ORDNANCE FACTORY BOARD

Indian Ordnance Factories is a giant industrial setup working under the Department of Defense Production of the Ministry of Defense. Indian Ordnance Factories , headquartered at Kolkata is a conglomerate of 39 factories, 9 Training Institutes, 3 Regional Marketing Centers and 4 Regional Controller of Safety.

FUNCTION OF OFB

Function of OFB with its 39 factories is to provide A broad and versatile production with multi-technology

capacities State of the art manufacturing facilities Large reservoir of skilled and professionally qualified manpower

and managerial personnel Strict adherence to quality standard ( all units are ISO 9000

certified) Original as well as adaptive research & development to make

need based refinement and modifications Project engineering capability A strong base for industrial training facilities Ready market access due to location

PRODUCT RANGE

Items produced in the ordinance factories are highly sophisticated and complex in nature. These include following items :-

Pistol/Revolver Civilian Arms & Ammunition Weapons Ammunition, Explosives, Propellants & Chemicals Military Vehicles

Armored Vehicles Optical Devices Parachutes Support Equipment Troop Comfort & General Stores Material, Components & SPMs

CUSTOMERS

The prime customers of Indian Ordnance Factories are the Indian Armed Forces. Apart from supplying armaments to the Armed Forces, Ordnance Factories also meet the requirement of other customers viz. Central Paramilitary Forces and State Police Forces in respect of Arms, Ammunition, Clothing’s, Bullets Proof Vehicles and Mine Protected Vehicles etc.

Increase in volume of export, as an extension to its’ functioning remains an important objective of Ordnance Factories.

GREY IRON FOUNDRY, JABALPUR

Grey Iron Foundry ( GIF ), Jabalpur was set up for production of automobile castings of Grey Iron & Malleable Iron required for Shaktiman & Nissan Vehicles produced at Vehicle Factory, Jabalpur & Vijayanta Tanks produced at Heavy Vehicles Factory, Avadi. The factory was commissioned in technical collaboration with SKODA, Czechoslovakia under an agreement on economic co-operation with Govt. of India & Govt. of Czechoslovakia. The production commenced from July 1976. Due to phasing out of Nissan, Shaktiman vehicles & Vijayanta Tank, GIF has entered Civil Trade market & diversified its production towards Ammunition items & Ammunition Boxes, in addition to supplying castings to VFJ for LPTA & Stallion vehicles.

Grey Iron Foundry is located adjacent to Vehicle Factory, Jabalpur on eastern side of main Jabalpur – Allahabad railway line at a distance of 9 Km. from Jabalpur Railway Station.

Construction of factory was started in May 1970 on an area of 21.99 Hectare. The total covered area is 45,590 Sq. Mt.

PRODUCT RANGE

a) Product range comprises of :-

Grey Iron Castings of four grades i.e. FG – 150, FG – 200, FG – 260, FG – 350 to IS : 210 – 1993 Spheroidal Iron Castings of grade 400/12, 450/10, 500/7, 800/2, 900/2 to IS : 1865 1991, Steel Castings (Weight of individual castings varies between 350 gm to 285 Kg )

b) GIF has taken up the development of castings for Ammunition items of 100/120 Kg., 250 Kg, 450 Kg, and 1000 lb. Bomb Body etc. and Ammunition Boxes of C43A, C44A, C48A, C51A, C53A, H2A, H5A, Carrier 6AL& Carrier 13AL. etc..

MODERNIZATION PLAN AND PROGRESS ON IMPLEMENTATION

GIF has conceived a modernization scheme to effect technical up gradation in the area of Sand Preparation, Melting Technology with simultaneous improvement in productivity & quality characteristics of the product to keep pace with the modern foundry in the country. Major plants and machinery covered under the envisaged scheme and planned to be procured within the 11th and 10th Plan Period under Modernization Scheme are:

1) Two sets of 3 ton Medium frequency Induction Furnace has been commissioned and put into regular production line and

2) Two sets of Turbo mixer types Sand Mixer/Mullers have been commissioned and put into regular production line.

