout, supervision and condition of work

Job condition includes:-

- Topography and work dimension,

- Surface and weather condition,

- Specification requirement,

Exercice-1

Observation indicate that an excavation carries an average bucket load of 1.5 Lm3 per

cycle. Cycle time average 1 minute. Job conditions are rated as good and management

condition as fair. Estimate the hourly production in Lm3 for this operation.

Exercise-2

The hourly cost of a shovel is Birr 36 and of a truck is Birr 16. If an equipment fleet

consisting of one shovel and eight trucks achieve a production of 141 Bm3/hr, what is the

unit production cost?

Exercise-3

A soil weighs 1282 kg/m3 loose, 1602 kg/m3 in place and 1842 kg/m3 compacted. Find

the swell and shrinkage of this soil and if a scraper has a heaped volume capacity of 33.6

m3, calculate how many Bm3 of soil the scraper can carr

2 Excavating and Lifting Equipments


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These includes mainly:-

- Crane - Shovel family (shovels, draglines, hoes and calm shells)

- Dozers,

- Loaders,

- Scrapers

i) Excavator Production

In order to estimate production of an excavtor first the volume of material actually

contained in bucket load should be determined.

Machine Rated Bucket Capacity

Back hoe Struck volume

Clamshell plate line or water line capacity

Dragline 90% of struck volume

Loader Heaped Capacity at 2:1 angle of repose

Shovel Stuck volume

Struck Volume: when the load is struck or flush with the bucket sides,

Plateline Capacity: bucket volume in a bucket following the outline of the bucket sides,

Water Line: level that would result of the bucket if filled with water,

Heaped Volume: maximum volume that can be heaped without spillage at a given

diameter.

To make a better estimate of the volume of material in one bucket a bucket fill factor or

bucket efficiency factor is considered. Otherwise one can assume heaping on buckets to

take care of swelling of soil in bank state.


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Exercise-1

Estimate the bucket load for a loader whose heaped capacity is 3.82 m3. The soils bucket

fill factor is 0.9 and its load factor is 0.8

3 Crane - Shovel Family

The crane - shovel family consists of three major assembles:-

- a carrier or a mounting,

- a revolving super structure containing the power and control units (turn tables)

- a front and attachement

i) Shovels

A cable operated shovel digs with a conbination of a crowed action and a hoist action.

Eventhough a shovel has a limited ability to dig below track level, it is very efficiet when

digging from track level to about the height of the shipper shaft.

The vertical distance that permits the bucket to obtain a full load without undue crowding

or hoisting is known as the optimum deth of cut.This depth depends on shovel size, angle of swing and height of bank, types of soil to be

excavted and overall jpb efficiency.

The shovel must have a vertical surface againset for effective digging. This digging face

is earily formed when excavating a bank or a hillside.

Best application of shovel is when digging of enbankment is on one side and dumping or

loading on the other side.

Shovel production

The production of a shovel is calculated as:

Actual Production = Ideal output * Swing-depth factor * Efficiency


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The ideal output and the swing depth factot are determined from tables of manufactirers.

The efficiency is determined from job and mangement conditions. It is sometimes

appropriate to multiply the result by bucket laod factor in case loose volume is used.

Actual Production = [Ideal Output][Swing Depth Factor]x[Efficiency][Bucket Load Fa

ctor]

Exercise

Determine the expected shovel production of "diesel powered cable operated shovel" in

bank cubic meters per hour for the following condition:

Shovel size = 1.53 m3Swing angle = 120 m3

Average depth of cut = 2.5 m3

Material = Common earth

Job & Management conditions are good

Job Management

The two major factors controlling shovel production are the swing angle and lost time

during the production cycle.

Therefore the angle of swing between digging and dumping should always be kept to a

minimum. Haul units must be positioned to minimize the cost as units enter and leave the

loading position. When only single loading position is available the shovel operator

should utilize the time between the departure of one haul unit and the arrival of the next

to move up the digging face and to smooth the excavation area. The floor of the cut

shovel be kept smooth to provide an even footing for the shovel and to facilitate moveme

nt in the cut area. The shovel should be mobed frequently to keep it at optimum distance

for the working face. Keeping dipper teeth sharp will also increase production.


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Other Applications are:-

- Dressing slope,

- Making its own Road way,

- For very shallow trenches

- etc

ii) Draglines

The Dragline is a very versatile machine that has the longest reach for digging and dump

ing of any member of the crane-shovel family. But it doesn't have the positive digging

action or lateral control of the shovel. Hence the bucket may bounce or move side way

during hard digging.

