The rail industry places very high demands on the components used within it. Meeting the requirements, NTN-SNR Group has for many years been providing bearings for this industry, where they have been used on vehicles ranging from freight trains and trams to high-speed trains
For over a century, NTN-SNR Group has been manufacturing bearings for a diverse variety of markets, and during this time it has become well known as a supplier of specialist products to the railway industry – particularly bearings for high-speed trains.
The rail industry is growing, with the European market set to grow steadily for many years, and NTN-SNR is planning to increase its sales in this area by a factor of three over the next six years. In fact, the Group is investing 14million Euros in a new production line specifically dedicated to manufacturing railway bearings. This will be located in Seynod (Haute-Savoie, France) and will be its third production unit dedicated to this sector.
The company is also going to increase the number of countries it sells into, and is working to gain more specific Approvals (HPQ and GOST) which are needed to supply into some markets/countries. Furthermore, it is intending to expand its range into more applications, and already with IRIS and COFRAC certifications has the ability to independently homolegate (certify) its bearings for certain load/speed regimes using its own test rigs.
Companies manufacturing for the rail sector need to ensure the components they produce meet the high reliability levels demanded – including withstanding harsh environmental conditions ranging from extremes of temperature to high speeds. Meeting these requirements, NTN-SNR has supplied bearings for many rail programmes throughout the world, including to both the Shinkansen in Japan (a network of high-speed railway lines) and the TGV in France.
In 1958, NTN began designing and developing high speed axle bearings for the dream train which would connect Tokyo and Osaka – covering a distance of 550km in just three hours. Six years later, the 0-Series, the first high-speed train in the world, entered service with a cruising speed of 210kph. Since then there have been a number of models, including the Shinkansen N 700 Series with a cruising speed of almost 300kph. The fleet of Shinkansen trains transports more than 200,000 people and makes the equivalent of ten round-the-world trips every day. The next generation of high speed train is planned to have a cruising speed of 400kph and NTN continues to be a key developer in this programme.
From the beginning of the design phases of the French high-speed train, SNR has been a partner in the development of the axle and transmission
bearings, and in 1981 the first French high-speed train entered operational service between Paris and Lyon with a cruising speed of 260kph. In that year, TGV N°016 beat the previous rail speed record, reaching a top speed of 380kph. SNR has been a key partner in all of the design phases of the bearings for the TGV and the production standard SNR axle bearings delivered to the TGV assembly line were the same as those used in the high-speed train that shattered the world rail speed record on 3rd April 2007, reaching a top speed of 574.8 kph (357.2 mph).
For high-speed trains, the company has designed the main drive bearings for axle, motor and transmission applications. Here, the need for high speed and reliability means special attention is necessary when it comes to producing specific bearings – vibrations, shocks and temperature control in axle bearings; electrical damage and corrosion in traction motor bearings; poor lubrication in extreme cold temperatures; and high accelerations in transmission bearings.
Due to the safety critical nature of components for high-speed transport, particularly axle-bearings, SNR developed a specific high speed bearing, with optimised internal geometry that uses the highest quality materials for maximum reliability.
For the high speed axle bearings, the company spent time focusing on the areas inside the bearings where heat is generated, and optimised the design to minimise this heat. For the record-breaking journey, the normal bearing operating temperature rose only by 10°C when the bearing was running at twice the normal speed.
Outside of high-speed applications, the company has also produced bearings and axle boxes for less demanding applications – such as Intercity, locomotive and freight trains, metros and trams.
Changes in European regulations have created more interest in instrumented bearings, and to provide a solution for these requirements NTN-SNR is developing sensors for axle bearings capable of measuring temperature, speed and vibration levels. The new railway axle bearings will give operators the possibility of replacing existing sensors with a modern, reliable and compact version. The signals provided will give accurate information in order to optimise maintenance and replacement cycles and thereby reduce overall operating costs.
Innovation is also being applied to traction motor bearings. Here the electrical current present in the motor can produce electrical pitting in bearings and corrosion, causing damage and premature failure of the raceway and rolling elements. NTN-SNR has developed an insulated bearing range, the Megaohm series, which protects from electrical damage. All trains in Japan have been equipped with this technology since 1994. There are two options available here: Ceramic – the bearing is treated externally with a sandwich of materials in order to provide electrical insulation; and Resin – which provides an insulating film on external surfaces.
With the railway industry a growing area, producing components that meet all the design challenges is essential to ensuring both reliability and safety.
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