NSK extends the service life of its wheelset bearings

Tony Synnott, NSK European Railway Sector Manager based at the NSK factory in Newark, Nottinghamshire comments on the work done so far to achieve the lifecycle targets: "Put simply, 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 essential to the continued running of the train. What we have 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 we use 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 and other elements out. The lubricant we are using 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.

Tony Synnott continues: "Life Cycle Costing (LCC) is very important to Hitachi. The bearings will run for a 6-year period and be re-lubricated just once, coinciding with wheel maintenance. This equates to over 1 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 we can reduce maintenance time and avoid additional assembly and disassembly work, which is tough on components, some of which are press-fit items."

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.

Key drivers to the rail market worldwide

It is worth confirming that investment in rail networks globally is increasing and this is helping provide manufacturers with the confidence to invest in developing new trains with more advanced propulsion systems.

Cost of operations, reliability and reduced environmental impact are dominating the political, practical and technological decisions that are being made now. The Intercity Express Programme (IEP) project in the UK is a good representation of what we can see happening in other territories. Electrification is increasing for both inner city and inter-city rail transport solutions; however, dual-power is also very important to bridge the gap between electrification projects and provide back-up power in operation.

Since the push towards fuel efficiency and reduced emissions is leading towards electrification, technology investment is being directed towards managing dual-power changeover control to ensure it is smooth and efficient. Work is also being done on making the electric motors as powerful and compact as possible, much in the same way as hybridisation is happening in passenger cars and other road vehicles.

Ensuring long service life and ultimate reliability for the wheel and traction motor bearings - another component NSK supplies worldwide, is absolutely vital for both the manufacturers and the operators who are responsible for the maintenance and support of the trains in operation on long contracts.

The profitability of a project as a whole can be dependent on the train's reliability and for the operators who are demanding reliability there is pressure to hit their own targets for on-time on-schedule journeys. For example, NSK supplies a large proportion of the London Underground trains with traction motor bearings, designed to deliver the ultimate in reliability.

Bearings are responsible for the reliability and efficiency of a great many components in a modern train, not least the wheels and electric drive motors; this covers many ancillary components from pumps and compressors to actuators and air conditioning units. NSK is working on reducing the rolling resistance of many bearings, particularly in vehicle applications where any reduction provides a corresponding boost in fuel efficiency; the company is also looking at reducing noise and delivering sealed-for-life products that provide the ultimate in terms of zero maintenance throughout the design life of the component.

To learn more about NSK wheelset bearings, please go to www.nskeurope.com.