3) CNCs like SBCNC-30, two sets of Fanuc -OT

G.I.F has following shops:-1) Foundry Shop2) Melting Shop3) Core Shop

4) Pattern Shop5) Fettling Shop6) EM Shop7) Compressor Shop8) Spectrometer lab 9) CNC Centre

PATTERN SHOP

Pattern is the principle tool during the casting process. It is defined as the model of anything, so constructed that it may be used for forming an impression called mould in damp sand or other suitable material. When the mould is filled with molten metal, and the metal is allowed to solidify, it forms a reproduction of the pattern and is known as casting. The process of making pattern is known as pattern making.

Pattern making material should be:1) Easily worked, shaped and joined.2) Light in weight3) Strong , hard and durable4) Dimensionally suitable in all situations5) Low cost

6) Repairable7) With good surface finish

Selection of pattern material should depend primarily on the following factors:

1) Service requirement2) Type of casting and moulding process3) Possibility of design changes

Common materials used in casting process are:

1)Wood: Wood is the most common material used for casting. It is easy to work with and it is readily available. It can be fabricated to any shape by gluing. It can be sanded to a smooth surface.

2)Cast Iron is used in highly specialized patterns. It is strong ,gives a good smooth surface with sharp edges and is resistant to the abrasive action of the sand.

3)Aluminum: Aluminum is a good material for casting as it melts at relatively low temperature, is soft and easy to work with, light in weight and resistant to corrosion. Aluminum being soft is liable to damage by the rough usage.

4)Thermocol : Thermocol are used for one time patterns which require very high finish and have very much complex shape. When molten metal is poured over the thermocol it gasifies due to heat.

TYPES OF PATTERN

Patterns are of basic types, each satisfying certain casting requirements.

1. Single piece pattern2. Split or two piece pattern3. Match plate pattern

Single Piece Pattern

The one piece or single pattern is the most inexpensive of all types of patterns. This type of pattern is used only in cases where the job is very simple and does not create any withdrawal problems. It is also used for application in very small-scale production or in prototype development. This type of pattern is expected to be entirely in the drag and one of the surface is is expected to be flat which is used as the parting plane. A gating system is made in the mold by cutting sand with the help of sand tools. If no such flat surface exists, the molding becomes complicated.

A Single Piece Pattern

Cope and Drag /Two Piece Pattern

Split or two piece pattern is most widely used type of pattern for intricate castings. It is split along the parting surface, the position of which is determined by the shape of the casting. One half of the pattern is molded in drag and the other half in cope. The two halves of the pattern must be aligned properly by making use of the dowel pins, which are fitted, to the cope half of the pattern. These dowel pins match with the precisely made holes in the drag half of the pattern.

A Two Piece Pattern

Match Plate Pattern

When split patterns are mounted with one half on one side of a plate and the other half directly opposite on the other half directly opposite on the other side of the plate, the pattern is called a match plate pattern.

Other types of pattern are:-

Gated Pattern Loose Piece Pattern

Sweep Pattern Sweep Pattern

Boxed-up Pattern Shell Pattern

Skeleton Pattern Lagged up Pattern

PREPRATION OF PATTERNS

Layouts and template are the reproduction on the blueprints laid out to full size scale on a flat smooth wooden board. Blue-prints are made by blackening the board and then making drawings with chalk.

After making pattern layout, necessary allowances are added like shrinkage, draft, machine, finish allowances.

Next step comes the shaping of pieces to construct the pattern

The particular method used for making pattern depend upon the size and shape of the pattern and the number of castings to be made.

The permanent patterns are made by Araldite (SW-404) 100gm and Hardener (HY-2404) 10 gm. Filler , gel and lamination are added to make permanent castings.

GREEN SAND

High silica sand having grade IS-197 grade- 425 is used in making green sand mould.

Composition of green sand mould is-

1) Silica (SiO2) - 98%2) Moisture - 3% max3) Clay - 2% max

a) Sand Grade : Coarse Sand more than 8% Medium Sand more than 75% Fine Sand 3% Moisture 0.5%

b) Bentonite is the binder material added in sand. 90% pass through 75 um sieve 98 % pass through 150 um sievec) Gel should have a gel index of 55ml/min and moisture content 6-12 %

d) Coal dust having 20% maximum ash and 3% moisture.

e) Dextrin is creamed colored fine powder

100% pass through 150 um

Core and Core Print

Castings are often required to have holes, recesses, etc. of various sizes and shapes. These impressions can be obtained by using cores. So where coring is required, provision should be made to support the core inside the mold cavity. Core prints are used to serve this purpose.

