Arrangement for fastening a piston-cylinder arrangement and method for replacing sealings therein

A method of changing gaskets in at least one piston-cylinder arrangement (10,11) in a derrick (1) located on a drill floor (2), said at least one piston-cylinder arrangement (10,11) being adapted to raise and lower a yoke (8), which travels on guide rails (7) on the derrick (1), each of said at least one piston-cylinder arrangement (10, 11) comprising a cylinder (20), a piston (21) and a piston rod (22), wherein said piston rod (22) is joined at one end thereof to said piston (21), wherein said piston (21) is adapted to be inserted into said cylinder (20), an end of said piston rod (22) opposite said piston (21) being connected to the yoke (8), and said cylinder (20) being held securely with the aid of mounting apparatus (31) in relation to the drill floor (2), said method comprising the steps of:

• locking the yoke (8) to the derrick;
• relieving hydraulic pressure within said cylinder (20);
• exposing a locking device (38);
• removing a locking ring (34) from engagement with a flange (32) mounted on said cylinder (20);
• removing an end cover from said cylinder (20);
• lowering said cylinder (20) in relation to the drill floor (2) and said piston rod (22) such that said piston rod (22) is completely drawn out of said piston (21);
• removing at least one gasket (27) on said piston;
• replacing said at least one gasket (27) on said piston;
• raising said cylinder (20) such that said cylinder (20) is slid back onto piston (21) whereby said flange (32) is aligned with a fixing device (37);
• mounting the end cover on said cylinder (20);
• engaging the locking ring (34) between the flange (32) and the fixing device (37);
• securing the locking device (38) in place;
• restoring hydraulic pressure within said cylinder (20);
• and
• releasing the yoke (8) from the locked position on the derrick (2).