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Top Collar Hydraulic Nut

Supplier: National Tools And Hose

Tentec Nuts replace existing hexagon nuts to give a rapid, accurate and uniform Bolt load to any bolted joint.


The Tentec Nut offers a method of bolt tensioning multi-bolt applications which greatly improves the integrity of the joint.

The speed in which joints can be tensioned and detensioned shows an extraordinary time saving over conventional detachable bolt tensioning systems.

An existing Oil company user of Tentec Nuts has recently reported a massive time saving of 1750% over there old bolt tensioning system

The Principle

Hydraulic pressure is applied simultaneously to each Tentec Nut.

All frictional factors connected with conventional bolt tightening methods are alleviated since Tentec Nuts apply a direct axial force to the bolt which generates a bolt elongation.

This elongation/tension is permanently retained by means of the Load retaining Collar. Tentec Nuts have been designed to be as compact as possible, in order to allow adjacent fitment on as many applications as possible.

In most cases they are designed to produce a residual bolt stress of 45000 lbs/In2 (310N/mm2) which is more than adequate for most bolted joint applications.

As pressure is applied to the Tentec Nuts not only does the bolt elongate but also joint compression occurs.

Since many applications incorporate some form of gasket, this joint compression can be substantial, in order to withstand this joint compression all Tentec Nuts are capable of considerable piston movement.

This allows the tentec Nuts, in most cases, the ability to tension a complete joint in only one pressurisation sequence, this can result in extremely high time savings.


  • Standard Tentec Hydraulic Nuts are suitable for use in temperatures up to 100Âșc. For temperatures above this level special seals are available, contact Tentec for further details
  • The use of machine cut Polyurethene seal, ensure a reliable leak free Tensioning system
  • Tentec Nut protection caps are available to protect against corrosion
  • Tentec Nuts can be used with Spherical washers where joint members are badly out of square