PREVENTION OF INCIDENCE OF BRAKE BINDING

BY:

S.Singh,

Asst. Prof./C&W/IRIMEE

Brake binding is defined as the situation when the brake block is in contact with the wheel tread though the A-9 valve position is in released position.

The severity of the brake binding depends on the force exerted by the brake blocks on the wheel tread.

DEFINITION

Very often wheel skidding is wrongly interpreted as brake binding.

Though brake application quality in relation with the adhesion is the basic cause of wheel skidding, the incidence of wheel skidding must not be merged with the incidence of brake binding.

CONFUSION IN BRAKE BINDING

DEFECTS IN LOCOMOTIVE

DEFECTS IN TRAIN HANDLING

DEFECTS IN DISTRIBUTOR VALVE

DEFECTS IN BRAKE CYLINDER

DEFECTS IN DIRT COLLECTOR

DEFECTS IN SAB BRAKE REGULATOR

DEFECTS IN BRAKE GEAR

MAJOR CAUSES FOR BRAKE BINDING

Released position

BP BCCR

ATM ARBP

Application position

BP CR AR BC ATM

Brake cylinder pressure fails to communicate with atmosphere in after-application position

BRAKE BINDING CATEGORYPNEUMATIC

BP, CR, AR is communicated with brake cylinder in pre-application position

BRAKE BINDING CATEGORY

MECHANICAL

Brake gear components fail to retract to RELEASE position

DEFECTS IN LOCOMOTIVE Inspection of air system

Check for fluctuation in BP pressure

Check for moisture/oil / dirt content in compressed air.

MR CHARGING TIME:

Close the brake pipe cut out cock, place MU-2B valve in “Trail” position.

Keep both independent and automatic driver’s brake valve in release position.

Keep electro-pneumatic compressor, if available, in open position.

Keep toggle switch of the control stand in “On” position.

Start engine.

The charging time of MR up to 10 kg/cm2 at idle notch should not be more than 5 minutes for 506-litre reservoir, 6 minutes for 700-litre reservoir with 6CD4UC expressor and 3 minutes for 700-litre reservoir with KE-6 expressor.

EXPRESSOR CUT-IN TO CUT-OUT

Charging time for the pressure to build up from 8 to 10 kg/cm2 should not be more than 1 minute with 6CD4UC compressor and 35 seconds with KE-6 compressor for 700-litre reservoir

MR LEAKAGE:

Apply independent brake to 3.5 kg/cm2.

Shut down engine. Reduce MR to 6 kg/cm2.

Note drop in MR gauge. The leakage in MR should not be more than 0.2 kg/cm2 in 3 minutes.

Recharge the system with A-9 automatic brake handle in release position. Apply emergency brake application with A-9 valve.

Shut down engine. Reduce MR to 6 kg/cm2.

Note drop in MR gauge. The leakage in MR should not be more than 0.2 kg/cm2 in 3 minutes.

BP LEAKAGE:

Recharge the system with A-9 automatic brake handle in release position.

Make a 0.6-kg/cm2 reduction in brake pipe.

Close cutout cock. Move MU-2B control valve in trail position.

Note drop in BP gauge. The pressure drop should not exceed 0.7 kg/cm2 in 5 minutes.

DEFECTS IN TRAIN HANDLING

Releasing practice of brake

Wait for two minutes in coaching stock or three minutes in freight stock at least after moving brake valve handle to release position after emergency application.

Avoid extended application of the pressure surge to avoid over charging

DEFECTS IN TRAIN HANDLINGObserving air flow meter

Keep close watch in the airflow indicator to monitor incidence of excess leakage.

DEFECTS IN TRAIN HANDLINGObserving ampere meter

Keep close watch in the Ampere meter reading for current level

DEFECTS IN TRAIN HANDLING

Controlling miscreant activity

Keep vigilant on tampering DV isolating handle position

Keep vigilant on tampering handle of Cut off angle cock position

DEFECTS IN TRAIN HANDLING

Drainage of condensate

Drain condensate from air reservoir, oil separator and filter.

Open drain cock slowly so that condensate is carried out with the air.

