Dlw Charbag Project

8/11/2019 Dlw Charbag Project

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INDIAN RAILWAY HISTORY

Indian railway is the state-owned railway company of India. It

comes under the ministry of railway has one of the largest and

busiest rail network in the world transporting over 18 million

passengers and more than 2 million tonnes of freight daily. Its

revenue is rupees 107.66 billion its is the worlds largest

commercial employ, with more than 1.4 million employees. It

operates rail transport on 6,909 stations over a total routes length

more than 63,327 kms (39350miles).The fleet of Indian railway

including over 200,000 (fright) wagons, 50,000coaches and 8000

locomotive. It also owns locomotive and coach production

facilities. It found in 1853 under the EAST INDIAN COMPANY.


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COMPRESSOR

The compressor is a two stage compressor with one low of

pressure cylinder and one high pressure cylinder. During the first

stage of compression it is dine in the low pressure cylinder where

suction is through a wire mesh filter. After compression in the L.P

cylinder air is delivered into the discharged manifold at a pressure

of 30/35 psi. working of the inlet and exhaust valves are similar to

that of exhauster which automatically opens or close under

differential air pressure.

For intercooling air is then passed through a radiator know as

intercooler. This an to air cooler where compressor air passed

through the element tubes and cool atmospheric air is blown on

the outside fins by a fan fitted on the expressor crankshaft. Cooling

of air this stage increases the volumetric efficiency of air before it

enters the high pressure cylinder .A safety valves known as

intercooler safety valves set at 60 psi is proved after the

intercooler as a protection against high pressure developing in the

after cooler due to defect of valves.


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After the first stages of compression and after cooling the air is

again compressed in a cylinder of similar diameter to the pressure

to 135-140 psi in the same way. This is the second stage of

compression in the high pressure cylinder. Air again needs cooling

before it is finally sent to the air reservoir and thus done while the

air passes through a set of coiled tubes after cooler

WORIKING OF COMPRESSOR

An air compressor is a device that converts powers (usually froman electric motor, a diesel engine or a gasoline engine) into kinetic

energy by compressing pressurizing air, which, on command, can

be released in quick bursts. There are numerous method of air

compression, divided into either positive-displacement or

negative displacement types.

Positive-displacement air compressor work by forcing air into achamber whose volume is reduce to compress the air. Pistontype

air compressors use this principal by pumping air into an air

chamber through the use of the constant motion of pistons. They

use unidirectional valves to guide air into chamber, where the air

is compressed. Rotary screw compressors also use positive-

displacement compression by matching two helical screws turn.

Vane compressor use a slotted rotor with varied blade placement

to guide air into a chamber and compress the volume.


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Like a small internal combustion engine, a conventional piston

compressor has crankshaft, a connection rod and piston, a cylinder

and a valves head. The crankshaft is driven by either an electricmotor or a gas engine. While there are small models that are

combined of just the pump and motor, most compressors have an

air tank to hold a quantity of air within a present pressure range.

The compressed air in the tank drive the air tools, and the air

tools, and the motor cycles on and off to automatically maintain

pressure in tank.

At the top of the cylinder, youll find a valve head that holds the

inlet and discharge valves. Both are simply thin metal flap-one

mounted underneath and one mounted on top of the valve plate.

As the piston moves down, a vacuum is created above it. This

allows outside air at atmospheric pressure to push open the inlet

valve and fill the area above the piston. As the piston moves up, the

air above it compresses, hold the inlet valve shut and push the

discharge valve open. The air moves from the discharge port to the

tank. With each stoke, more air enter the tank and the pressure

rises.

Compressors user a pressure switch to stop the motor when tank

pressure reaches a preset limit-about 125 psi for many single-stage models. Most of the time, through, you dont need that much

pressure. Therefore, the air line will include a regulator that you

set to match the pressure requirement of the tool youre using. A

gauge before the regulator monitor pressure and a gauge after the

regulator monitor air-line pressure. In addition, the tank has a

safety valve that opens if the pressure switch malfunctions. The

pressure switch may also incorporate an unloader valve that

reduces tank pressure when the compressor is turned off.


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Many articulated-piston compressors are oil lubricanted. That is,

they have an oil bath that splash-lubricant the bearing and

cylinder walls as the crank rotates. The piston have rings that helpkeep the compressed air on top of the piston and keep the

lubricating oil away from the air in aerosol farm.

