Abstract: This invention effects a significant reduction in leakage along a piston reciprocating in a cylinder and having a high fluid pressure differential existing between one end of the piston and the other. A large number of closely spaced, annular grooves are provided on the periphery of the piston and the clearance between the non-grooved piston diameter and the interior wall of the cylinder is maintained at a value significantly larger than that commonly employed between a smooth cylindrical shaft and a cylindrical interior sealing surface. The employment of such unexpectedly large clearance not only provides reduced fluid leakage for lighter density fluids when the equipment is relatively new, but the leakage becomes substantially less than that encountered in a smooth surface bearing construction as the piston and cylinder surfaces wear and increase the clearance.

Abstract: The invention relates to a cleaning unit for power driven pumps which are required to pump fluids containing significant quantities of particulate material of greater spcific gravity than the fluid. A portion of the pressured fluid output of the pump is utilized to drive a fluid motor which in turn rotatably drives a centrifugal separator. The separator has its inlet connected to the source of particulate containing fluid and effects the centrifugal separation of such fluid into two streams, respectively a clean fluid stream and a particulate containing stream. Means are provided for discharging the particulate containing stream and a diffuser means is provided for converting the rotational energy in the clean fluid stream into a pressure head which is employed to transfer the clean fluid to the inlet of the pump.

Abstract: The invention provides a high flow rate standing valve for oil wells of the type employing a plurality of check valve units disposed in parallel between inlet and outlet passages, the flow area of the inlet or outlet passage each being not in excess of the total flow areas of the individual check valves so that no significant pressure drop is produced by fluid flow through the check valves in their open position. Specifically, the invention provides an improved configuration for such standing valves permitting the convenient manufacture and assembly of the valve components. In a modification of the invention, the standing valve housing is constructed so that its lower end is mounted on and co-operates with a conventional well safety valve.