bearing failure on coke cart

Bearing Failure Analyses on Coke Car

Liam McCabeMechanical Summer Placement 2016Morfa Coke Ovens22/09/2016

Table of contents

Table of ContentsIntroduction....................................................................................................................2Analyses.........................................................................................................................2Proposals.......................................................................................................................2Next Steps......................................................................................................................2References.....................................................................................................................2Appendicies...................................................................................................................3Appendix A.....................................................................................................................4Appendix B.....................................................................................................................5

AbstractThis report provides an overview of the recent bearing failure on the Coke Car.

This is a re-occurring failure where the bearing isn’t fulfilling its recommended service life. An explanation is given on the failure, the possible failure modes which have been explored and how they were ruled out, the analyses of the bearing, final conclusions of the failure mode and the next steps to ensure Coke Car bearings last their service life. This reduction of failures will have a cost saving benefit through part costs as well as the costs associated through a “shuffle” of cars.

AcknowledgmentsI would like to thank the help and guidance of Dean Reynolds, Rotational

specialist for Brammer in assisting with this analyses and Sean Peat, Service Engineer from Timken Bearings for producing the report on the failure analyses of which this report relies heavily upon.

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IntroductionOn the 8 of July 2016 the north east side bearing on the Coke Car failed

dramatically. This follows two other failures of a similar fashion within the past two years on both Coke Car, in all 3 situations leaving the respective Coke Car out of use until a replacement is fitted. These failures have all occurred notably before the service life of the bearings providing the need for an investigation.

AnalysesThe current bearing is a TIMKEN HM133444 – 90239 double roller tapered

type. It is fitted to the axle via an interference fit with a difference of internal diameter of 0.082 with an axle tolerance of ±0.002mm. The operation the bearing is involved in includes high, uneven loads, high temperatures, steam presence, and thermal and load cycling of high difference and frequency.

From analyzing the drawing of the axle (see appendix a) and comparing it to the manufacturers axle specification (see appendix b), the tolerances are out or the diameters actual and specified. The diameter of the axle used is 157.234mm-157.230mm and what Timken specifies is 157.264mm-157.238mm. This loose fit can lead to wear and heat due to relative motion between moving parts causing fretting. This fretting generates fine metal particles which accelerate this process of loosening and damaging the parts (Barden Precision Bearings (Unknown).

From consulting one of Timken’s service engineers along with a Brammer rotational specialist, this was found to be the main cause of the failure because of heavy wear on rollers and race as well as “heavy metal particle contamination”. Other modes of failure mentioned include heavy impact which could be due to the un-clean coke car track. (Peat, S. 2016).

ProposalsThe proposed improvement to prevent this premature failure reoccurring is to re

–order the correct sized axle for the bearing being used to ensure a suitable interference fit. This will reduce roll wear and increase the service life of the bearing. The costs incurred of ordering new axles will be offset as every failure which occurs (approximately 2 a year) damages the axle beyond use as well as the bearing and end cap.

The possibility of impact having caused the damage, most likely due to waste on the track will be addressed in another project looking to improve the state of the track to make it consistently clean.

Next StepsFollowing this failure analyses project, the next step is to continuously record if

any future failures occur before the service life again. If this does occur, then the causes which are familiar with this failure should be compared. If they compare, then the proposals for improvements should be reviewed again and if appropriate re-investigate the failure.

ReferencesUnknown. (Unknown). Bearing Failrue: Causes and Cures. Unknown: Barden Precisions Bearings.

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Peat, S. (2016). MCO Coke Car Brg Report 08 16. Coventry: Timken.

Appendices

Appendix A- Drawing no. 1816.37.02.12.003, drawing of axle used on Coke Car with dimensions shown

Appendix B- Timken guide of AP Bearing for industrial applications, pg. 31

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Appendix A- drawing of axle used on Coke Car

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Appendix B- Timken guide of AP Bearing for industrial applications, pg. 31

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bearing failure on coke cart

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