LODING UNLODING OF AIR

COMPRESSER.

In an air compressor, there are device that automatically stop the

compressor from compressing air. A mechanical unloader is

sometimes installed in large air compressors such that air valves

are open when the set pressure is attained. When this happen, the

drive motor continues running but no air presser is pumped to the

receiving tank during the unloading period. When the pressure intank is reduced to a set level, the air valves in the compressor

automatically closes and air pressure is again developed, this

called pressure loading. In many instances, compressors are

controlled only by pressure switches to automatically stop the

drive motor at a set pressure and restart at a lower pressure.


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COMPRESSOR PERFORMANCE:

Capacity of a compressor is the full rated volume of flow of gas

compressor and delivered at condition of total temperature, total

pressure, and composition prevailing at the compressor inlet. It

sometimes means actual flow rate ,rather than rated volume of

flow. This is also termed as FAD (Free Air Delivery) i.e air at

atmospheric conditions at any specific location. Because the

altitude, barometer ,and temperature may vary at differentlocalities and at different times, it follows that this term does not

mean air under identical or standard conditions. Compressor

efficiency are volumetric efficiency, adiabetic efficiency,

isothermal efficiency an mechanical efficiency.

ISOTHERMAL EFFICIENCY

Thermal power does not include power needed to overcome

friction and gives efficiency which is lower than adiabetic

efficiency.


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VOLUMETRIC EFFICIENCY

Volumetric efficiency=FAD/Compressor displacement

Where- Compressor displacement=

D is the cylinder bore

L is the stroke length

S is the compressor speed

N is the number of cylinders

n =1 for single acting

n=2 for double acting


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COMPRESSED AIR SYSTEM COMPONENTS

Compressed air systems consist of following major components:

Intake air filters, inter stage coolers, after coolers, air dryers, andmoisture drain traps, receivers, piping network, filters, regulators

and lubricators. Intake Air Filters: Prevent dust from entering

compressor; Dust causes sticking valves, scoured cylinders,

excessive wear etc.

Inter-stage Coolers:

Reduce the temperature of the air before it enters the next

stage to reduce the work of compression and increase efficiency.

They are normally water-cooled.

After Coolers :

The objective is to remove the moisture in the air by

reducing the temperature in a water-cooled heat exchanger.

Air-dryers :The remaining traces of moisture after after-cooler are

removed using air dryers, as air for instrument and pneumatic

equipment has to be relatively free of any moisture. The moisture

is removed by using adsorbents like silica getl/activated carbon,

or refrigerant dryers, or heat of compression dryers.

Moisture Drain Traps :

Moisture drain traps are used for removal of moisture in the

compressed air. These traps resemble steam traps. Various types

of traps used are manual drain cocks, timer based / automatic

drain valves etc.


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Receivers :

Air receiver are provided as storage and smootheningpulsating air output-reducing pressure variations from the

compressor.

Efficient Operation of Compressed Air Systems

Location of Compressors The location of air compressors

and the quality of air drawn by the compressors will have a

significant influence on the amount of energy consumed.

Compressor performance as a breathing machine improves with

cool, clean, dry air at intake.

Cool air intake As a thumb rule, "Every 40C rise in inlet air

temperature results in a higher energy consumption by 1% to

achieve equivalent output". Hence, cool air intake leads to a more

efficient compression.

It is preferable to draw cool ambient air from outside, as the

temperature of air inside the compressor room will be a few

degrees higher than the ambient temperature. While extending air

intake to the outside of building, care should duct with minimum

number of bends.

Dust Free Air Intake :

Dust in the suction air causes excessive wear of moving parts

and results in malfunctioning of the valves due to abrasion.

Suitable air filters should be provided at the suction side. Air

filters should have high dust separation capacity, low-pressure

drops and robust design to avoid frequent cleaning and

replacement.


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Air filters should be selected based on the compressor type

and installed as close to the compressor as possible. As a thumb

rule "For every 250 mm WC pressure drop increase across at the

suction path due to choked filters etc., the compressor power

consumption increases by about 2 percent for the same output"

Hence, it is advisable to clean inlet air filters at regular intervals to

minimize pressure drops. Manometers or differential pressure

gauges across filters may be provided for monitoring pressure

drops so as to plan filter-cleaning schedules.

