Screw the Hydraulic Nut (HM) on the bolt to be pretensioned,
and down to the flanges' surface. A hydraulic high-pressure
generator pumps the oil through a high-pressure hose into the
space between cylinder and piston. The hydraulic pressure rises.
Through the rising pressure and the resulting axial force,
the bolt is elongated and the flange parts are compressed.
The lock nut is lifted off the cylinder. When the preset
pre-tensioning force is achieved, the pressure supply is stopped.
Screwing the lock nut
The pre-tensioning force has been achieved and the lock nut is
turned by hand down to the stop face of the cylinder.
Thus, the pre-tensioning force is maintained within the
screw joint and the hydraulic may be released.
The Hydraulic Nut remains on the bolt connection.