Abstract: Apparatus and method for securing a cylinder liner to a pumping module. A first part of an assembly housing pistons is fastened to a pumping module and a second part of the assembly is brought against the first so that the pistons act on tensioning plates which each have a stud rod extending therefrom through the assembly at an end distal to the pumping module. Each rod has a first portion substantially surrounded in an elastomeric member and a second portion threaded to receive a nut. The rods are passed through a clamping ring on the cylinder liner and the nut is attached to the rod. Actuating the pistons causes initial compression of the elastomeric member by the tension plate and allows tightening of the nut toward the pumping module. Release of the pistons then causes expansion of the elastomeric member to urge the cylinder liner towards the pumping module.