Refurbishment of tilt bearings for Pendolino trains

The yoke-type track roller, which was custom designed by Schaeffler in the early 1990s specifically for use on the Pendolino train, is part of a yoke-type track roller unit that is used on the coach body tilting system. In conjunction with the rails, the yoke-type track roller units act as a roller-supported cradle system, which allows the coach body to tilt into bends in the track in such a way that the direction of the coach body axis matches the resulting acceleration.

The yoke type track roller unit complete or "Tilt Roller Bearing" comprises two bearing assemblies, a bespoke split core resilient bushes and a two-part tilt roller housing. The built-up assembly is bolted to the bogie frame - two per bogie - these provide the base dynamic stability for the profiled and hardened "tilting shapes' to travel over when the train is operating in tilting mode. Without the robust and reliable tilt roller yoke bearings, the key tilting capability of the class 390 Pendolino would not be able to operate. The yoke bearings are very reliable units and have performed consistently between overhauls.

Gary Timmings is Supply Chain Manager for Special Projects and Overhauls at Alstom in Wolverhampton and is responsible for managing material availability for the 60-week overhaul programme at Alstom's Repair Depot in Longsight, Manchester. He comments: "The tilting mechanism on a Pendolino train is a critical system as the train relies on this to enable it to operate at optimum speeds [up to 125mph] along the West Coast Mainline. It is essential that these systems operate reliably at all times because if they don't, this will have a detrimental effect on the overall operational performance of the train and on the efficiency of the West Coast Mainline. Alstom therefore operates a heavy overhaul maintenance regime on the tilting systems."

In March 2015, Alstom began overhauling the entire fleet of 56 Pendolino trains at Longsight. A critical part of this overhaul is the refurbishment of the yoke-type track rollers by Schaeffler. The 60-week programme involves the overhaul of a trainset worth of bogies per week (22 for an 11-car set and 18 for a nine-car set). Each bogie is fitted with four yoke-type track rollers per bogie, which means that every week Alstom engineers need to remove 88 or 72 yoke-type track roller units and send these to Schaeffler for refurbishment. The units are replaced with newly refurbished units from Schaeffler's Refurbishment Centre in Schweinfurt, Germany.

Timmings states: "Logistically, it's a very challenging overhaul programme. We are currently just over halfway through the project and the support from Schaeffler has been excellent. We've had no issues at all with any refurbished track rollers, both in terms of their quality and in the delivery of the units from Schweinfurt to our warehouse in Preston. The working relationship between Alstom and Schaeffler is very good and the whole process has been painless and trouble-free, which is important on large, critical overhaul programmes such as this one."

High-quality refurbishment

The double-row yoke-type track roller comprises a crowned outer ring, a full complement cylindrical roller set, inner ring, thrust washer, Lamellar ring, Nilos ring and retaining ring. The unit is sealed, greased and protected against corrosion.

At Schweinfurt, the refurbishment process involves dismantling the track rollers and 100 per cent visually inspecting all individual components for any signs of wear or damage, which can include fatigue, cracks, corrosion and indentations caused by overrolled particles. All the parts are then cleaned to remove grease, adhesive and dirt. Any defective contact rings are replaced with new ones. Outer and inner bore diameters are checked according to dimensional requirements. The units are then re-assembled, sealed, greased, packaged and returned to Alstom's warehouse in Preston.

Jeremy Spencer, Rail Sector Manager at Schaeffler UK comments: "For Alstom, the cost of having the track rollers refurbished by Schaeffler is lower than purchasing new replacement rollers. Due to the large volume of units involved in this programme, the overall cost is significantly lower. Furthermore, in terms of quality, a track roller refurbished by Schaeffler can be returned to the customer in an as-new condition. Refurbishment also has the additional advantage that it generates significantly lower CO2 emissions compared to the manufacture of new bearings, which means that the good environmental performance already achieved by the rail industry can be enhanced further."

The inspection and refurbishment process is to a high specification. Only fully qualified Schaeffler personnel in Schweinfurt are permitted to handle, inspect and repair the bearings.

Spencer continues: "Schaeffler's excellent performance on this project demonstrates that it can competently manage large rail bearing refurbishment programmes, without any disruption caused to the customer's maintenance, repair and overhaul programmes."

100 years' experience in rail

Schaeffler boasts more than 100 years' experience in the rail industry, with applications including axlebox bearings and housings; bearings and components for traction motors and gearboxes; railcar connectors; tilting technology; and bearings for train doors.

With increasingly complex operating demands and more strict safety standards in the rail industry, Schaeffler's test facilities in Schweinfurt provide customers with complete peace of mind. As Spencer states: "As well as refurbishments, we are able to conduct functional tests on complete assembled bearings, specific individual components, materials and lubricants. Test rig simulations can also be conducted on bearings, which help to contribute to significant increases in the service life and maintenance intervals of rolling bearings for a wide range of rail applications."

To learn more about rail refurbishment please visit www.schaeffler.co.uk.