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DIESEL LOCO – COMPRESSOR

January 5, 2021, 7:30 PM

COMPRESSOR

In IRAB1 (straight air brake) fitted loco have only compressor. It is provided in the compressor room. The main function of compressor is to provide compress air for various purposes.

It has one crankshaft and two bearings. One end of crank shaft is connected to engine main crankshaft with fast coupling and other end to extension shaft no.2 with flexible coupling. It has 03 cylinders, 02 low pressure cylinders in ‘V’ shape and 01 high pressure cylinder in vertical position. Breather valve is provided in the sump to avoid pressurization of sump. 20 liter lube oil filled in compressor sump for lubrication. For circulation of lube oil one chain and sprocket driven pump is provided in sump. Filling cap is provided for lube oil filling and spy glass/dipstick gauge for checking of oil level.

Compressor and MR Charging :- Compressor charges the main reservoir with pressurized air. Each cylinder have inlet and discharge valve working on principle of differential pressure.

It’s working to charge main reservoir with pressurized air, has 03 cylinders, two big cylinders are called low pressure cylinders and small is called high pressure cylinder. Low pressure cylinders having 02 inlets and 02 discharge valves, inlet valve is connected to air intake filter and

discharge valve to intercooler. High pressure cylinder having 01 inlet and 01 discharge valves, inlet valve is connected to inter cooler and discharge valve to cooling coil through after cooler. Inlet valves have un-loader assembly, its connection given to EPG.

When piston travel from TDC to BDC in low pressure cylinder inlet valve opened and filtered atmospheric air entered in cylinder. When piston travel from BDC to TDC inlet valves close and pressure is increased in cylinder hence discharge valve gets open and air goes in inter cooler where it cools by air. Safety valve (setting 4.2 kg/cm2) is provided on inter cooler to safeguard it.

When piston travel from TDC to BDC in high pressure cylinder inlet valve open hence air from inter cooler entered in cylinder. When piston travel from BDC to TDC inlet valves close and pressure is increased in cylinder hence discharge valve gets open and air goes in cooling coil through after cooler where it gets cool by air and charged MR1. Safety valve (setting 10.5 kg/cm2 ) is provided on outlet pipe of MR1, it discharge over pressure and safe guard the MR tank. From MR1 air goes to MR2 through air dryer and NRV. MR1is provided in under truck between fuel tank and rear truck and MR2 between fuel tank and front truck.

MR1 pressure is used on different places as below :

Control air pressure reservoir – It is charged with 5 kg/cm2 . NS1 reducing valve and COC is provided in nose compartment to convert MR pressure into 5 kg/cm2 . This pressure is used to operate electro pneumatic contactor. It has drain cock and pressure gauge mounted on nose compartment wall in loco pilot cab.

Sanders – Sanding between wheel and rail, sanders valve are provided.

Wipers – Both side looking glass having wipers which are operated by its servo motor.

Horns – Horn switches are provided on both control stand and its coc in nose compartment.

MR1 equalizing pipe – In multiple unit MR pressure is equalizing when MR equalizing pipe is connected between the loco which is charged by duplex valve.

Feed pipe – In twin pipe brake system feed pipe is charged with 6kg/cm2 through D24B valve, its 11 /4” coc.

EPG – Its main function is to maintain MR pressure between 8 to 10 kg/cm². Its EP valve and cut out cock is provided in compressor room on the radiator room wall. Pressure switch, pressure gauge and COC is provided in nose compartment, its toggle switch is provided on nose compartment.

When MR pressure reach to 10 kg/cm², EPG operates and send air pressure on un-loader assembly as well as auto drain valve. Due to air pressure on un-loader assembly inlet valve remains in opened condition and air will not compressed. This process is called unloading / governor cut out. Auto drain valve drains moisture from MR1.

When MR pressure drops up to 8kg/cm2, EPG comes in its balance/cut in position and its exhaust port opened, which vents the air from un-loader assembly as well as auto drain valve. Due to no air pressure on un-loader assembly, inlet valve closed and restarts the air compression. This process is called loading / governor cut in. Auto drain valve drains moisture from MR1.

In multiple unit EPG helps in loading and unloading of MR in all locos at a time. Normal position of EPG toggle switch is ON and in case of MU in trailing loco it is in OFF position.

MR2 – It is located between fuel tank and front truck. MR2 air is used to operate different valves of brake system. J-filter and its coc provided on MR2 outlet pipe.

Drain cocks are provided on MR1, MR2, J-filter, control reservoir to drain moisture.

Lubrication of compressor – Compressor sump has filled with 20 litters Lube oil, it has a positive displacement type pump provided in the sump which is rotates through chain and sprocket. Compressor shaft rotating pump starts work and distribute pressurized oil on following places.

1. Relief valve
2. Needle valve
3. Distribution ring.

From distribution ring following equipments are lubricate

1. Crank pin
2. Piston pin
3. Cylinder liner

Brass needle valve is provided to check the working of pump when engine in working condition. Due to oil pressure needle valve spindle projected.

Compressor sump is connected breather valve sump.

Checking of Compressor oil- Spy glass and dipstick gauge are provided to check oil level in the sump. While checking oil level through dipstick gauge, Engine to be shut down.

Brass Needle Valve Not Project Out – It is provided to check the working of pump when engine in working condition. If it project out on Engine raise, note in Loco repair book. If it does not project out, loose check nut on needle valve if oil comes from it, it means pump is working but needle valve defective book in repair book. If oil does not comes out check the oil level in sump if oil level is satisfactory, it means pump is defective, fail the loco. If oil level is below minimum mark then inform PCOR.

MR pressure dropping on run – In this situation loco pilot will not leave control stand and keep sharp watch on MR & BP pressure gauge, work the train and follow traffic rules. When MR pressure comes below 6 kg/cm2 apply A9 to stop the train and keep A9 in emergency & SA9 in application position and also secure the train as per requirement. Blow the whistle code to protect/secure the train from rear by Guard as per traffic rule. Further do the trouble shooting.

EXPRESSER

In dual brake loco expresser is provided instead of compressor. The combination of exhauster and compressor is called expresser; it is provided in the expresser room. The main function of expresser is to provide compress air and vacuum for various purposes.

It has 6 cylinders, 3 for compressor and 3 for exhauster. Two crank pin provide on expresser crank shaft, each pin has 3 connecting rods.

Each cylinder head of exhauster has two inlets and exhaust valve, all inlet valves of 3 cylinders are connected with inlet pipe and inlet pipe is connected with VA1B control valve, the inlet pipe is called vacuum reservoir. Similarly exhaust valves are connected with exhaust pipe in under truck.

When exhauster cylinder piston travel from TDC to BDC, inlet valve open and train pipe air entered into the cylinder through VA1B control valve and vacuum reservoir. Piston travels from BDC to TDC, inlet valve closed and exhaust valve opens due to air pressure, evacuated through exhaust pipe into atmosphere hence vacuum created in train pipe.

To check the vacuum level in train pipe, vacuum gauge is providing on both control desk. Vacuum check valve is connected with vacuum reservoir to maintain the certain level of vacuum in expresser sump. Oil coming with smoke from expresser exhaust pipe

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