Train parting is an unforeseen division of a train into two or more portions while the train is on run or just about to move. Train Parting is a common unusual occurrenceTrain parting is an unforeseen division of a train into two or more portions while the train is on run or just about to move. Train Parting is a common unusual occurrence affecting train movement adversely.

Types of Train Parting and their causes:

Train parting is classified under two main heads.

Vertical Parting:

Vertical parting takes place due to excessive CBC height variation. The main reasons for variation in CBC height are:

  1. Loose/ low rail joints
  2. Mud pumping under the rail joints
  3. CBC drooping– excessive wear and tear of coupler shanks and striker casting/ bearing piece.
  4. Excessive overloading in the wagons.
Horizontal Parting:

Horizontal train parting takes place due to following reasons:

  1. Uncoupling of CBC.
  2. Breakage/ wear of CBC components due to inherent defects.
  3. Failure of draft gear
  4. Bad engineman ship

The most common causes of train parting are uncoupling of CBC on run (without any breakage of any parts), breakage of knuckle failure of draft gear and working out of CBC. The reasons for uncoupling and preventive measures taken to avoid uncoupling are described as under :

Lock not properly engaged: In most of the cases, the lock does not drop down to the full locked position inside the coupler head. This may result in slipping up of the lock during run causing uncouplingIneffective anti-creep device.The lock may slip up due to jerking and jolting during the run if the anti-creep feature is not effective.

Operating handle dropping on run.This is caused by breakage of supporting bracket resulting in operating handle falling down on run and hitting the ballast. This tends to turn the handle leading to the lifting of the lock piece and uncoupling.

The excessive play between the anti-rotation lug and bearing piece slot:

Due to excessive play between the anti-rotation lug and bearing piece slot, the operating handle can operate on the run due to jerks and can cause uncoupling. Anti-rotation lug is made out of square cross-section MS bar with standard dimensions of 16 mm x 16 mm and slot width bearing piece of 17.5 mm.

Unauthorized tampering with operating handle :

This is believed to be a common incidence by many Railways. Since uncoupling lever is situated alongside the wagon and is easily accessible, it is easily prone to unauthorize and mischievous manipulation.

Uncoupling due to vertical slipping out of knuckle :

This may occur due to abnormal relative vertical movement between the two coupler heads causing slippage of one knuckle out of the other. This situation is very unlikely to arise but there may be a possibility in the event of combination of the number of adverse factors like maximum difference in coupler heights & unevenness on rail joints.

BREAKAGE of CBC Components:

Breakage of knuckle

  • Breakage of lock
  • Breakage of coupler body
  • Breakage of yoke
  • Breakage of yoke pin
  • Breakage of coupling link
  • Breakage of operating handle bracket
  • Breakage of follower plates
  • Breakage of yoke pin support
  • Breakage of yoke pin support plate rivets
  • Breakage of coupling screw
  • Breakage of coupling link pin
  • Breakage of drawbar/drawbar hook

Material failure contributes to 75% of the breakages (approximately 50% of the total number of partings).  The remaining 25% is included as sudden shock loading of the couplers.

  • Material composition not according to specification
  • Blow holes/Air pockets in the castings
  • Slag inclusion in the casting
  • Improper heat treatment of CBC components (knuckles, CBC coupler body, and lock)
  1. Operating lever bent
  2. Operating lever escaped from bracket or dropped down with the bracket, Lifting up the lock on hitting the ballast
  3. Trespassers interfering with CBC operating handle
  4. Improper locking of CBC
  5. Failure of anti-creep mechanism
OPERATING DEFECTS (poor engineman ship):
  • Sudden notching up, sudden application of brake from rear(May cause wheel slip)
  • Sudden notching up, after brake application ( jerk on knuckle, poor engineman ship)
  • Sudden notching up at signals
  • Loco trouble( break suddenly applied in front of vehicle and rear vehicle is under deceleration)
OTHER REASONS (Miscellaneous):
  • Muddy Track (CBC height varied)
  • Uneven Track (CBC height varied)
  • Overloading or uneven loading (CBC height varied)
  • Improper marshaling ( 4-wheeler empty wagon marshaled between two bogie stock may vary the CBC height during run) Loose/low rail joints Hump/ lose shunting, etc

Reasons for Breakage of coupling or uncoupling due to Jerk/excessive tractive effort:

The main reason for breakage of coupling is jerk due to an excessive tractive effort, pulling forces & pushing forces. The reasons for jerk are spring slack & free slack. Spring slack occurs due to compression of Draft gear at the time of braking. The limit of maximum spring slack is 5″, the free slack occurs due to an excessive gap between couplers which is approx. 1″.