Production Estimate

Estimated Production = Ideal output * Swing depth factor * Efficiency

Exercise-1

Determine the expected dragline production in Lm3 per hour based on the following data:

- Dragline size = 1.53 m3

- Swing angle = 1200

- Average depth of cut = 2.5m

- Material = common earth

- Job management condition is good

- Alternatively job efficiency factor = 50 min/hr


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Job Management

Trial operations may be necessary to select boom length, boom angle, bucket size and we

ight and the attachement position of the drag chain that yeild maximum production.

As shovel operation maximum production is obtained with a minimum swing angle.

iii) Back Hoes

This is an excavator designed primarly for excavtion below ground (below ground level).

The backhoe is widely utilized for trenching work. It can also perform laying pipe

bedding placing pipe trenching work. backfilling etc.

In trench excavation the best measure of production is the length of trench excavated per

unit time.

Production Estimate

Production [Lm3/hr] = C*S*V*B*E

Where:C = Cycle/hr S = Swing depth factor V = Heaped bucket volume (Lm3)

B = Bucket fill factor E = Job efficiency

In trench excavation a fall in factor (adjustment factor) should also be considered for

materials that fall back.


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Standard Cycle per hour for hydraulic

Type of Material Machine Size

Wheel Tractor Small Excavator

(0.76m3 or less)

Medium

(0.74 - 1.72 m3)

Large

(>1.72m3)

Soft (Sand, Gravel

Loam0

170 250 200 150

Average (common

earth, soft clay)

135 200 160 120

Hard (tough clay

rock)

110 160 130 100

Depth of cut

(% of optimum)

Swing depth factor

Angle of Swing

45 60 75 90 120 180

30 1.33 1.26 1.21 1.15 1.08 0.95

50 1.28 1.21 1.16 1.10 1.03 0.91

70 1.16 1.10 1.05 1.00 0.94 0.83

90 1.04 1.00 0.95 0.90 0.85 0.75

Adjustment factor for trench excavation production

Type of Material Adhjustmnent Factor

Soft 0.60 - 0.70

Avergae 0.90 - 0.95

Hard 0.95 - 1.00

Exercise - 1

Find the expected production in Lm3 per hour of a small hydraulic excavator. Heaped

bucket capacity is 0.57 m3. The material is sand and gravel with a bucket fill factor of


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0.95. Job efficiency is 50 min/hr. Average depth of cut is 4.3m. Maximum depth of cut is

6.1m and average swing = 900.

Job Management

In selecting a proper backhoes for a project consideration must be given to the maximum

depth, working radius and dumping height required. Check also for the adequate

clearance of the carrier, superstructure and the boom during operation.

Also the backhoe will excavate fairly hard material, don't use the backet as the sladge in

attempting to fructure rock. Light blasting or use of a power hammer may be necessary to

loosen rock sufficiently for excavation. When lifting pipe don't exceed load given in themanufacturers safe capacity chart for the suituation.

iv) Clam shells

When the crane shovel family is equipped with a crane boom and clam shell bucket, it be

comes an excavator known as clamshell.

Clam shells are commonly used for excavating bulk material from rail, cars and ships and

moving bulck material from stock piles.

Production Estimate

The production estimate is based on the equation:

Production = Volume per Cycle * Cycle per hour

Exercise - 1

Estimate the production Lm3 per hour for a medium weight clam shell excavating loose

Earth. Heaped bucket capacity = 0.75 m3. The soil is commomearth with a bucket fill


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factor of 0.95. Estimated cycle time is 40 seconds. Job efficiency is 50 min/hr.

Job Management

The maximum allowable load (bucket weight plus soil weight) on a clam shell should be

obtained from the manufacturer Clam Shell Loading Chart. If a Clam Shell loading chart

is not available, limit the load to 80% of the safe lifting capacity given by the crane

(boom) Capacity Chart for rubber tyred equipment or 90% for crawler mounted

equipment. Cycle time i reduced by organizing the job so that the dumping radius is the

same as the digging radius. Keep the machine level to avoid swinging appel or down

wheel.

v) Cranes

Cranes are primerly used for lifting, lowering and transporting loads. Cranes are of

different types:-

a) Mobile cranes: consisting of a crane shovel carrier and superstructure equipped

with a boom and hook.

b) Hydraulically operated equipment: with hydraulically powered telescoping boom

cranes (up to 24 stories) (ex. KATO crane).

c) Tower Crane: are widely used on Buildings and Construction Projects because of it

wide operating radius ued unlimited height capacity.

The main factors that controls the load that may safely be lifted by a tower crane is its

operating radius (distance from center of rotation to the hook).

For the other cranes this is function of the boom length anf boom angle above the

horizontal.


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Crane manufacturers provide charts giving the safe lifting capacity as a function of boom

length, boom angle and position of boom with respect to the carrier. Other factor to be

taken into consideration is the amount of counter weight and condition of supporting

surface.