The core print is an added projection on the pattern and it forms a seat in the mold on which the sand core rests during pouring of the mold. The core print must be of adequate size and shape so that it can support the weight of the core during the casting operation. Depending upon the requirement a core can be placed horizontal, vertical and can be hanged inside the mold cavity.

Carbon Dioxide Moulding

This process is basically used for moulds and cores.The principle is based on the fact that CO2 gas is passed through a sand mix containing sodium silicate become stiff gel. The gel is responsible for necessary strength to the mould. The sand used for the process should dry with a maximum moisture content 0.25% and free of clay. When the packing is complete, CO2 is forced into the mould at a pressure of about 1.4.5kN/m2. The time taken to harden the medium size body is 15 to 30 sec. The hardness can be further increased by exposing them to the free atmosphere for a short while after gassing.

CNC Centre

CNC shop has some of highly sophisticated CNC machines and it used for those jobs which require high accuracy and finish.

There are some of the most advanced CNC used in GIF CNC centre for faster and accurate work. Following CNC machines are present at GIF:

1) Two set of CNC FANUC –OT

FANUC -OT2) A Vertical CNC Centre3) A Centre Lathe Machine4) Two SBCNC-30

SBCNC-30

CNC centre is under Modernization Scheme and is likely to have more high-tech CNCs in coming months.

Jobs prepared in CNC shop are-

a) Plug Liftb) Head for Arial Bomb(100/120 kg)c) Hand Grenade Bodyd) Base Adapter Bushe) Nose Adapter Bushf) Adapter Bushg) Cylinder for Arial Bombh) Bush of Base Booster Casing

Grenade

Arial Bomb

CNC PROGRAMMING

The most basic method is to simply do the necessary geometric calculations with a calculator and write the program directly using G-codes, M-codes, and so on. The program is then keyed directly into the controller (usually called MDI, for Manual Data Input) or keyed into a computer and transferred to the controller via punched tape or some other medium.

The CNC machine manufacturer often adds their own operation panel with all the button and switches needed to operate the CNC machine and all its features.

Control unit have two basic components:1) Operation Panel is full of rotary switches, toggle switches and

push buttons.2) Display screen with keypad

A typical Operating Panel of the CNC Machine

CNC Programs are the instruction codes which give step by step instructions to the CNC machine to perform any operation.

Memory CNC programs can be stored in the control memory.

Manual Program Intereruption If in a program is to be interrupted in the middle of processing, the control system offers ways to do that using the machine operating panel.

The most common features of this type are toggle switches or push buttons for a single block operation, feedhold and emergency stop.MDI (Manual Data Input) During setup, the CNC operator has to do a number of physical movements of machine slide, spindle rotation, tool change etc. So in order to operate CNC with the conventional devices the system offers a feature called as MDI. MDI enables the input of the program data into the system on program instruction at a time.

Some functions of Operating Panel

G-Codes

G-Code is one of a number of computer code languages that are used to instruct CNC machining devices what motions they need to perform such as work coordinates, canned cycles, and multiple repetitive cycles. Industry has standardized on G-Code as its basic set of CNC machine codes.

G Code List

G0 rapid positioning  G1 linear interpolation  G2 circular/helical interpolation (clockwise)  G3 circular/helical interpolation (c-clockwise)  G4 dwell  G10 coordinate system origin setting  G17 xy plane selection  G18 xz plane selection  G19 yz plane selection  G20 inch system selection  G21 millimeter system selection  G40 cancel cutter diameter compensation  G41 start cutter diameter compensation left  G42 start cutter diameter compensation right  G43 tool length offset (plus)  G49 cancel tool length offset  G53 motion in machine coordinate system  G54 use preset work coordinate system 1  G55 use preset work coordinate system 2  G56 use preset work coordinate system 3  G57 use preset work coordinate system 4

G58 use preset work coordinate system 5  G59 use preset work coordinate system 6  G59.1 use preset work coordinate system 7  G59.2 use preset work coordinate system 8  G59.3 use preset work coordinate system 9  G80 cancel motion mode (includes canned)  G81 drilling canned cycle  G82 drilling with dwell canned cycle  G83 chip-breaking drilling canned cycle  G84 right hand tapping canned cycle  G85 boring, no dwell, feed out canned cycle  G86 boring, spindle stop, rapid out canned  G87 back boring canned cycle  G88 boring, spindle stop, manual out canned  G89 boring, dwell, feed out canned cycle  G90 absolute distance mode  G91 incremental distance mode  G92 offset coordinate systems  G92.2 cancel offset coordinate systems  G93 inverse time feed mode  G94 feed per minute mode  G98 initial level return in canned cycles

LABORATORY FOR FERROUS MATERIAL

There are Physical laboratory for testing of physical properties of metal casting and products and Spectro laboratory for Spectro analysis of ferrous material.

