The CMCE- (Crown Mounted Compensation and Equalization) cylinders are installed in the top of the derrick where they compensate vertical movements of the drilling rig relative to the ground fixed and standing still drilling rod.

Two main and two equalizing cylinders are always working parallel which requires identical friction behavior of each cylinder couple. Depending on the wave run the maximum moving speed of these cylinders can go up to 2 m/sec.

Because the cylinders have to realize this high speed movement with water based hydraulic fluid a special Hunger seal and bearing arrangement is considered in the design.

In case of the CMCE- main cylinders also some special features are integrated into the cylinder design. Their cylinder body is equipped with supports for an external guide rail where the middle beam of a pulley runs. And in the main cylinder itself the oil feeder for the above installed equalizing cylinder is integrated. The equalizing cylinders are designed as three chamber cylinders with a pretension piston which always guarantees a minimum tension in the connected tightrope.