Business profile
when the supporting documentation and certification is often as important as the physical solution itself. While the investment in getting to the
root cause of a problem may seem higher than simply sending equipment away for routine repair, the rewards come in the form of a more reliable fleet, and an overall reduction in whole life and indirect costs. There is no doubt that original
equipment manufacturers want to offer support for their equipment, and may want to make engineering changes to solve problems if it is in their interests to do so. What is missing is the unbiased, open and honest approach to customer relations, and the willingness to work directly with the maintenance engineers on site if necessary, regardless of the scale of the problem. SET’s maintenance solutions extend
beyond simple repair, aiming to get to the root cause of all repeat failures and intermittent problems, taking the burden away from the maintenance personnel who may otherwise be frustrated by having to continually swap out the same items for the same repeating faults.
Does it really work? The company has recently introduced a new website with a number of brief case studies based on previous maintenance solutions. The example below is based on work undertaken for one of its major UK rail customers. SET was asked in 2009 to assess a
traction inverter and related equipment from a modern passenger DEMU with a view to repairing this equipment on an ongoing basis. A detailed repair history is
kept by SET for traceability purposes and this is the point at which fault patterns and repeat failures are detected. SET was informed from the outset
that the equipment had a mysterious fault that resulted in repeated reports during operation in service, which was not evident during standard repair tests – resulting in equipment yo-yoing between the vehicle and the repair facility – with obvious cost and reliability implications. As this was an ongoing problem with the previous repairers, SET was determined to find the root cause of the problem and discovered that ageing effects were producing intermittent connectivity within a sealed component, leading to erroneous errors being reported. As a result, a highly sensitive test method was developed that was capable of detecting the failure at an early stage. Since this test was introduced, the mysterious cases of no-fault-found have ceased to be an issue. The investigation indicated that the
particular component involved had been designated as obsolescent, so over a period of several months, SET performed a thorough investigation into a suitable replacement for the component, which included: • thermal modelling and life-cycle prediction of the original and alternative components
• collaboration with the semiconductor manufacturers to confirm the above predictions
• transient thermal testing using an in- house test rig
• transient electrical testing to analyse the behaviour of the component in its
application
• whole train EMC testing supported by York EMC.
• independent verification of a section of our work by Lloyds Register Rail.
A further result of this in-depth testing
was that an intermittent fault on the gate driver PCB was narrowed down to thermal cycling on a surface-mounted component introducing microscopic cracks in the solder connections, causing sporadic destruction of the main power control devices (IGBTs). SET devised a suitable solution which has been in place for several months with no repeat failures and a significant reduction in the direct and indirect costs of failure.
Support for obsolete equipment As the expected lifetime of rolling stock is long compared with the rate at which electrical and electronic technology progresses, it is common to find obsolete technologies still in use on current rolling stock, such as the use of thyristors instead of modern power semiconductors, and the use of magnetic amplifiers in place of conventional power regulators. In the process of supporting
maintenance and spares departments, obsolescence is an area in which SET’s experience has allowed it to provide engineering solutions in the form of new-build replacement sub-assemblies to replace those which can no longer be economically repaired. Visit
www.set.gb.com To discuss your problem (technical calls welcome) call 01332-346035 or email
sales@set.gb.com
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