Hydraulic Bolting

Controlled bolting requires the use of a specific amount force to stretch studs putting them in tension while clamping to other surfaces together putting them in compression.  The applications for controlled bolting can vary from using mechanical torque wrenches to secure the nuts on wheels for Heavy Haul Trucks, to using Hydraulic Tensioners to install large heads on reactors.

The most important aspect in all applications is the accuracy of the of the applied load to the objects in tension.

Stretching Studs or Bolts can happen by 3 different methods:

This first method (Torqing) involves turning a nut onto the fastener.  In this instance the torque applied to the nut will stretch the stud putting it into tension.  Turning of the nut can be completed by a mechanical, hydraulic, Pneumatic or even battery powered tool.  The amount of tension on the stud is a function of the amount of force (torque) applied to the nut, the amount a friction that the nut encounters and the fastener material.

The second method (Hydraulic tensioning) uses hydraulic tensioners that directly pull on the fastener to stretch it a predetermined amount, and allows for the nuts to be set in place without much force on the nut.  Once the nut is secured into place the hydraulic tensioner is released, and the joint is set in compression.

The third method (Induction Bolting) uses heat, induced through magnetic fields, to expand the faster to a predetermined length.  Similar to hydraulic tensoining, the nuts can be set in place without much force.  Once the nut is secured into place, the fastener is allowed to begin the cooling, and the joint is set in compression.

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