The jerk is developed :
  • By drivers during run due to improper driving technique
  • Due to the defect in loco such as wheel slip, Power Ground earth fault or shutting down of the engine due to other reasons.
  • Application of Brake by banker pilot or by Guard during running.
Reasons for Generation of Jerk by Loco Pilot :
  • The sudden opening of Throttle notches.
  • Emergency Braking
  • Traction Power Cutting off
  • Faulty train operation on Gradient
Measures to avoid Train Parting:

The Loco Pilots have an important role to play in preventing the train parting cases. Good driving skill is very important. Some of the guidelines useful for drivers are given as under :

It is observed that additional shock load comes on the coupler when drivers apply traction before the full release of brakesStarting of goods train after stopping-wait for minimum 3 minutes in case of air brake train release the brakes. (Ref. RDSO’s Report No. MP.Misc-88/99 REV-0.01)Avoid jerky movement during starting and stopping train while attaching the loco on to the formation, attach with a little bump and push the formation back by about two meters to ensure that partially lifted locks drop into position.

Then, pull the train ahead by half-a wagon length, to identify the CBC which are not locked. In the process, fouling mark should not be infringed.While starting a train, the notching up shall be gradual as to have smooth run out and thereby avoid the shock loading of CBCs.

At enroute stations, LC gates, signals etc when the train is stopped for a long time the driver shall push back the train about two meters to ensure proper locking of CBCs which, might have been meddled with by trespassers/miscreants.While negotiating gradients, camel humps, maintain uniform speed, till the train passes the section.

Before negotiating an ascending or descending gradient, attain the critical speed necessary to negotiate the section, so that uniform speed can be maintained while passing over the graded section after application of brake, sufficient time shall be given for the release of brakes on the entire formation, before accelerating.

When continuous wheel slip is experienced, reduce the speed of the train, to avoid shock loading of CBCs.There shall be proper co-ordination between the leading driver and banker driver while negotiating the up-gradient in that section.

Measures to Avoid Jerks:

At Level:

Ensure that all couplings are correctly fitted. For this, Push the train back for about ½ wagon length so that all the couplings are coupled properly.Ensure that brakes of the train are fully released, for ensuring this, time should be given for releasing the brakes. Sufficient B.P. pressure should be ensured and air flow indicator should be in the constant position.Release the loco brakes after waiting for 10 seconds after opening of the throttle.

  • Release the train brakes before opening the throttle
  • Open 2-3 notches by throttle
  • Release Loco brakes
  • On starting of the train, open the throttle notch by notch precisely by keeping eye on needle of load meter.
  • Reduce the throttle notches in case of wheel slip.
  • If Banker engine is attached, driver of Banker engine should first open notches.
Down Gradient:
  1. Release Loco Brakes
  2. Allow train to move forward and attain the desired speed
  3. Use dynamic Brakes if required
On Sag:
  1. Open the notches
  2. Release the loco Brakes and open 1-2 Notches
  3. When the full train comes in a stretch, advance the notches, one by one by observing load meter.
Undulating Gradient:
  1. Open 1st Notch
  2. Release the Loco Brakes
  3. When the train started, open the second notch and when a meter is stabilized, open the notches as desired.
On Hump:
  1. Release train Brakes before opening of throttle
  2. Open 2-3 Notches by throttle
  3. Release Loco Brakes
  4. On starting of train, open the throttle precisely notch by notch observing needle of the load meter
  5. Reduce throttle notches when wheel slip experienced
  6. In case of banker engine, the banker driver should first open the notches
On Run of Train:
  • Open notches one by one
  • To control the speed of the train by the dynamic brake, apply air brake in train A-9 for bunching the load.
  • During Dynamic braking advance selector slowly and releasing should also be ensured slowly
  • Reduce the notches on up gradient during wheel slip
  • Sufficient releasing time must be ensured for full releasing of the load after application of brakes.
  • Advance the throttle for increasing the speed only after full releasing of load
  • Do not use loco brakes in running train
  • Keep watch over the Air flow indicator during running
  • Do not apply brakes suddenly
  • Do not open notches suddenly
  • Keep contact with Guard/banker Pilot on walkie talkie
  • Running of train should be ensured properly on Gradients
  • Do not use Loco brake in conjunction braking as far as possible during first brake application
At the time of Application of break in train :
  • Apply brakes properly
  • After Dynamic braking, notches should be taken after suitable gap
  • After stopping the train, B.P. Pressure recreation must be ensured.
  • On upgradient, try to stop the train on some notches and after stopping of train apply loco brakes.
  • Apply loco brakes after stopping the train
Attention by the Guard and Operating /Yard Staff:
  • During shunting, keep both the knuckles in open position.
  • Couple CBC stocks with a little bump.
  • Ensure the knuckles are locked, after shunting.
  • Marshal loaded stock in front and empty stock in rear always.
  • Do not allow empty stock in between loaded stock.
  • Do not exceed the tonnage of the train than the authorized limit.
  • Reducing of train tonnage than the authorized limit may be considered during monsoon/bad weather on the section where heavy wheel slip is experienced.
  • If any CBC defect is noticed in front of C&W staff, immediately advise for its rectification, without delay.
  • Avoid stopping of trains at unscheduled places, where cases of trespassing are possible.
  • Take off signals well in advance for the approach of the train.
  • Avoid taking off or putting off signals, as soon as the train reaches the signals.
  • Avoid stopping the train at signals situated on up gradients.
  • Do work the train with a free and relaxed mind.
  • Don’t open and close throttle frequently.
  • Do aware of the caution spot, and control your train well in advance.