Spectrometer Lab have sophisticated equipments in operation. There is arrangement include Vacuum direct Emission Spectrometer , Eltra C-S Determinater and Leco Apparatus. A rocket system is attached from different furnaces to the lab for instant dispatch of test sample.

DIRECT READING VACUUM EMISSION SPECRTOMETER

Direct Reading Vacuum Emission Spectrometer

Spectrometer is used for spectro-chemical analysis of soild ferrous material. The spectrometer gives result in 10 to 20 seconds. It is ISO certified and it’s testing can be cross referenced from Q.M. Section QM-8.24 , Q.P.-018, ASTM-E-415 and IS-8811-1998.

Spectrometer primarily is useful for:-

1) Instant and accurate on line monitoring of the chemistry of samples at various stages of melting

2)Testing of product samples to conform to specification before dispatch 3)Testing of raw materials 4) Testing of samples for customers

Principle of operation: A stable fully digitalized plasma Spark/Arc is generated in the gap between the sample surface and a tungsten electrode tip in an argon atmosphere as exciting medium. The light produced is separated in to its componentwavelengths with a holographic grating of 3000-4000 grooves/mm. The spectral lines obtained spread on the circumference of a circle called Rowland circle. The light intensity is converted to electric charge by sensitive Photo multiplier tubes Photo multiplier tubes &CCD, amplified , measured and converted into percentage composition, incorporate necessary inter element corrections (additive, multiplicative & matrix corrector) using suitable electronics, software and hardware. It should display and print out accurate analysis of all elements simultaneously, within less than 10 Sec. An average of three identical results is considered as final accurate result. An effective type calibration/ Type standardization

program must be able to do automatic correction of the results with respect to a reference standard of identical chemistry . The system must be able to analyze accurately & quantitatively all the elements, ranges & grades mentioned in the annexure-2 & 3 respectively.

The System must have following facilities features and specifications:

SPECTROMETER: Consist of: 1)Optics 2)Source 3)Spark Chamber 4)Argon system 5)Electronics 6)Accessories 7) Computer, Printer, Hardware & Software , Furniture & Peripherals.

1) OPTICS: (Vacuum Optics is not preferred in view of possible contamination of

optics with vacuum pump oil/Oil fumes which cause deterioration of intensity & deterioration of performance of the spectrometer. Multiple -Optics design is prefered for ease of maintenance and for best selection of spectral lines to avoid complicated inter element interferences, It consists of precision entrance slits , High resolution Hollow graphic grat ing of 3000-4000 grooves/mm, 2000-3000 grooves/mm or its combination. The UV light path must be optimized for maximum intensity, Detectors must be Photo multiplier tubes/ Photo multiplier tubes &CCD of-selected spectral sensitivity for covering ranges of concentration levels ,Prefered Rowland circle of diameter 750mm and Paschen-Runge mounting. Select ion of spectral lines must be preferably first order. The optical resolution must be minimum 9 pico meters. Optics must be stable &the effect of surrounding temperature must be minimum. Temperature stabilized design should ensure frequency of profiling to a minimum-ones in 3months or less. Provision for easy , fast automatic computer controlled profiling for accurate alignment of spectral lines. It must cover a wave length range of approximately 11Onm-BOO nm, in order to accurately determine, Nitrogen, trace elements, moderate elements & High concentration elements. The UV optics must be filled with High Purity inert gas and purified continuously, in order to eliminate traces of Oxygen & moisture. The elements in visible region must be arranged in multiple (2 to 3) air optic. The light path for Air optic is through specia lly designed optical fibres for reducing reflect ion/refraction loss. Necessary Stray light protection system must be employed to avoid tluctuatlcns due to light from other sources.

