Sub:-  CTRB  & Roller Bearing Maintenance practices.

        Recent failure of Loco No. WDP₄ 20016 due to CTRB, failure has highlighted the need to ensure proper examination of CTRB. 

Trip examination

1.    Predictive maintenance – Measure CTRB temperature of each wheel both ends quickly with non-contact type laser temperature gun.

        Readings are best taken in yard. All readings must be taken quickly at identical location in axle box & it should be checked that temperature readings are not vitiated due to effect of sun on one side of axle box in stationary loco.

        Though practice of temperature recording has been started in sheds, interpretation of result & corrective action is lacking in most of sheds.

2.    Periodical measurement in yard/mainline fueling point should be organized.

3.    O.E.M. recommends change of bearing, when it becomes difficult to touch bearings by hand or if bearing temperature is more than 90⁰ Centigrade.

 As these are limiting rejection criteria and bearings will be irreversibly damaged in line most probably before loco touching the shed, it is necessary to use predictive maintenance technique to predict impending failure before actual failure in line.

4.    Temperature difference across each wheel should not exceed 3-4⁰ C. Temperature difference between any two axle-boxes should not exceed  7-8⁰ C. If excess temperature difference is observed than axle box should be examined for unusual rise in temperature.

5.    During trip examination, under-gear checking staff & wheel gauger should be trained to look for broken back cover bolt, oozing out of grease. Wheel/axle box should be replaced in case of any irregularity  noticed.

6.    If no fault is noticed in shed despite higher temperature difference is obtained, then one staff should be booked in footplate along with temperature gun to record the temperature after 100, 200, 300 km of run. 

7.    If no variation in temperature rise is observed than loco can be permitted to run, if higher variation > 9⁰ C is obtained then wheel requires to be replaced.

Axle box maintenance/ in shed.

1.  Axle box attention is shed should be avoided. CTRB should be sent to workshop for overhauling as per periodicity laid down by O.E.M.(6 years)

2.    No overdue Axle box should be permitted in service. Date of OVH should be painted in axle box cover for case of identification.

3.    Any wear or damage to end cap or packing is an indication that adapter has been out of position & bearing may have sustained damage. Bearings having external parts visibly cracked, damaged or bent must be removed from service.

4.     Wheels must be free from built up deposition trend & several slid flats.

5.    Use temperature indicating acrylic strip/crayon of 90⁰ centigrade; if it is found black then bearing must be removed from service.

Tell tale signs for identifying defective CTRB

1.    Loose backing ring. A backing ring that can be rotated by hand is considered as loose.

2.    Loose, cocked or visibly damaged, grease seal of the cartridge tempered roller bearing.

3.    Missing cap screws or missing locking plate.

4.    Grease leakage between cup counter bore & seal may be an indication of loose seal. Grease leakage between the backing ring & axle fitted radius is an indicator of loose backing ring & must be removed.

5.    RDSO has identified less torque value for tightening axle cap screw as one of the most probable cause of failure. Axle cap screws must be tightened to a torque of 420 ft-lbs. As a special drive all existing EMD locos must be tightened with revised torque value ( RDSO Instruction Bulletin No.MP.IB.VL-08.30.09   (Rev 00).

6.    Mounted end play (MEP) should be measured by using magnetic base dial indicator. If the bearing end play is less than .001” or more than .015 ”. Bearing should be removed.

7.    After conducting UST of axle as per the recommended procedure, apply a new locking plate and tighten all axle cap  screws to a torque value of 420 ft. lbs using a suitable torque wrench which must be accurate within ± 4%.

8.    Check for Noise(Rough Ride Check)

a.    On rotation by hand, the noise produced, if any, should be interpreted as follows:

·         Hissing: Hissing noise is normal. This noise is basically generated due to running of seals on the seal wear ring.

·         Rattling: Rattling noise is also normal.  It is due to hitting of roller to the cage pocket during running.

·         Cyclic: If the noise is cyclic and abnormal, bearing should be removed from service.

9.    Checking proper seating of CTRBs.

It should be checked by inserting a feeler gauge inside the backing ring.           A 0.0025” feeler should not go in.

10.              Adapter examination:

·               Cracked or broken adapters must be scrapped. Repair by weld or brazing is not permitted.

·               Warped, twisted or distorted adapters must be scrapped.

·               Worn Adapters, adapters having groove, not meeting gauge specification must be scrapped.

·               If wear on both sides exceeds 1/8” (3 mm), adapter should not be reused.

                 Shed should identify overdue and defective CTRBs running in service and make an action plan to replace/overhaul them on priority.