Hydraulic Bolt Tensioners

A hydraulic bolt tensioner is a high pressure hydraulic load cell that stretches the bolt before a techniican manually turns the nut which allows safe, effective and even clamp load when tightening.

Torque and Tension are two different methods that are trying to accomplish the same end goal – proper clamp load. Torque uses force to turn the nut which in-turn causes the stretch of the bolt to increase. After turning the nut to a set value, this should meet the engineering spec to achieve proper clamp load/force on your fastener. A bolt tensioner stretches the bolt first as opposed to turning/torquing the nut. Once the proper load has been achieved from the bolt tensioner, the nuts are turned hand tight. After all nuts have been secured, the pressure from the hydraulic tensioner is released back into the pump.

You first start by assesmbling a bolt tensioner to a bolt/stud. Once all components are connected you will connect your hose to the pump, you will proceed by building pressure and bringing your tensioner or tensioners to your first pressure rating. Once the bolt/nut have been lifted, you will turn the nut until you see no more gap between the nut and the surface of the application. Once the hydraulic pressure is released, the nut traps the remainder of the stretch in the bolt. This is when load is achieved.

A bolt tesnioner uses a hydraulic load cell that surrounds the nut & bolt. Part of the tensioner uses a threaded puller to attach to the bolt. When the hydraulic cell is charged, the counter force due to the puller being threaded on to the bolt will cause the bolt to be stretched. While the bolt is stretched, you will manaully tighten the socket ring to hand tightern the nut then release the pressure. At this point clamp load has been achieved.