Traction motor blower bearing improves reliability

Routine maintenance is important to keep vital assets functioning reliably. This is especially true for the rail industry, which needs rolling stock to operate continuously between service intervals. 

By using the feedback provided by Sulzer, one operator eliminated a problem with blower units overheating and reduced maintenance costs at the same time.

As with many industries, the rail sector issues schedules and check lists to ensure all the necessary maintenance procedures are completed on time. 

However, in one case this process appears to have had a flaw. One of the items listed is the grease point for the blower motor bearing, but since this is hidden from view, it is difficult to determine the correct amount of grease required.

Regular maintenance

James Goulding, Service Centre Manager at Sulzer’s Sheffield Service Centre, explains: “The operator runs Class 91 locomotives with carriages that are each equipped with traction motors that have blowers fitted for cooling. Each carriage is regularly taken out of service for maintenance that is completed by Wabtec Faiveley, and the blower units are sent to our service center in Sheffield for overhaul.”

However, in addition to the regular maintenance items, Sulzer was also receiving blower units that had been changed due to an issue with overheating. 

In these cases, the failure of the blower motor had caused the traction motor to also overheat and need repairing. 

The rail operator holds spares of these components, so downtime was minimised, but Sulzer had the task of repairing the blowers and finding the cause.

When the blower motors were stripped down, the Sulzer engineers noticed an excessive build-up of grease in the motor casing, which almost certainly contributed to the problem. It appeared that, while the frequency of greasing may have been correct, the amount of grease applied was not being properly regulated.

Recommended solution

Reports stating the cause of the failure were sent to Wabtec Faiveley, who referred Sulzer’s findings back to the rail operator and discussed the proposed changes. At the same time, Sulzer also recommended the implementation of a ‘sealed-for-life’ bearing that would not need greasing. The bearing dimensions would remain the same but some changes would be required to the fan design.

The rail industry however, does not implement engineering design changes without following set procedures that ensure safety is maintained. Wabtec Faiveley carried out reliability testing for six months to prove the Sulzer design change before it would be applied to the fleet.

Once these had been completed, and the operator was satisfied with the improved design, the operator and maintainer setup a baseline regime to overhaul 124 units. 

The rolling repair programme ensured the new bearing design was fitted to each motor as part of its routine maintenance overhaul. 

In addition, when the new bearing was installed, Sulzer also blanked off the original grease line to prevent any accidental greasing of the new bearing.

Carl Chambers, Senior Projects Manager for Wabtec Faiveley, comments: “It is important that we deliver the best service to our customers and we have worked closely with Sulzer to deliver the optimum solution. We have certainly improved the reliability of the blowers and reduced maintenance costs for the operator.”

James Goulding concludes: “Since the change in bearing design was implemented, the issue with blower motors overheating has been resolved. This has greatly reduced the number of components being removed from service outside the normal maintenance intervals. Together with the optimized maintenance routine, the operator has seen a significant reduction in running costs.”