2) Source:

Fully digitalized current controlled plasma spark &arc source with minimum32 MHz micro controller. For method optimization, user adjustable excitation and discharge parameters must be provided. Time resolved Spectroscopy must be provided for Improved detection limit &accuracy of detection. Stable plasma Spark and Arc excitation with high energy pressmark, Bad sample detection etc. The source parameters must be able to provide improved detection limits at moderate, high and trace element levels. This should substantially improve repeatability &precision. Required Spark power is approximately, 4-5KW. Spark frequency is between 0-1000Hz. Single Spark Evaluation technique shall be provided instead of integrating the total light over a fixed measurement time.

3) Spark Chamber: Open safety spark stand with quickly operate able sample clamp,

has horizontal &vertical movement for easy sample adjust, Easily replaceable Sample plate for daily cleaning purpose , Electrode hole must be protected from wear & tear while manual/automatic cleaning, Facility for automatic cleaning of electrodes after each spark is preferred, Air Cooling system for electrodes, easily cleanable argon exhaust pipes, High quality fibre optic for light transfer to air optics. Open spark stand design for easy operation and bigger sample size and safety must be provided. Shutter system for UV &Air optics for allowing the light exposure only during sparking.

4) Argon system: Argon flushing system before and during a spark analysis, software

controlled argon conservation/saver,External rare argon purifier for supply of High Purity argon for sparking.

5) Electronics: Electronics for speedy & accurate Spectrometer control , for

conversion of light into electric charge, preamplification, amplification and accurate measurement! integration in to intensity, High speed AD converter, precision Controllers, interface, individual inputs for PM tubes etc. High performance readout system, Single Spark Evaluation technique instead of integrating the total light over a fixed measurement time.

6) Other Accessories: 10KVA Voltage stabilizer (Single phase power supply), dust free

laboratory equipped with computer to support software and printer.

ELTRA CS-500 DETERMINATER

Eltra CS-500 Determinater

Spectrometer is used for analysis of elements like Ni,P,Mn,Si etc in the give ferrous material but for determining carbon and sulphur spectrometer doesn’t show result. For determining % of carbon and suplhur Eltra and Leco apparatus are used. Eltra C S dertermionater is fairly new apparatus as compared with to Leco apparatus and give immediate result within 30 to 50 sec.

The measuring procedure is based on the combustion of given sample using infrared absorption and measurement of the combustion gases . During combustion the suplhur and carbon components in the sample are oxidized in the presence of O2 to form CO2 and SO2. Combuation is obtained by supplying O2 which again acts as a carrier gas. An electronic flow regulator keeps the flow quantity at a constant level of 180 l/hr. Dust trap and moisture absorber ensure that a dry, dust-free gas mixture is supplied to the infrared cell. The signal emitted from the infra-

red cells are selective and corresponds to the CO2 and SO2 concentration of the gas mixture. They are electrically linearized and integrated by the sample weight and digitally displayed as the percentage of Carbon and Sulphur.

The analysis data for every finished analysis is sent to the PC and remains there for result calculation, recalibration and which can be printed.

LECO APPARATUS

Leco Apparatus

Leco apparatus model no 572-100 USA make is used in the Leco lab for determining C and S percentage in ferrous material. In Leco apparatus 0.25gm + 1 mg drilling/ chips of the sample in case of Cast Iron and 1gm + 2mg drilling/chips of the sample in case of steel is weighed accurately on the watch glass with the help of analytical balance. Analysed sample is then transferred to the ceramic cup raised to the combustion tube with the help of raising/locking mechanism and whole assembly is locked to the leak proof Si ring seal.

The combustion takes place in induction furnace inside a completely closed chamber through which O2 is passed at a controlled rate od 1 to 1.5 l/mm. Thus the sample is heated to a high temperature where it is oxidized in presence of O2.

MELTING SHOP

Melting shop basically produces medium carbon iron FG Iron, SG Iron and steel.

Melting Shop at GIF has

1.Two Pillar furnaces Pillar furnace G (200kg capacity) Pillar Furnace H (250 kg capacity)

2. Eight induction furnaces Three set of 3 Ton Capacity Three sets of 3.5 ton Capacity Two sets of 5 ton Capacity

Pillar Furnace

Pillar Furnace

Pillar’s Steel Shell Furnaces are designed to handle the toughest of foundry environments.  With its rolled steel shell, heavy-duty shunts and thick walled copper melting coil, the Pillar Steel Shell Furnace is designed to withstand many years of punishment. The charge to pillar furnace is steel strips and rejected castings. The furnace is internally lined with quartz. When required quality of molten metal is prepared

then it is poured into ladles and taken over to mould boxes with the help of overhead cranes.

