Taking away the tension of large bolted joints

Written by: Heico Fasteners UK Ltd | Published:

Large bolted joints are all around us in safety critical applications from power generation to heavy industry, construction to offshore. Ensuring the correct tensioning of these large bolted joints is a complicated but critical process but HEICO are now making it simpler, faster and more reliable.

When tensioning bolted connections the turning movement results in axial elongation and preload of the bolt due to the inclined plane of the bolt threads. This leads to thread deformation, reducing the pre-load, durability and re-usability of the bolt.The torsion stress from thread friction and deformation also reduces the axial load bearing capacity of the bolt.

Tensioning of large bolted joints usually requires the use of specialist tools, adding additional costs to your project.Here the bolt is elongated and the nut is then tightened free of load. The pressure is released and the bolt contracts, resulting in the proper tension in the bolt being achieved.The disadvantage of this process is that as the nut was not pre-tensioned while the bolt was elongated, a percentage of the elongation of the bolt is lost in joint settlement meaning only around two thirds of the bolt strength can be utilized. The unique design of the new HEICO-TEC® tension nut eliminates the requirement for specialist tools, saving both time and money, whilst also improving performance.

With HEICO-TEC® several small thrust bolts with associated pressure pins are arranged around the main thread inside the nut body.When the thrust bolts are tightened they push the pressure pins against the clamped parts while simultaneously elongating the bolt.The smaller trust bolts mean a conventional torque wrench is all that is needed to achieve the required axial pretension force, so considerably reducing thread friction and deformation and ensuring full utilization of the load bearing capacity of the bolt.

As HEICO-TEC® complies with DIN EN ISO 898-2 it can easily be used as a direct replacement for any hex nut from the same strength class. Its’ unique design makes it highly resistant to loosening forces and is also totally reusable with its greater flexibility reducing the bolted joint’s dynamic stress and increasing its service life.

w: www.heico-tec.com

e: sales@heico-fasteners.co.uk

t: 01268 745421


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