Dry Air Intake :

Atmospheric air always contains some amount of watervapour, depending on the relative humidity, being high in wet

weather. The moisture level will also be high if air is drawn from a

damp area for example locating compressor close to cooling

tower, or dryer exhaust is to be avoided The moisture-carrying

capacity of air increases with a rise in temperature and decreases

with increase in pressure.

Efficacy of Inter and After Coolers :

Efficacy is an indicator of heat exchange performance- how well

intercoolers and after coolers are performing. Inter-coolers are

provided between successive stages of a multi-stage compressor to

reduce the work of compression (power requirements) by

reducing the specific volume through cooling the air apart from

moisture separation. Ideally, the temperature of the inlet air at

each stage of a multi stage of a multi-stage machine should be the

same as it was at the first stage. This is referred to as "perfect

cooling" or isothermal compression. The cooling may be imperfect

due to reasons described in earlier sections. Hence in actual

practice, the inlet air temperatures at subsequent stages than the

normal levels resulting in higher power consumption, as a larger

volume is handled for the same duty.


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Pressure Setting :

Compressor operates between pressure ranges called as loading

(cut-in) and unloading (cut-out) pressures. For example, a

compressor operating between pressure setting of 6 - 7 kg/cm2

means that the compressor unloads at 7 kg/c m2 and loads at 6

kg/cm2. Loading and unloading is done using a pressure switch.

For the same capacity, a compressor consumes more power at

higher pressures. They should not be operated above their

optimum operating pressures as this not only wastes energy, but

also leads to excessive wear, leading to further energy wastage.

The volumetric efficiency of a compressor is also less at higherdelivery pressures.

Reducing Delivery Pressure :

The possibility of lowering (optimizing) the delivery

pressure settings should be explored by careful study of pressure

requirements of various equipment, and the pressure drop in the

line between the compressed air generation and utilization points.


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AIR BRAKE

Introduction :An air brake is a conveyance braking system actuated by a

compressed air. Modern trains rely upon a fail preventive air

brake system that is based upon the design patented by George

Westinghouse on March 5, 1872. In the air brakes simplest form,

called the straight air system, compressed air pushes on a piston

in a cylinder. The piston is connected through mechanical linkage

to brake shoes that can rub on the train wheels using the resulting

friction to slow the train.

Air brake system operation :

The compressor in the locomotive produces the air supplied

to the system. It is stored in the main reservoir. Regulated

pressure of 6 kg/cm^2 flows to the feed pipe through the feed

valve and 5-kg/cm^2 pressure by a drivers brake valve to the

brake pipe. The feed pipe through check valve charges airreservoir via isolating cock and also by brake pipe through

distributor valve. The brake pipe pressure controls the distributor

valves of all the coaches/wagons which in turn control the flow of

compressed air from air reservoir to brake cylinder in application

and from brake cylinder to atmosphere in release.

During application the driver in the loco lowers the B.P pressure.

This break pipe pressure reduction causes opening of brakecylinder inlet passage and simultaneously closing of brake

cylinder outlet passage of the distributor valve. In this situation,

auxiliary reservoir supplies air to brake cylinder. At application

time, pressure in the brake cylinder and other brake

characteristics are controlled by distributor valve.


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During release the B.P pressure is raised to 5 kg/cm^2. This

break pipe pressure causes closing of break cylinder inlet passage

and simultaneously opening of break cylinder outlet passage of

the distributor valve.


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DESCRIPTION OF PARTS OF

EXPRESSOR/COMPRESSOR

Cylinders :

Compressor has two 196,875 mm diameters low pressure

cylinders and one 139.7 mm diameter high pressure cylinder.

Cylinders are made grey iron casting with hexagonal fins for better

cooling.

Cylinders Heads and Valves :

This compressor is equipped with three cylinder heads; the valves

are individual disc type, loaded with springs, operated due to the

differential pressure between the upstream and downstream

pressure. Inlet valves contain an integrated unloader that is

actuated by the unloader valve via a heavy spring which unload

the compressor whenever a set main reservoir pressure is reached

and not to exceed 140 psig (9.8 kg/cm^2).


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Crankshaft and Connecting Rods :

Crankshaft is made of special alloy forged steel, so that

deflection is minimized and the wear is reduced. A fan is mounted

on the one end.

The drive to the crankshaft is taken from the engine through

a coupling. Rotational motion of the crankshaft is converted to

reciprocating motion by slider crank mechanism.

Low pressure and high pressure stage connecting rods are

interchangeable and are made of forged steel fitted with bimetal

bearing on crankpin end needle roller bearing on wrist pin end.