INDUCTION FURNACE

Induction Furnace

In induction furnace the strokes are passed through induction coil in the furnaces. The furnaces are becoming very popular because induction greatly decrease sale, can often be operated by one person , requires less maintenance than oil or gas fired furnace and it’s faster. Delivery to the forging machine operator can be effected by slides or automatic handling equipment.

LADLES

Ladles are the equipments used in melting shop to transfer molten metal from furnace to the casting. These are made up of refractory material lined with silica to withstand high temperature. Following types of ladles are used in melting shop:-

a) Drum Ladlesb) S.G. Ladlesc) Hand ladles

Pig Iron

Raw material used in melting shop is pig iron melted from different metals in furnaces. It is used for obtaining other iron compositions by adding required constituents in pig iron.

Composition of pig iron is as follow: Carbon 3.6 to 4.2%

Silicon 1.75 to 2.25 %Manganese 0.5 to 1.0 %Sulphur 0.6 % maxPhosphorous 0.1 to 2.2 %

S.G. Iron

S.G. iron is not a single material but is part of a group of materials which can be produced to have a wide range of properties through control of the microstructure. The common defining characteristic of this group of materials is the morphological structure of the graphite. In S.G. irons the graphite is in the form of spherical nodules rather than flakes (as in grey iron), thus inhibiting the creation of cracks and providing the enhanced ductility that gives the alloy its name. The formation of nodules is achieved by addition of nodulizing elements, most commonly magnesium and less often, cerium, into the melt.

S.G. Iron structure

Composition for S.G. Iron

Carbon 3.3 to 3.4 %Silicon 2.2 to 2.8 %Manganese 0.1 to 0.5 %Magnesium 0.03 to 0.05%Phosphorous 0.005 to 0.02 %Sulphur 0.005 to 0.002%

F.G. Iron or Gray Iron

Grey iron is a cast iron alloy that has a graphitic microstructure. Its named after the gray color of the fracture it forms, which is due to the

presence of graphite. It is the most common cast iron and the most widely used cast material based on weight. Gray iron is a common engineering alloy because of its relatively low cost and good machinability, which results from the graphite lubricating the cut and breaking up the chips. It also has good galling and wear resistance because the graphite flakes self lubricate. The graphite also gives gray iron an excellent damping capacity because it absorbs the energy. It also experiences less solidification shrinkage than other cast irons that do not form a graphite microstructure. The silicon promotes good corrosion resistance and increase fluidity when casting. Gray iron is generally considered easy to weld.

Composition for F.G. Iron/ Grey Iron

IronCarbon 3.5 to 3.6 %Silicon 2.6 to 2.7 %Manganese 0.5 to 0.6 %Suplhur 0.1 % maximumPhosphor 0.2% maximum

Steel 5339

Steel 5339 is also a product used in certain steel castings

Composition for steel 5339 is as follow:

Carbon 0.3 to 0.4 %Silicon 0.5 to 0.6 %Manganese 0.3 to 0.6 %Sulphur 0.025% maxPhosphorous 0.05 to 0.07 %

COMPRESSOR SHOP

INTRODUCTION Compressors in industries are required for pneumatic tools and controls, which require compressed air at desired pressure and sufficient volume.

BALANCE OPPOSED COMPRESSOR

Modern compressors employ:

a) Inner CoolerCooling by water into passages provided in the cast casing expressly for the

purpose(inner-cooling). This method greatly improves lubrication of the reciprocating compressors. So far this method has failed to secure considerable saving in power as it does not bring the compression process any nearer to isothermal. The cause is the difficulties with heat exchanges between the gas flow and cooling water.

b) Inter CoolerCooling the gas in intercoolers mounted between separate

stages(intercooling). In centrifugal compressors, intercoolers are usually installed between stage groups, which makes the design of the plant more simple. Unique compressor designs have been reported with each centrifugal stage followed by an intercooler. Such compressors are called isothermal. They are economical in operation, yet complicated in design and expensive.

c) Combined(inter and inner cooling)This is the most efficient and extensively used method, even though it complicates the design and increases the cost of the plant.

d) Cooling by introducing jets of water into the gas flow ahead of the first stage of the compressor. With this method gas loses part of its heat.

