Hydraulic Bolt Tensioning

A hydraulic bolt tensioner is a "system" consisting of a puller which threads onto the end of the bolt, a socket which fits over the nut and, an annular jack positioned between the two.  As hydraulic pressure is applied,  the jack pushes against the joint flange and the puller stretches the bolt. Because the force produced by the jack is applied directly to the end of the bolt, a tension equal to the load generated by the jack is developed in the bolt's shank.  With the jack applying the tension, it's possible to turn the nut with zero torque until it is tight. After hand-turning the nut as far as it will go, the hydraulic pressure is released and a calculated  percentage of the load is retained in the shank of the bolt.

Flexible hoses with self sealing quick connect couplings are used to gang a number of bolt tensioning tools together to form a hydraulic ring main.  The ring main and tensioning tools are normally pressurised using an air driven pump working from a compressed air supply.

Bolt Tensioning

...how it works