Power Transmission
(Overhead Lines)

KJ Fasteners are an approved supplier to all major fabricators servicing the Over Head Power Line market. 

The whole range of fastener assemblies for power transmission towers, including those for National Grid and Scottish Power towers, are stocked. These include structural assemblies with bolts threaded 1D + 10mm and 1½ D, non-structural stepbolts and structural stepbolts to various drawings. Inch (BSW) fastener assemblies are stocked in large quantities to enable the refurbishment of existing power lines.

All metric structural fastener assemblies can be supplied with certification and CE marking in accordance with BS EN 15048-1.

The bolts which have short thread lengths are specified in lengths that ensure that the full diameter shank is both in the shear plain and the full length of the connection. This ensures the maximum strength in a shear and bearing connection, especially with the close tolerance fasteners and clearance holes required for National Grid towers.

Long term protection for fasteners in the power transmission towers is measured in terms of a working life in decades rather than months or years.

Therefore the choice of a protective coating is of major importance to the structural engineer.

Traditionally and currently that protective coating has been hot dip galvanizing, the current standard is BS EN ISO 10684, with a local minimum coating thickness of 40µm and a batch thickness of 50µm; the actual thickness is usually 65-70µm. Galvanizing produces a tough metallurgically bonded zinc iron alloy that is resistant to mechanical damage and is 10 to 15 times thicker than most electroplated zinc. To accommodate the thickness of zinc on the thread nuts are tapped oversize to tolerance class 6AZ; to meet the tensile resistance requirements of BS EN 15048-1 the next higher grade of nut is supplied with the assemblies.