TYPES OF COMPRESSORS:

The type of compressor used depends on the operational demands with regard to working pressure and delivery volume.

Compressors fall into two categories:-

1)The displacement principle where air is compressed by containing it in a chamber and the volume of this chamber. This type is called piston compressor e.g. Reciprocating piston compressor, rotary piston compressor

2)The second group operates on the air-flow principle, by drawing in air on one side and compressing it by mass acceleration.

PISTON COMPRESSORS:

Reciprocating piston compressors: The reciprocating piston compressor is, at the present time, the most widely used compressors. It can be used not only for compressing to low and medium pressures, but also to high pressure. The pressure range extends from 1x105 Pa to several thousand bar.

Multistage compressors are required for compressing to higher pressure. The drawn in air is compressed by the first piston, cooled, and then compressed further by the next piston. The volume of the second compression chamber is smaller in terms of compression ratio. Heat arises during compression must be removed by the cooling system.

Reciprocating piston compressors are made as air-cooled designs and also water-cooled designs. The optimum ranges for reciprocating piston compressors are

upto 4x105 Pa Single Stageupto 15x105 Pa Double Stageover 15x105 Pa Triple Stage or Multi-Stage

DIAPHRAGM COMPRESSOR:This type of compressor belongs to the piston compressor group. The piston is separated from the suction chamber by a diaphragm. i.e. the air doesn't come into contact with the reciprocating parts. Thus, the air is kept free of oil.

For this reason it is preferred in the foodstuffs industry, the pharmaceutical and chemical industries.

ROTARY PISTON COMPRESSOR:

The rotary piston compressor is a compressor with rotating pistons. At the same time, chambers are compacted and the air in these chambers is compressed.

SLIDONG VALVE ROTARY COMPRESSOR:

An eccentrically mounted rotor rotates in the cylinder housing having inlet and outlet slots. The advantage of this compressor are its compact dimensions and also its quiet running and smooth, steady air delivery. Sliding vanes are contained in slots in the rotor and form chambers with the cylindrical wall. When rotating, the centrifugal energy forces the vanes against the wall, and owing to the shape of the housing the chambers are increased or reduced in size.

TWO-AXLE SCREW COMPRESSOR

Two intermeshing rotates, one having a convex profile and the other having a concave profile, displace the axial entering air to the other side.

ROOTS BLOWER:

In these compressors, the air is conveyed from one side tot he other without any change in volume. The piston edges produce sealing on the pressure side.

FLOW COMPRESSOR( TURBO COMPRESSORS):

These work on the air-flow principle and are especially suitable for large delivery volumes. Flow compressors are made as axial type and radial type.The air state is converted in one or more turbine wheels to flow velocity .This kinetic energy converted to pressure energy.Acceleration from the chamber to chamber radially outwards, reversal of the flowing air and return to the shaft, from there, again acceleration outwards.

Factors to be Considers for Compressor Proper Working:

Prior to taking up installation work of the air compressor, it is necessary to thoroughly check the unit for any transit damages and after satisfying the installation work should be taken up.

The compressor unit should be installed on a level ground where the floor is of uneven level, it is advisable to mount the compressor on two wooden blocks, which can be bolted to the compressor footing. Check and correct level by placing a spirit on top of the tank, and also over the compressor footing. Foundation bolts are not normally, but where the ground is very uneven, and as a result of which, the compressor unit vibrates, it is advisable to grout the foundation bolts on the ground, and then install the compressor. The mounting bolts used in the packing case of the compressor unit, could be made use for this purpose.

It is important that adequate ventilation exists in the area where the compressor is installed, and it would be preferable to install the compressor near a window or wherever cool air could be drawn while the compressor near a furnace or any place where the atmosphere air is very hot.

When the compressor is placed near a wall there should be minimum distance of 400mm between the compressor and the wall or any other enclosure. This is necessary for adequate cooling of the compressor unit, and also for easy access.

