Abstract: Pigs (10) are propelled forwards by a propulsion fluid in a pipeline (21). The pigs (10) have an upstream end (13), a downstream end (11), and an intermediate section (12). The intermediate section has a variable geometry chamber (16) associated therewith and one or more outwardly extending external pawl teeth (15). The pawl teeth are automatically displaceable outwardly relative to a longitudinal axis (9) in response to a pressure differential between a downstream pressure and an upstream pressure. The pig is configured such that a change in a geometry of the chamber in response to the pressure differential between the downstream pressure and the upstream pressure causes the one or more pawl teeth to automatically displace outwardly when the upstream pressure is less than the downstream pressure. When the pawl teeth are deployed, upstream displacement of the pig is inhibited. Various related systems (5) and methods are also disclosed.

Abstract: Pigs (10) are propelled forwards by a propulsion fluid in a pipeline (21). The pigs (10) have an upstream end (13), a downstream end (11), and an intermediate section (12). The intermediate section has a variable geometry chamber (16) associated therewith and one or more outwardly extending external pawl teeth (15). The pawl teeth are automatically displaceable outwardly relative to a longitudinal axis (9) in response to a pressure differential between a downstream pressure and an upstream pressure. The pig is configured such that a change in a geometry of the chamber in response to the pressure differential between the downstream pressure and the upstream pressure causes the one or more pawl teeth to automatically displace outwardly when the upstream pressure is less than the downstream pressure. When the pawl teeth are deployed, upstream displacement of the pig is inhibited. Various related systems (5) and methods are also disclosed.

Abstract: A check valve is provided comprising a conduit for conveying a fluid, the conduit having an inlet and an outlet, the conduit having a first region adjacent the outlet (13) comprising a flexible wall, two opposing sides of the flexible wall converging towards each other to form a closed geometry when the pressure of the fluid upstream of the inlet and the pressure of the fluid downstream of the outlet are substantially equal, the closed geometry comprising each of the opposing sides (23, 24) being arcuate in cross-section and lying against each other in a substantially sealing relationship (21, 22). Preferably, two connecting regions of the wall connecting the two opposing sides (15, 16) are biased towards each other by a biasing means. Preferably, the biasing means comprises one or more flexible ring members (25) encircling the flexible wall attached at points (25A and 25B). Preferably, the conduit takes the form of a duck beak valve (20). The figure shows an end view onto the check valve outlet.

Abstract: A check valve is provided comprising a conduit for conveying a fluid, the conduit having an inlet and an outlet, the conduit having a first region adjacent the outlet (13) comprising a flexible wall, two opposing sides of the flexible wall converging towards each other to form a closed geometry when the pressure of the fluid upstream of the inlet and the pressure of the fluid downstream of the outlet are substantially equal, the closed geometry comprising each of the opposing sides (23, 24) being arcuate in cross-section and lying against each other in a substantially sealing relationship (21, 22). Preferably, two connecting regions of the wall connecting the two opposing sides (15, 16) are biased towards each other by a biasing means. Preferably, the biasing means comprises one or more flexible ring members (25) encircling the flexible wall attached at points (25A and 25B). Preferably, the conduit takes the form of a duck beak valve (20). The figure shows an end view onto the check valve outlet.