[IRFCA] Brake systems used by IR.pdf

25/06/2015 [IRFCA] Brake systems used by IR

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Comparison of air brakes and vacuum brakes

Parameter Air Brakes Vacuum Brakes

Principleofworking

The compressed air is used for obtaining brake application. The brake pipeand feed pipe run throughout the length of the coach. Brake pipe and feedpipe on consecutive coaches in the train are coupled to one another bymeans of respective hose couplings to form a continuous air passage fromthe locomotive to the rear end of the train. The compressed air is suppliedto the brake pipe and feed pipe from the locomotive. The magnitude ofbraking force increases in steps with the corresponding reduction in brakepipe pressure and viceversa.

The vacuum brake system derives its brake force from theatmospheric pressure acting on the lower side of the pistonin the vacuum brake cylinder while a vacuum is maintainedabove the piston. The train pipe runs throughout the lengthof the coach and connected with consecutive coaches byhose coupling. The vacuum is created in the train pipe andthe vacuum cylinder by the ejector or exhauster mountedon the locomotive.

PressureEffective cylinder pressure = 3.8kg/cmFeed pipe 6kg/cmBrake pipe 5kg/cm

Effective pressure on piston 0.kg/cmNominal vacuum on train pipe 510mm.

Pipediameter

Feed pipe & 25 BoreBrake pipe & 25 Bore Train pipe & 50 Bore

Components of air brake and vacuum brake systems

Air Brakes Vacuum Brakes

Brake pipe and feed pipe (twin pipe system for coaching stock, singlepipe system for goods stock). Train pipe single pipe

Air brake cylinder 355mm dia Vacuum brake cylinder 24" type 'F'

Distributor Valve

Passenger Emergency Alarm Signal Device Alarm chain apparatus

Passenger Emergency Valve Clappet Valve

Guard's Emergency Valve Guard's Van Valve

Slack Adjuster Slack Adjuster

Direct Admission Valve

Hose coupling for brake pipe and feed pipe Hose coupling for train pipe

Auxiliary reservoir 100 l capacity Vacuum reservoir 320 l capacity

Cut off Angle cock

Check valve with choke

Dirt collector

Advantages of air brakes over vacuum brakes

Parameters Air Brakes Vacuum Brakes

Emergency braking distance (4500 tlevel track, 65 kmph) 632m 1097m

Brake power fading No fading At least by 20%

Weight of equipment per wagon(approx.) 275kg 700kg

Pressure Gradient No appreciable difference in air pressure between locomotiveand brake van up to 2000m.

Steep reduction in vacuum in trainslonger than 600m.

Preparation time in departure yards (45BOX or 58 BOXN) Less than 40 minutes. Up to 4 hours.

Safety on down gradients Very safe Needs additional precautions

Overall reliability Very good Satisfactory

Schematic diagrams

Singlepipe System

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Twinpipe System

Comparison of single‐pipe and twin‐pipe systems

Parameters Single Pipe Twin Pipe

Principle ofoperation

The operation is sameas that of the twin pipesystem except that theauxiliary reservoir ischarged through theD.V. instead of feedpipe, since there is nofeed pipe in single pipesystem.

The Brake pipe is charged to 5kg/cm by the driver's brake valve. The auxiliary reservoir is charged by thefeed pipe at 6kg/cm through a check valve and choke. The brake cylinder is connected to the atmospherethrough a hole in the D.V. when brakes are under fully released condition. To apply brakes, the driver movesautomatic brake valve handle either in steps for a graduated application or in one stroke to the extremeposition for emergency application. By this movement the brake pipe pressure is reduced and the pressuredifferenced is sensed by the D.V. against the reference pressure locked in the control reservoir. Air from theauxiliary reservoir enter the brake cylinder and the brakes are applied.At the time of release the air in thebrake cylinder is vented progressively depending upon the increase in the brake pipe pressure. When thebrake pipe pressure reaches 4.8kg/cm the brake cylinder is completely exhausted and brakes are fullyreleased.

Chargingauxiliaryreservoir

Discontinued duringbrake application Uninterrupted

B.C. andA.R.pressureequalisation

Occurs duringprolonged brakeapplication

Does not occur

Release ofbrakes(reductionin brakecylinderpressure)

Proportionate to buildup of A.R pressure Auxiliary reservoir is continuously charged through feed pipe

Leakage inbrakecylinderduringapplication

During emergencyapplication, feed forauxiliary reservoirfrom brake pipe isdiscontinued. Leakagesin brake cylinder willtherefore reducebraking force sinceauxiliary reservoir may

Auxiliary reservoir is continuously charged through feed pipe and hence leakages in brake cylinder can beequalised even during emergency application ensuring full brake force.

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not be able to equalisethe leakages.

Colour Brake pipe GreenFeed pipe White

Pressure Brake pipe 5kg/cm Brake pipe 5kg/cmFeed pipe 6kg/cm

Comparison of conventional and bogie‐mounted air brakes

Parameters Conventional Air Brakes Bogiemounted Air Brakes

Bogie cylinder mounting location Underframe Bogie frame

No. of air brake cylinders / coach 2 4

Size of cylinder 14" 8"

Slack adjuster External Integral with the air brake cylinder

Brake block Conventional High friction 'K' type composite block

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[IRFCA] Brake systems used by IR.pdf

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