Abstract: A strainer system having two separate strainers positioned in parallel, where one strainer can be cleaned while still permitting normal flow through the other strainer. The system flow circuit is arranged so that a high pressure backwashing flow can be applied to one strainer while the other strainer is providing its normal straining function. The backwashed strainer is then isolated by valves so that its access flange can be removed and the particulate buildup within the valve plug cleaned out. The strainer is then returned to service following the replacement of the access flange. In this manner, it is possible to alternate between the two strainers so that continuous flow can be maintained to the hydraulic choke located downstream of the strainer system.

Abstract: The invention contemplates a strainer based upon a four-way, two-position rotary cylindrical plug valve having a hollow plug. The normal entry port for the sealing plug of the plug valve is a circular radial hole passing from the exterior of the plug into the interior cavity of the plug. The normal exit port for the sealing plug is a regular array of small holes across from and coaxial with the normal entry hole. The ports for the valve body are in two pairs positioned at 90° from each other, with the axes of the ports lying in the same transverse plane as the ports of the valve plug.

Abstract: An embodiment of the invention involves a method for servicing a choke valve that includes disconnecting a choke actuator and at least one internal valve component engaged therewith from the choke valve body of the choke valve and moving the same in a generally linear path away from the choke valve body along the axis of the choke valve body.

Abstract: A valve comprising a housing with an inlet and outlet and a chamber in between, a reciprocating gate mounted in a gate seat disposed within the chamber for opening and closing the valve, an upper bonnet for closing the chamber at one end and a lower bonnet for closing the chamber at the other end, the gate being disposed between upper and lower stems which extend into the upper and lower bonnets respectively. Metal-to-metal seals are provided at all junctures between the above members in the lower gate position with back-up seals at the junctures of all moving members.A double edged seal ring integral with the upper stem self-contained within the upper bonnet provides a metal-to-metal seal with the upper bonnet in the upper and lower gate positions of the valve.A metal gasket arrangement is provided between the upper bonnet and valve body whereby the assemblage of all points of contact between the gasket and body form an annular ring.