VARIABLE SPEED PIPELINE PIG WITH INTERNAL FLOW CAVITY

摘要

A pipeline pig includes a plurality of relief channels and a bypass channel extending therethrough. To regulate a speed of the pipeline pig, relief valves within the relief channels open when a differential pressure between upstream and downstream ends of the pipeline pig reaches a pre-selected minimum relief pressure. If the differential pressure reaches a pre-selected maximum relief pressure, such as when the pipeline pig encounters an obstruction, the relief valves close to allow the differential pressure to further increase to clear the obstruction. If the further increase in differential pressure is insufficient to clear the obstruction and the differential pressure reaches a pre-selected minimum bypass pressure, a bypass valve opens to permit fluid flow through the bypass channel while the relief valves are closed. Flow through the bypass channel operates to reduce turbulence and permit production through the pipeline if the pipeline pig becomes stuck and obstructs the pipeline.

主权项

1. A pipeline pig, comprising:
a housing defining a trailing end, a leading end and longitudinal axis extending therebetween; a bypass channel extending longitudinally through the housing between the trailing end and the leading end thereof; a bypass valve disposed within the bypass channel, wherein the bypass valve is operable to maintain a restrictive configuration in which a pipeline fluid is prohibited from flowing through the bypass channel when a differential pressure established in the pipeline fluid between the trailing end and the leading end of the housing is below a pre-selected minimum bypass pressure, and wherein the bypass valve is operable to move to a bypass configuration in which the pipeline fluid is permitted to flow through the bypass channel in response to the differential pressure reaching the pre-selected minimum bypass pressure; at least one relief channel extending longitudinally through the housing between the trailing end and the leading end thereof; and at least one relief valve disposed within the at least one relief channel, the at least one relief valve operable to move from a first closed configuration to an open configuration in response to the differential pressure reaching a pre-selected minimum relief pressure and operable to move from the open configuration to a second closed configuration in response to the differential pressure reaching a pre-selected maximum relief pressure, wherein the at least one relief valve prohibits flow of the pipeline fluid through the at least one relief channel when in the first and second closed configurations and permits flow of the pipeline fluid through the at least one relief channel when in the open configuration, and wherein the pre-selected minimum bypass pressure is greater than the pre-selected maximum relief pressure, and the pre-selected maximum relief pressure is greater than the pre-selected minimum relief pressure.