However the lower portion and upper portion of the connecting

rod must be kept as a matched set with orientation marks on the

same side. The connecting rods are mounted over the crankpin

adjacent to one another.

Compressor Pistons :

The low pressure pistons are made of aluminum and

elliptically ground on the outside diameter. The high pressure

piston is cast iron.

Both low pressure and high pressure piston have two cross

beveled oil controlled rings, one nose scraper ring and one taper

faced compression ring on the top. Piston reciprocates taking the

power from the connecting rod.


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Main Bearings :

Two double row balls bearing are assembled on either side

of the crankshaft which takes the misalignment in geometrical

tolerance and operations. The main bearings of the compressor

and lubricated by the oil taken up during compressor operation

and passes through the pocket in the end cover.

End Cover :

End cover is made of cast iron, which has more stiffness and

deflection is minimized, which increases the rigidity.

Lubrication of Compressor :

The compressor lubricating system is piloted by the gear

drive oil pump. The oil pump circulates the rid under pressure.

Drive is taken from the crankshaft by means of a set of gears with

an ideer, to pump the oil through the system. A primary oil filter

which faces the inner side of the crankcase bottom, filter the oil to

prevent the ingress of external agents like dust and other solidparticles from entering into the pump and the lubricating system.

The filtered oil is passed through the groove to the disturbing ring.


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Through the distributing ring, the lubricating oil flows to each

crank pin in the crankshaft through the oil holes drilled in it. The

oil lubricates the inner bearings of the connecting rods through

the groove provided and the needle roller bearing and gudgeon

pin at small end through for holes drilled in the connecting rods. A

relief valve fitted on the body of the oil pump maintains the oil

pressure between 2.2 to 3.5 kgf/cm^2. It can be adjusted to the

desired oil measure.

Intercooler :

The intercooler reduces the temperature of the compressed

air leaving the first stage prior to entering the second stage inorder to improve the overall thermodynamics efficiency of the

system The air from atmosphere is forced to flow configuration to

reduce the temperature of the compressed air.

After Cooler :

The after cooler assembly reduces the outlet temperature. The

cooler made with external Lined cooper pipes. A safety valve is

provided at the manifold of the after cooler assembly, which has

an opening pressure of 200 psi. Both intercooler and after cooler

has a drain valve at the bottom to drain the condensate.


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OVERHAULING AND

MAINTAINANCE PROCEDURE

Exterior Surfaces-

Before the compressor is disassembled, the exterior surface of the

must be thoroughly cleaned. Parts should be marked to ensure

that each would be reassemble in the proper location. Care should

be taken when handling parts so as not to damage parts. When

cleaning the parts, do not put main bearing, crankshaft, connecting

rods valves, piston, piston ring or wrist pins, plunger, pump

components in the same basket with other compressor parts.

Cylinder heads, cylinder, crankcase, end cover, casting manifolds,

should be placed in a cleaning solution and left other long enough

to ensure proper cleaning. After removal from the cleaning

solution these parts should be wire brushed and inspected for

defects.

The piston, crankshaft and connecting rods should be thoroughly

cleaned and magnetic particle inspected for defects.

Use the low pressure jet for clean, dry air to blow the surface clean.


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CLEANING, INSPECTION AND

REPARING

CLEANING-

Clean all other serviceable metal parts to facilitate inspection.

After the parts have been cleaned, they MUST BE completely dried.

Use a low pressure jet of clean dry air to blow the parts dry

Make certain that all drilled oil passages in connecting rods,

crankshaft etc; are clean and free from obstruction and that the oil

pressure indicator tube is not bend or damaged.

IMPORTANT: All gaskets, rubber parts, copper washer, self-locking

hardware and split pins ARE TO BE SCARAPPED. ONLY NEWmanufactured recommend parts are to be use in place of the

scrapped parts during the assembly procedure to permit the best

fit and performance.

CYLINDER

Replace any cylinder that is found to be damage beyond repair this

may include cylinder with damaged or broken fins as determined

or broken fins as determined by inspection.


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The cylinder should be cleaned after removal, prior to any

inspection or reconditioning. Examine the cylinder for score

marks or ridges at the ring travel in surface.

Aluminum and cast iron pistons-

At the time of compressor overhauling the piston should be

removed, cleaned and inspected for excess wear. The wrist pin

should be removed from the piston and connecting rod assembly

with the tool.

