Construction Fixings

In a positive development for bolted joint security in European steel construction, Nord-Lock Group and Peiner Umformtechnik are now collaborating to provide a maintenance-free, structural bolting assembly – consisting of an EN 14399-4/-8 spec Peiner HV bolt, together with a pair of Nord-Lock steel construction (SC) wedge-locking washers, which meet ETA requirements.

The fundamental idea behind bolting assemblies is to provide a solution whereby all components come from one manufacturer, who is responsible not only for the components themselves, but also for the friction coefficients, i.e. torque/preload ratios. Replacing commonly used flat washers with the more secure Nord-Lock SC washers, however, turns this basic idea on its head, and is permitted through approvals issued on both a national basis in Germany, via the Deutches Institut für Bautechnik (DIBt, Z-14.4-629), and on a European basis via the European Organisation for Technical Assessment (ETA – 20/0010). However, friction coefficients and required torques differ between the two, details of which can be found in the respective approval documentation. 

As Europe’s largest HV bolt manufacturer, Peiner Umformtechnik supplies more than 20 million structural bolting assemblies each year and is now the first manufacturer to offer the entire bolting assembly from a single source. This new offering underpins the basic idea that structural bolting assemblies should come from one supplier. The company has conducted many internal tests and is in favour of improving its assemblies with Nord-Lock SC washers, the addition of which increases the security of bolted connections. 

While regular HV assemblies with plain washers are common to the steel construction industry, and have proven themselves over time, they only have limited integrity when exposed to dynamic loads. Bridges, crane tracks, storage racks, conveyor systems, and all manner of warehouse infrastructure, or steel constructions, are exposed to extreme vibrations, dynamic loads or thermal movements. With this new development, however, Peiner HV bolting assemblies, used in conjunction with Nord-Lock SC wedge-locking washers, will help prevent loosening under these conditions, maintaining high preload and secure bolted joints.

Frank Götz, Nord-Lock’s senior steel construction expert, comments: “While in some places it’s already standard practice to replace flat washers with Nord-Lock SC washers, in other countries there are still major reservations. The main points of discussion are the standards EN 1090-2, EN 14399 and the associated CE Marking.” 

Accordingly, Nord-Lock SC washers are only to be used with components that have a CE Marked structural bolting assembly, which effectively results in a new assembly meeting Z-14.4-629 or ETA specifications.

Junker test results

At Nord-Lock’s R&D laboratory in Mattmar, Sweden, plain washers (EN 14399-6) were compared with Nord-Lock SC washers (ETA – 20/0010) in Junker testing to measure the locking security when used with M30 Peiner HV bolts. The results of this Junker test – the world’s most severe vibration test to determine the point at which fastener securing elements fail when subjected to vibration, and based on DIN 65151 – prove the Nord-Lock difference. 

With plain washers, tension drops dramatically within a few seconds of running the test and preload falls completely to 0kN in just over 60 seconds. With Nord-Lock SC washers, however, after a small loss in preload, due to initial settlements, a strong and stable clamp force remains in the bolted joint throughout the testing – proving that even under demanding conditions Nord-Lock SC washers are prevented from spontaneous loosening – thanks to the wedge geometry created when using the two solutions as a pair.

Renè Tomasch, Peiner’s manager sales engineering, stated that by meeting the specific demands of the market and its customers, Peiner has been able to offer the “best solution for every requirement” using these high strength, maintenance-free bolt assemblies, together.