LUBRICATION:

It should be noted that oil has been drained from all compressors prior to dispatch of the units from the factory. Oil should be filled by unscrewing the bather filter by hand, and oil of proper grade. "Maintenance", should be filled till the level reaches the top line in the visible oil level indicator. It is important that the oil level should not be allowed to go below the bottom line nor above the top line.

WIRING

Power lines should be connected in accordance with the wiring diagram pasted with

the starter cover. After connecting power line start the unit momentarily and observe the direction of rotation of the compressor. The direction should be anti-clockwise when seen from the front and an arrow indicating this direction is marked on the compressor block on the front side. If the direction is not correct, change the direction by interchanging any of the two phases in the main switch.

TAIL RUN

The ball and roller bearings in the electric motors are packed and filled with bearing grease, and these bearings should be repacked once every year.

ACCESSORIES IN COMPRESSOR

OIL SEPERATORThe oil supplied to the compressor cylinder gets mixed with the moisture from the inlet air gets mixed with the moisture from the inlet air. This oil and water mixture is carried into the intercooler where the moisture gets condensed .Then the air goes to the high pressure cylinder. Finally the air with the condensate mixture gets to the after cooler where most of the condensate gets eliminated. However, the use of an oil separator is still recommended to completely segregate the oil and water mixture.

AFTER COOLERWhen the compressed air delivered by the compressor is to be used for an application where high temperatures are not desirable or the hot air passing through the piping is harmful to it, then the use of an after cooler is recommended.

SAFETY VALVESafety valves are installed on the intercooler, after cooler and receiver. When the pressure inside the safety valve exceeds the present value, the valve opens against the spring force, releasing the compressed air to the atmosphere. The valve is closed by the spring force when the pressure drops below the set value.

AIR FILTERAir filter should be fitted to the air intake pipe, without fail. The air to be compressed must be very clean and free from foreign particles. Dust or dirt can cause serious damage to the compressor and can adversely affect its life. Many types of filters are in use. The kirloskar-Hitachi air filter is designed for the best performance. It has wire screens oil bath and steel wool arrangement, wherein the suction air filtered through screens is directed along the oil surfaces and then through the steel wool. Hence, it gets thoroughly filtered before it actually enters the filter.

MUFFLER (Suction Silencer) In case the noise of the compressor causes disturbance to the neighborhood, particularly when hospitals , schools or private residences are nearby, a suction silencer can be installed to control the noise.

FUSIBLE PLUGIn order to safeguard the plant against damages due to excessive temperature developed from compressed air, a fusible plug should be used. The alloy of the plug melts if the temperature of the compressed air exceeds the pre-designed value and releases the hot compressed air to the atmosphere giving a hissing noise. It should be installed in the delivery pipe just after the compressor to take care of the valves,

valve plates etc.

RECIEVER A receiver is used in the compressor system to achieve the following-to obtain a vibration free and smooth flow, to dampen the pulsation which occurs due to separate moisture and oil as condensates to reduce the temperature and to store the compressed air. The receiver also prevents the pulsation pressure waves from reaching resonance level and bursting the pipes and their joints.

LOW OIL PRESSURE SAFETY SWITCHIf the oil pressure falls below the present value, the pressure switch, being electrically connected to the compressor controller, brake the contact and stops the prime mover and thus stops the compressor and safeguard the bearings. This ensures positive flow of oil and prevents any overheating due to the low oil pressure. An alarm can be connected electrically to buzz as soon as oil pressure fall below the present value.

LOW WATER PRESSURE SAFETY SWITCHIf the water pressure falls below the present value, the pressure switch being electrically connected to the compressor controller, brakes the contact and stops the motor. This ensures positive flow of water and prevents any over heating due to low water pressure. An alarm can also be connected electrically to buzz as soon as water pressure falls below the pre-set value.

HIGH DELIVERY TEMPERATURE ALARM & SAFETY SWITCHIf the delivery temperature rises above the present value, the safety switch being electrically connected to the compressor controller, brakes the contact and stops the motor. It is installed on the delivery pipe after the compressor. An alarm is also connected to buzz as soon as the air delivery temperature crosses the present value.

HIGH LUBRICATION OIL TEMPERATURE ALARM & SAFTY SWITCH If the oil temperature rises above the present value, the temperature switch, being electrically connected to the controller, brakes the contact and stops the motor. It is installed on the crank case. An alarm is also connected to buzz as soon as the temperature exceeds the present value.