Tensioning

Bolt tensioning is method of tightening and loosening bolted connections using hydraulic power. In order to work, a high-pressure hydraulic pump is connected to the bolt tensioning tool using a semi-flexible hose. The tensioner then generates a large axial force proportional to the input pressure which stretches the stud and the nut is tightened down against the flange and the hydraulic pressure is released. The bolt and nut now retain the desired clamping load.  

Bolt tensioning reduces the number of uncertainties when compared with traditional torque methods. If bolt geometry and joint stiffness are known, the load transferred during tensioning is calculable. Bolt tensioning with stretch control technique can result in a preload scatter at low as +/-5%, compared to torque control methods that can yield preload variances up to +/-30%.

Galling is a form of adhesive wear which occurs when two surfaces are under high contact pressure with relative motion. When tightening a nut using traditional torque methods, the thread flanks see increasing contact pressures as bolt preload increases. When severe, galling can result in a threaded connection that is cold-welded together and cannot be removed.  High temperature or highly ductile bolting materials (Aluminum, Stainless Steels, Inconel, Titanium) are even more prone to this situation.

In highly loaded fasteners, traditional torque methods can cause the stud to windup (twist) as the contact pressures and frictional resistance increases at the thread interface. During service these loads can relax causing the joint to loosen over time. Tensioning applies a purely axial force to stretch the bolt.  Since the nut is turned down independent of the applied load friction is significantly reduced eliminating torsional wind up of the stud. 

Multiple tensioners can be linked together and powered by a single pump kit. Elastic interactions between adjacent bolts are greatly reduced, thus resulting in higher pre-load accuracy and reduced installation times. 

A  selection of manual and air driven pump kits designed for any hydraulic application requiring pressures up to 40,000 psi. For use as an accessory for our tensioning and coupling installation product lines.