CMCs

Definition: 
Crown Mounted Compensators
Subject Area 1: 
Drilling & Operations
Remarks: 
The purpose of the NOV Crown Mounted Compensators is to apply a constant tension to the drill string and compensate for any rig movement. Correct weight on bit (tension in drill string) is extremely important to maintain efficient drilling and long drill bit life. The CMC is installed on top of the derrick. They all comprises of a pair of vertically mounted hydraulic cylinders whose function is to convert load to hydraulic pressure. The piston rods are attached directly to the crown block.