One million mile bearings

NSK bearings have been fitted to the first batch of Hitachi trains and are set to play a vital role in ensuring the trains built for the Intercity Express Programme (IEP) meet targets for minimum maintenance, high reliability and extended service life.

Based on designs that have delivered in terms of performance and safety on the advanced high-speed Shinkansen trains in Japan, the NSK wheelset bearings have been engineered to match the operating life of the wheels themselves, which is over one million miles. 

The wheelset bearings are the interface between the static parts of a train’s undercarriage and the rotating parts, including the power transmission and wheels. Their performance and reliability are clearly essential to the continued running of the train. 

What NSK has done with this project is to adapt some of the aspects of the designs which have worked extremely well in Japan and extend the maintenance requirements to coincide with wheel maintenance, thereby guaranteeing performance, while increasing train availability.

The working environment is extremely tough for these double-row taper rolling bearings, with high loads and lots of potential external contaminants present, plus temperature differentials and constant vibration.

The steel used to manufacture the races, for example, has been developed by NSK purely for extended life in bearings used for extreme conditions. The sealing arrangement and materials are also critical to keeping the grease fresh inside the bearing assembly - and contaminants at bay. The lubricant used for these bearings is of the highest quality and formulated specifically for this application.

Agility Trains, supplied by Hitachi Rail Europe will provide 122 new electric and bi-mode trains, for both the Great Western Main Line and the East Coast Main Line, manufactured in a new state-of-the-art manufacturing facility in the Northeast of England. The remaining trains will be manufactured for service between 2016 and 2018.

Life cycle costing is very important to Hitachi. The bearings will run for a six year period and be re-lubricated just once, coinciding with wheel maintenance. This equates to over one million miles of operation.

Bearing maintenance in the past was conducted prior to the wheel maintenance, which meant removing the wheel twice. By synchronising with the maintenance period of the wheel, maintenance time is reduced and additional assembly and disassembly work (which is tough on components, some of which are press-fit items) is avoided.

There is a 30 year commitment from NSK to Hitachi and Agility Trains in order to deliver this project, incorporating 27 years of contractual service support in addition to the development, test and build process. Since NSK will be celebrating its 100th year anniversary in 2016 it is well placed to instil confidence as a long-term project supplier.

Tony Synnott is NSK's European railway sector manager based in the UK