Passive operation of the existing DSC utilizes the existing controls and is identical to that prior to the addition of the MICAS equipment. while the active compensation controls are used to select passive mode, once passive operation is selected the DSC is operated using the existing DSC control console in the identical manner as before. During passive operation, the pump module is bypassed and no DSC cylinder fluid is passed through it. Since the pump module is not required, the active compensation HPU may also be shut down.

Active Operation

The active compensation system function is based on the principle that a 100% efficient DSC and an infinite APV volume would perfectly compensate for vessel heave about the bore hole or water column reference point. As neither of these conditions are achievable, the active compensation system operates in a manner to aid the DSC motion such that the effects of motion inefficiency and limited A.V. size are neutralized, resulting in DSC operation that more closely approaches ideal motion compensation.

The DSC must be operating in passive operation with the hook load compensated by proper adjustment of the APV air pressure prior to selecting active mode operation. This is required as the APV air pressure compensates essentially the entire hook load with the ACM providing the additional 10 percent to add or subtract to compensate for various operating losses. This additional + 10 % of load is used to offset the APV pressure, affecting the resultant hook load such that the load motion is in the proper direction to compensate for detected motion errors, effectively counteracting the effects of system inefficiency and gas compression losses.

Proprietary Information of Control Flow Inc.