Fluid propelled pipeline pig with controlled fluid by-pass

摘要

The pig (10) comprises a body (14), at least one flexible annular outwardly extending seal (16,18) sealingly contracting a pipeline interior wall under differential fluid pressure whereby to propel the pig along the pipeline (12), fluid bypass duct means (20) through the body and resilient frictional means (22,23) on and extending from the body adapted to contact the pipeline interior wall and exert a drag on the pig. An adjustable bypass flow control sleeve valve (24) is provided to regulate fluid flow through the duct means and thus the speed of the pig, the valve being operated by a microprocessor controlled hydraulic actuator 30 extending to open, or close outlet vents 28.