Job Management

There are a number of attachments besides the hook available to assist the crane in lifting

and transporting various types of loads. Among these concrete buckets, slings and special

hooks are most often used in construction applications. Crane accidents occure

frequently in construction works, particularly when lifting near capacity loads and when

operating with long booms.Some suggestions for safe crane operation includes:-

a) Use a communication system or hand signs when the operator can not see the load

at all time. Make sure that all workers involved in the operation know the hand sign

s to be used.

b) Provide tag lines or restraining lines when there is any danger due to swinging load

s and etc.

4. Compacting and Finishing

i) Compaction

Compaction is a process of increasing the density of the soil by mechanical forcing the so

il particles closer together, thereby expelling air from the void spaces.

Consolidation is an increase in soil density resulting from expulsion of water from the

soils void spaces.

The degree of compaction depends on:-

- Soils physical and chemical properties,- Soils moisture content,- Method of compaction,


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- Amount of compactive efforts,- Thickness of soil layer being compacted (lift thickness),

The basic compaction forces are:-

- Static weight,- Impact (good for plastic soils)- Vibration (good for cohesive soils)

Types of Compaction EquipmentsTamping Foot Rollers: This utilizes a compacting drum with a protruding feet. Exaple

Sheep foot rollers

Vibratory Compactors: These range from small hand operated compactor to rollers.

Example; Vibratory plate compactor and vibratory tamping foot compactor.

Steel wheel or smooth drum rollers:

Tampers or Rammers: small impact type compactors which are primarly used for

compaction in confined areas.

Estimating Compactors Production

Based on the compctors speed lift thickness and effective width of compaction the follow

ing formula can be used to estimate compactor production:

Where: P = Number of passes required


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W = Width of compaction per pass (m)

S = Compactor speed (Km/hr)

L = Lift thickness (cm)

E = Job efficiency

Typical Operating Speed of Compactor

Compactor Speed (km/hr)

Tamping foot, crawler towed 5 - 8

Tamping foot, wheel towed 8 - 16

High speed tamping foot

- First two or three passes

- Walking out

- Final Passes

5 - 8

13 - 19

16 - 23

Smooth wheel 3 - 6

Vibratory

- Plate

- Roller

1 - 2

2 - 3

The speed and the lift thickness are the most important factors which advesly affect the

production and must be estimated carefully. Usually trial operations are carried out to

determine L & S. In making trial operation it is usually required to determine the exact

values of soil moisture content, lift thickness and roller weight that yields maximum

production for achieving the specified soil density.

5. Grading and Finishing

Grading is a process of bringing earth work to the desired shape and grade. Its finishing

involves, smoothing slopes, shaping ditches and bring the earth work to the elevation

required by the plans and specification. Balancing is the process of cutting down high

spots and filling in lowspots of each road way layers. Trimming is a process of bringing


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each road-way to its final grade.

Motor Grader

A motor grader is an equipment used for grading and finishing. The blade of a motor

grader is called a mold board and is equipped with replacible cutting edge and end pieces.

It has a wide range possible positions as in Bull Dozers. Graders are available with auto

matic grade control system that permits precise grade control.

Grade Excavators & Triming

These are machines that are capable of finishingroad way and air field subgrades & bases

faster and more accurately than motor graders. They are capable of removing soil andold asphalt pavements. They are equipped with integral belt conveyors that are used for

loading into haul units or depositing outside the excavated area.

Estimating Grader Production

It is computed on a linear basis completed per hour for road ways and on area basis for ge

neral construction products.

The time required to complete a road way may be estimated by:-

Average speed depends on operator skill, job condition etc. The follwing can be used in

the calculation:

Operation Speed (km/hr)

Bank sloping 4.0

Ditching 4.0 - 6.4

Finishing 6.5 - 14.05

Grading & Road Maintenance 6.4 - 9.7


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Exercise - 1

A 24.1 km of gravel road requires reshaping and leveling.

Estimated number of passes is 6 with 2 passes @ 6.4 km/hr; with 2 passes @ 8.0 km/hr

and with 2 passes @ 9.7 km/hr where the Job efficiency is 0.80.

How much grader hours will be required?

Job Management

Careful job planning use of skilled operator and competant supervision is required to max

imize grader production. For distance less than 300 meter, have the grader back rather than to turn around.


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Chapter-4 Equipment Management

4.1 Equipment Management in Construction Projects

4.2 Economics of Construction Equipment

4.3 Safety and Insurances

4.1 Equipment Management in Construction Projects

The cost of equipment in a project varies from 10 to 30% of the total cost of the projectdepending on the extent of mechanization. Proper planning, selection, procurement,

installation, operation maintenance and equipment replacement policy plays an important

role in equipment management for the successful completion of the project.

