Bolt tensioner

In order to cope with the enormous axial forces in pressure generators or vessels, tie rods must be used. These are fastened to the flanges with nuts by using bolt tensioners. The Dunze GmbH supplies bolt tensioners since more than 40 years with great success.

The bolt is elongated by hydraulic pressure according to the operation pressure plus a safety value. There is no alternative method that works as precise as using bolt tensioners. Furthermore, they are a cost-effective way to handle larger screw joints.

The torque in the thread is about 80 to 90% smaller compared to the manual tightening and the setting forces are much smaller. Seizing of the thread has never been seen. Our bolt tensioners are made of high-strength aluminium and are lightweight.

As soon as pressure is built up, nut A pulls the tie rod to the left. Nut B can now be tightened by hand. As soon as the pressure is released again, the nut B absorbs the entire tension. Nut A and the bolt tensioning device can be disassembled again.

We developed and patented a bolt tensioner that is integrated in the flange. A separate device is no longer needed – simply apply pressure with a pump to assemble or disassemble the tie rod.

High pressure fluid

Our special hydraulic oil, that has a uniform viscosity even at very different pressures and temperatures, is prepared from carefully refined specialty base oils. By using shear-stable polymers, an extremely good viscosity-pressure behavior with a reliable viscosity is achieved.


Our nozzles, suitable for high-pressure technology, are made of high-strength stainless steels with natural or artificial diamonds added.
High-pressure nozzles are suitable for the sterilization, comminution and homogenization of fluids.

Threading Tool

Suitable cutting dies for cutting threads on high-pressure pipes and taps for the fittings are available from us. We also offer the required abrasives and lubricants.

Tube bending tool

High pressure pipes must not be bent by hand! It should be noted that the bending radius should be at least six times the diameter of the pipe.

To bend pipes, we offer special tools. For pipe sizes up to 9/16 “we recommend using our manual bending tool. All larger pipes should be bent with our hydraulic bending tool. Alternatively, angles can also be used.


Cone cutting tool

Frequent disassembly of the sealing cone and improper installation may result in wear of the inner-cone of the fitting. For reworking the cones, we offer the matching tool.
Our integrated patented spring package allows uniform cutting, even by less experienced people. The quality and construction of our cutting knives and sinkers promises cones with high surface quality.