Hydraulic pig advance system comprising a control volume chamber containing hydraulic fluid and a force transmitting member

摘要

This invention relates to a hydraulic pig advance system comprising a control volume chamber containing hydraulic fluid and a force transmitting member. The system further comprises two directional control valves which can be selectively repositioned to cause hydraulic fluid to cycle the force transmitting member back and force such that in each cycle, a metered amount of hydraulic is transmitted into a pig housing where it causes a pig to move a predetermined distance.