Engineering solutions provider Bearing Man Group has extended its range of Nord-Lock bolt-securing systems to include Nord-Lock’s X-series washers, which are designed to safely secure bolted joints exposed to severe vibration and dynamic loads.
“Bolted joints normally fail owing to spontaneous bolt loosening and slackening,” says BMG’s fasteners, tools and equipment division manager, Darryl Campbell.
“Bolted joints in heavy industries are constantly subjected to external forces, such as vibration and dynamic loads, which result in spontaneous loosening. With the development of new materials and techniques – such as corrosion-resistant composites – slackening is a common problem that results from settlement and relaxation,” he adds.
Campbell highlights that Nord-Lock’s X-series washers are designed for increased bolt security, even in the most demanding operating conditions. The wedge-effect design prevents spontaneous bolt loosening and an integrated spring effect of the system compensates for the loss of preload owing to slackening.
Each washer pair has cams on one side and radial teeth on the opposite side to secure the bolted joint with tension, rather than friction, Campbell explains. The conical shape of these washers creates an elastic reserve in the bolted joint to compensate for the loss of preload, thereby preventing slackening.
He points out that advances in polymers and sandwich composites technology have the advantage of strength-to-weight ratios and corrosion-resistant properties that make applications lighter without losing strength. However, these materials are softer than metal materials previously used and make slackening an additional challenge. The multifunctional wedge-locking concept of the X-series combats these problems.
“Surface treatments, which are common for corrosion protection, can also cause slackening as the bolt sinks into the treated surface after tightening. “Even a thin surface of 1 mm would normally put bolts at risk, but with the compensating spring of the X-series washers, slackening is prevented,” says Campbell.
The combined tension and spring action of the X-series washers combats the effects of surface treatments, thermal cycling and vibration.
It is quick and easy to install and remove the washers using standard tools and they have been certified by international institute for quality and safety certification TÜV.
“All bolted joints have a functional preload range in which the joint is safe. Serious problems start as soon as the preload falls outside the functional range. If the preload is too high, yielding occurs. If it is too low, there is separation or sliding between the parts,” notes Campbell.
He adds that independent tests show this series performs better than conventional washers when compensating for slackening in static conditions and to prevent rotation of the fastener when the joint is exposed to vibration in the dynamic phase. “These are the only washers currently available that can secure bolts from both critical loosening factors – spontaneous loosening and slackening – at once.”
Nord Lock History
The Nord-Lock group states on its website that it has been dedicated to safe bolting since 1982. The company’s expanding sales organisation has subsidiaries located in Europe, the US and Asia. Nord-Lock, which is wholly owned by Stockholm Stock Exchange-listed Investment AB Latour, also has a worldwide distribution network through sales partners and author- ised distributors.
In 2011, the Nord-Lock group acquired Superbolt and P&S Vorspannsysteme, now known as Nord-Lock.