Maximum Stroke Indicator
A red line machined into the circumference of the piston indicates the tensioner maximum allowable stroke.

Continually monitor the piston stroke during the tensioner pressurisation.
If the maximum piston stroke indicator becomes visible on any of the tensioners before the target pressure is reached immediately stop the pump, tighten the nuts down and then release the pressure to zero.
Rotate the thread inserts until the pistons are shut down into the zero stroke position.
Recommence the tensioning procedure.