Equipment manager's main task is to reduce downtime, achieve optimum equipment

utlization and increase production at minimum cost. The cost analysis and the will of

adopting proper techniques suited to the situation are the basic factors for the success and

therefore, there is a need for a rational planning, proper selection and judicious

deployment of equipment in relation to the condition so as to achieve optimum

utilization. Equipment management integrates and continously interacts with human,

technical, and production system in order to achieve top efficiency and cost effectiveness.

Purchase of Equipment

Once the selection of the equipment is done the purchase order for the selected model and

type is issued considering lead time for the supply of equipment, time required for

installation and commissioning and the time when the equipment should be available for

use.

The complete procurement action is divided in various activities like calling enquiries,

its technical and financial evaluation, ordering, contract making, transporting,


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assembling and installation and commissioning and should be followed vigorously, as

any delay in any of these avtivities will result in delay in completion of the project.

Therefore these activities are monitored at top most priority.

Generally fast moving or maintenace spares are purchased along with the equipment

specially for the period of one or two years. Equipment should be purchased in phases, so

that the money is not blocked and equipments required later do not remain idle.

Purchasing v/s Hiring

The decision whether to purchase or acquire by hiring should be in favour of the sources

which is more economical.

Points in favour of purche are:

- when the equipment is likely to complete its useful life at the end of the project,- remains available for use whenever it is needed,- purchased equipment is kept in better condition and relaible,

Points in favour of Hire (againest owning) are:

- possible danger of obscelence,- when the equipment requires huge initial investment,- when the equipment can not be used for its full life,

4.2 Economics of Construction EQuipment

Economics of construction equipment deals with the study of working of the equipment

to compute the unit costs of production. Unit cost of production is calculated after estimat

ing the cost of production by calculating hourly ownership and operating cost of the

equipment and knowing hourly production of that equipment.


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Equipment selection is a decision making from various alternatives which gives least cost

of unit production. It should consider the rate of interest on the equipment, time required

to complete the project and effect of time on the project, as we know that time is money.

Hourly Working Rate: Hourly working rate of construction equipment comprises of the

following components: (i) Owning Cost and )ii) Operating Costs.

Owning Cost is made up of investment cost, deprciation cost and major repair cost.

Operating Costs includes cost of fuel, cost of lubricants, servicing and maintenance cost,

labor cost, cost of field repairs and various other overheads.

4.3 Safety and Insurance

Millions of industrial accidents occure every year. In these accidents a lot of workeres

lose their lives every year in the world. Accidents may cause injury which sometimes

result in death or permanent total displacement. Statistics shows that 98% accidents can

be avioded and only 2% can not be pre-assessed. Accident can not be expressed in money

terms only. It also affects individuals and his family.

Losses Due to Accidents

Losses due to accident are either direct or indirect losses.

Direct losses are the losses due to the employer, which he pays to the workers for

compensation. Employer also pays for medical expenses incurred on the worker. These

type of losses can be measured in terms of money.

Indirect losses arise from the following sources:

- Loss of time of his injured person,- Loss of time of his fellow workers, who stop work at the time of accident to help

him,

- Loss of time of supervisors in assisting, investigating, making alternativearrangements and selecting and training new workers to fill the vacancy,


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- Loss caused due to damage caused to the machine,- Loss due to reduction in the efficiency of workers after recovery,- Loss due to reduction in the efficiency of fellow workers due to fall in their moral,- Loss to the injured worker; his income, medical expenses and pain felt.

Engineering Insurances

The engineering insurance covers may be machinery erection insurance or machinery

breakdown insurances.

The followings are relevant engineering insurances:

-

Contractors all risks insurance- Machinery breakdown insurance- Loss of profit insurance following machinery breakdown and- Contractor plant and machinery insurance

Contractors all risk insurance (CAR)

This provides insurance on all risks i.e. on almost any sudden and unforseen loss or

damage occuring to the property insured. These include, fire, explosion, flood, rain, wind,

storm, snow, earthquake, teft, bad workmanship, lack of skill, war, negligence,

radiation, penality losses, repair etc.

Machinery Breakdown Insurance

Breakdown cover is offered to all type of installed machinery working in fixed premises.

The cover can be extended to include damage to third party.

Loss of Profits Insurance Following Machinery Breakdown or Machinery Loss of Profits

Policy

Some times when a small but vital part of a machine fails, entire work comes to a stand

still. In these circumstances this insurance policy covers the consequential losses that

may be suffered by the machine user following a breakdown.

Contractors Plant and Machinery Insurance

Construction machinery are now-a-days insured under the contractors plant and


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machinery (CPM) insurance policy, which is annual policy, providing insurance againest

Loss due to Overturning, Act of God, Riot, Strike and Theft.

This insurance doesn't cover losses arising due to electric or mechanical breakdown,

normal wear and tear and negligence.

Documents

Cons Eqt Handout 2