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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