DEFECTS RELATED TO DVMounting of DV on common pipe bracket

Check holes of common pipe bracket are one-to- matched with the corresponding location on the CPB seal.

Check collars provided on the CPB seals are uniformly projected.

Use small quantity of hard grease on CPB before positioning of the seal to avoid displacement while mounting.Check that release choke is clear.

FLOW OF BP/CR/AR TO BRAKE CYLINDER

Shifting of CPB seal

Isolating collars provided on the CPB seal cut

DEFECTS RELATED TO DV-contd..

DEFECTS RELATED TO DV-contd..Assembly of DV with Intermediate flange

Overhaul / Repair distributor valve with Intermediate flange as a single unit.Check holes of Intermediate flange seal are one –to – one matched with respective location in the distributor valve.Check collars provided on the seal are uniformly projected.

DEFECTS RELATED TO DV-contd..

Inspection of DV

Check the valve is free from rubber buldging or debonded for valve plate (10) in KE type or valve (37) in C3W type.

Check for smooth movement of hollow stem in its guide during assembly. This may be ascertained by the movement of hollow stem •Check that hollow stem is not bent.•Check that outer surface of the hollow stem is polished.

C3W TYPE DISTRIBUTOR VALVE - FLOW DIAGRAM

Defects related to DV-contd..

Inspection of DV

Apply light coat of thin grease on the hollow stem.

Check the condition of CPB filter. This is ascertained by:

Clean CPB filter in every schedule.

Clean vertical passage in CPB.

Defect in Brake cylinderInspection of brake cylinder

Check for breathing passage. This is ascertained by:Avoid greasing of Trunk during assembly.

Clean annular space between Trunk and Front cover.

Defects in Dirt collector

Inspection of dirt collector

Condition of outlet passage. This is ascertained by cleaning Dirt collector in every schedule.

Defects in SAB brake regulator

Inspection of Barrel

Check that the barrel has no dent.

Confirm that Traction sleeve passes smoothly inside the entire length barrel during assembly.

Defects in SAB brake regulator-contd..Inspection of Adjuster nut

Check axial play of the Adjuster nut with the spindle. Since actual measurement is difficult, excessive play must be felt while assembly.

Make sure that the adjuster nut falls freely along the spindle when held vertical.

Defects in Brake gearAdjustment of brake gear

Adjust end pull rod hole and maintain length of pull rod such that the Equalising levers be in near vertical in brake applied position.

Defects in Brake gear-contd..Inspection of Equalising lever

Ensure that the Z-lever pins used with Equalising levers are polished.Ensure the corresponding bushes are without any oblong deformation.Radial clearance is maintained within 0.75 mm.

Defects in Brake gear-contd..Inspection of Actuating rod

Ensure that the Actuating rod is not twisted. The straightness is realised by smooth fitment of the Actuating rod with the both Equalising levers with the pins.

Some thoughts on Wheel Skidding

Incidence of wheel skidding depends on Brake cylinder pressureBrake cylinder diameterBrake rigging leverageNominal static loadCantLow jointTwistCurvature

Dry/wet condition

Surface condition

Normal wheel reaction

Length of transition curve

Vehicle suspension

Vehicle speed

Tractive force

Acceleration/Retardation

Wheel gauge

Wheel base

Position of centre of gravity of the vehicle

Flange angle

Mass moment of inertia of wheel

Position of tractive point on the wheel

Coefficient of friction between wheel and brake block

Coefficient of friction between wheel and rail

Sliding velocity

Initial speed of braking

Temperature rise

WHEEL TO ROLL OR TO SLIDE

Tractive effort applied to accelerate the vehicle in fully released condition:

 

2N < P > (32N)

Brake applied to wheel to stop/retard the vehicle

 

FB ≤ (3/4)(2/1) N

Tractive effort applied to cause motion in brake binded condition

FB ≤ (1/2)(2/1) N

P ≥ (32N - 41 FB)

It implies that if more than 25% braking forces is released in partial brake binding, It is possible to roll the wheel with just adequate tractive force.

Increase in tractive force will cause skidding in partially binded wheel

Thank you