Piston ring grooves must be square and free from wear edges.

Measure the piston and cylinder diameter and it must be with in

limit.

Where applicable, minor scruff marks or scratches can be

smoothed with a file.

Wash piston thoroughly to remove any foreign particles, and then

blow it dry with clean dry air.

Cover both end of wrist pin bore and piston groove to keep foreign

material out of the bore until the wrist pin is installed.

PISTON RINGs


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Compressions rings are marked on top ensure proper application.

Oil control ring are not marked as they may be applied either side

u.

To properly apply the piston rings, use the correct ring expanding

installing tool according to the piston diameter. Piston assembly

should be fitted through the bottom of the cylinder rather than

through the top because the bottom of the cylinder is chamfered

to prevent damage to the ring on enter. Therefore, ring must have

at least minimum clearance at the lower end of the cylinder. Piston

ring should never be filed to obtain clearance.

Taper face type compression ring are to be assemble in the piston

with facing upward position. The nose scraper ring is to be

assembled with notch down towards the bottom of the piston.

CRANKCASE

Replace the crankcase, if it damage beyond repair otherwise clean

the crankcase.


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END COVER

Replace the end covers if is craned, broke, or otherwise damaged

beyond damaged beyond repair.

CRANKSHAFT

If the crankshaft is removed for any reason , it should be given a

thorough cleaning with solvent , particularly during overhauling

work , since metallic particles among lodge in the oil passage . All

oil drilling must be cleaned thoroughly.

During scrubbing, solvent should be directed into the passage

under approximately 172 kpa, washing and brushing must be

repeated until the oil passage and crankshaft is absolutely cleaned.

The crankshaft should be replaced if any of the following defect is

noticed:

1.Bent or cranked.

2. Crank pin is at or beyond the condemning limit.


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CONNECTING ROD

Connecting rods used in the compressor are equipped areequipped with bearing insert the bearing insert should be

replaced at the time of overhauling or any time their condition

warrants replacement.

All oil passage must be cleaned thoroughly. A long handled bristle

brush having slightly over 8mm diameter is recommended for

cleaning passages. During scrubbing, solvent should be directedinto the passage under approximately 25 psig pressure.

Wrist pin bore must be parallel with crank pin bore in both planes

to be within 0.0008mm.

Crank pin bore must be square with both the planes within

0.0004mm.


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PERFORMANCE TESTING AFTER

RECONDITIONING

INTRODUCTION

The compressor which has gone through a inspection and

recondition should be put to a wearing run for a considerable

period.

It should be remembered that the wear is run must be done at a

reasonable speed whenever it has under gone recondition and

general overhauling particularly piston ring and cylinders allow

sufficient time for the self-adjustment of the new part that a

replaced. There will be non-uniform and rapid increase in

temperature after sometime it will regain normal temperature.Since the part have been replaced , there is a change for

temperature to vary never allow the compressor to run at high

speed because if there is any misalignment , it may sever damage

to the unit.

TEST PROCEDURE

Every before operation should be followed up with much care so

that the benefit achieved from precise remachining and

refinishing should not be lost in wear period .


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Construct test stand at the place where major overhauling is

carried out ,if new test stand is not provided , we can conduct the

wear is test the locomotive itself. Use a variable speed motor of

about 100hp or a constant speed motor with a multiple speed gear

box to drive the compressor use belt drive provided. No thrust is

allowed on main bearings of compressor. Maintain the speed

range for testing between 400-1100 rpm and the install speed

should not be less than 400rpm to provide sufficient lubrication to

all the part during the wear in.

Provide lubricating oil and auxiliary cooling fan. Stop the

compressor for cooling and make to run at the minimum speed

and pressure ,if there is high temperature and if its persist ,examine check whether the cooling air is sufficient , proper

lubrication and correct alignment and clearance.

OIL SEAL ASSEMBLY-

The oil seal must be assembly in the crankcase and in cover with

two lips facing inwards . Install the oil seal without lubrication on

the seal lips.

When installing an oil seal, care must be exercise to ensure that

the seal is not damaged by the keyway or should of the crankshaft.

CYLINDER HEAD ASSEMBLY

Install the inlet and outlet valve using the new copper washers.

Install the valve plugs with anti-seize lubricants on the threads .

Proper check the leakage of any part.


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After this assemble the intercooler and after cooler.


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