SKF at Innotrans: Component care optimises service life in rail vehicles

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    2016 September 22, 13:00 CEST

    Stewart McLellan, Business Development Manager for SKF’s Railway Segment, explains how OEMs and rail operators can improve the overhaul, repair and replacement of critical components on rail vehicles, to extend service intervals.

    An industry trend for improved availability and performance of rolling stock has forced train manufacturers to find long life integrated products – as defined by the RAMS (Reliability, Availability, Maintainability, Safety) process. One important area of consideration is to extend service intervals – which boosts the availability of rolling stock while minimising the time spent maintaining and repairing it over its lifespan.

    Monitoring conditions
    A carefully planned condition monitoring strategy is an essential requirement if service intervals and component operating life are to be extended. On-line condition monitoring systems and dedicated software programs have been developed to monitor bogies, wheelsets, axle boxes, propulsion systems and rail tracks.

    An example is SKF’s IMx-R bogie condition monitoring system, which can be used to efficiently plan the bogie maintenance activities based on real component condition. The system includes sensors to detect running instability and bearing temperatures according to the requirements of the European Technical Specification for Interoperability, TSI Directive 96/48 EC. It provides a reliable performance overview that identifies potential damage before functional failure and the associated train service disruption, enabling operators to consolidate maintenance activities and perform necessary inspection and repair work during planned stops.

    All this can extend maintenance intervals by reducing downtime and improving reliability. The collected data also supports root cause failure analysis, which helps to eliminate recurring problems and failures through equipment improvements, redesign and upgrade.

    Service intervals can also be extended through approved lubrication techniques and by utilising automated lubrication systems. These can be fitted to critical equipment to dispense an exact amount of lubricant to bearings and other moving parts at predetermined intervals. It reduces the risk of under- and over-greasing and ensures consistent machinery performance. Determining the correct lubrication interval and quantity for the various bogie components was traditionally a matter of guesswork. These systems can also be linked to condition monitoring devices so that application of lubricants is based on actual operating conditions.

    Improved bearings
    Railway vehicle bearings must be dependable under extreme conditions. Wheelset bearings are among the most safety-critical components on rail vehicles, withstanding heavy loads with minimal maintenance and constant exposure to the elements, possible contamination and extremes of climate.

    Products such as compact tapered roller bearing units (CTBUs) are designed for use in all types of wheelsets, offering high load-carrying capacity in a small space. Low friction labyrinth seals ride on a special inner ring shoulder, which improves protection against contaminant ingress. The bearing also features a polyamide cage that minimises friction, roller slip and wear, while eliminating the risk of seizure. The CTBU can incorporate a sensor system to monitor wheelset conditions, such as: rotational speed for use in wheel slip/slide protection (WSP or WSSP), direction of movement for ATP systems as well as bearing temperature for the on-board monitoring system and traction control unit (TCU) systems. These Sensor signals are integrated on-board, for effective management of train movement and safety critical systems.

    Value added services
    Over the 30-year life of a train, services such as bearing refurbishment, bearing on site exchange and condition assessment can help to cut the time and cost of maintenance.

    Refurbishing bearings usually involves a thorough cleaning, with all parts visually and dimensionally inspected using purpose-made fixtures and measuring gauges. Customer bearings can be upgraded to allow the use of better greases and seals, amongst other component improvements to support reliability. OEM Refurbishment often exceeds the stringent Railway Industry standards for rolling bearings.

    On-site bearing replacement can cut costs, as it means an entire wheelset does not have to be replaced if a single component is defective. It involves the bearing supplier visiting the customer’s maintenance location with the equipment needed to exchange bearings on site. Typically, a complete bearing unit can be changed while the wheelset is still in the bogie at the depot under a train. Both bearings per wheelset can be changed in a few hours, so rolling stock can return to service as quickly as possible. Costs are a fraction of that for a complete replacement wheelset.

    To further extend maintenance intervals, experts can assess the condition of bearings and produce documented evidence of bearing condition, along with recommendations to achieve better value. When the condition of the bearings from a train are studied, and the grease is analysed, comparison with the application details can reveal ways to improve bearing performance – such as upgrading bearing seals during refurbishment.

    No component lasts forever, especially in the rail industry, but smart monitoring – and timely replacement – can ensure that any potential failures have a minimal effect on availability.

    Aktiebolaget SKF

    For further information, please contact:
    Press Relations: Nia Kihlström, +46 31-337 2897; +46 706 67 28 97;

    SKF is a leading global supplier of bearings, seals, mechatronics, lubrication systems, and services which include technical support, maintenance and reliability services, engineering consulting and training. SKF is represented in more than 130 countries and has around 17,000 distributor locations worldwide. Annual sales in 2015 were SEK 75 997 million and the number of employees was 46 635.

    ® SKF is a registered trademark of the SKF Group.

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