Swedish System for Safer Rail Joints and Critical Bolts
02 June 2005 16:04
NORD-LOCK washers are being used to improve safety by preventing vibration from loosening rail joints on London's Tube, says Metronet Rail, the company responsible for the renewal and upgrade of two-thirds of the Underground.
Metronet has tested the new washers on standard joints between Acton Town and Barons Court on the Piccadilly line (a Tube Lines route maintained by Metronet). Statistics prove that the new system works, improving safety on that route.
Tension is used to make the bolt self-locking. Two washers with interlocking, angled faces actually mean that the more the bolts and nuts are vibrated, the tighter is the force exerted by the washers to keep them in place. Bright yellow indicators also reassure track patrolmen quickly and clearly that nuts are tight.
NORD-LOCK, the firm which supplies the washers, tested track bolts for the company and proved that applying thread lubrication when tightening substantially increases the achieved bolt load. The washers do not impact the torque achieved, and are effective at both low torque (allowing short rail joints to “breathe” – expand and contract) and high torque (keeping tight joints secure).
Research is under way to ensure there are no negative effects of using NORD-LOCK on insulated block joint bolts used in the signalling system.
“It's a very good and simple system,” said track strategy manger Barry Reynolds, “and we are now going to roll out these washers across the sub-surface network to standard joints and ‘tight joints' (joints on a welded rail site).”
Pending overall results, Metronet plans to use these effective lock washers across its network as part of its constant focus to deliver a safe and reliable Tube.
For more information on this company:
NORD-LOCK - Wedge Effect Self-Locking Bolts for Rail Subassemblies
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