GB1023444A - Control system for a hydraulically operated engine - Google Patents

Abstract

1,023,444. Deep well pumps. KOBE Inc. Oct. 24, 1962, No. 40244/62. Heading F1A. The engine of an hydraulically actuated deep well pump is controlled by a reciprocating engine valve operated by a substantially constant valve operating pressure #p which is independent of the engine operating pressure differential. A bottom well housing 10 has a chamber 12 for an hydraulically operated engine and pump unit 14 and a chamber 16 for a separate engine valve means 18. The unit 14 is movable between its operating position in the chamber 12 and the surface through a tubing 20 and the unit 18 through the tubing 22, by hydraulic pressure. The unit 14 comprises a motor piston 38 and a pump piston 46 connected by a hollow rod 34 through which production fluid passes. The rod 34 has recesses 52, 50 which respectively interconnect passages 100, 102 and 106, 108 at the upper and lower ends of the stroke to cause actuation of the valve. The valve applies operating pressure Pi and exhaust pressure P 2 alternately to the end faces of the piston 38. The engine valve 78 has a differential area actuator 80 comprising a piston 98 reciprocable in a bore 84 the upper annular area of the piston being equal to the area of the upper end of the engine valve 78, which is constantly exposed to the supply pressure P 1 , and is constantly exposed to a valve operating pressure differential P 1 -#p. The operating pressure P 1 and the valve operating pressure differential P 1 -#p is alternately applied to the lower surface of the piston 98. When the groove 52 connects the passages 100, 102 the upper and lower surfaces of the piston 98 are interconnected by these passages, the passage 100 including a sharp edged orifice 104. The pressure P 1 -#p being applied to both surfaces of the piston 98 the valve 78 is moved down by the resultant pressure #p acting thereon. When the groove 52 connects the passages 106, 108 operating pressure P 1 passes to the passage 108 which when the piston 98 is in its lower position communicates by means of a groove 110, a sharp edged orifice 104 and a central bore 112 in the piston 98 with the lower surface of the piston so that the valve is moved upwardly by the resultant pressure #p. Further sharp edged orifices 114, 116 connect the central bore 112 with an annular clearance 118 the purpose of these orifices 104, 114, 116 being to control successive speeds of the engine valve 78. The pressure P 1 -#p is obtained by means of a valve 124 connected to pistons 128, 126 slidable in bores 122, 120 and loaded by a spring 138. The chamber 130 is connected to the upper surface of the piston 98 into which there is a constant leakage from the clearance 118 of operating pressure P 1 . Operating pressure Pi is also applied to the piston 126 which is opposed by the pressure acting in the chamber 130 and by the spring 138 which thereby controls the pressure in the chamber 130. To make this pressure independent of viscosity the annular area above the piston 126 is connected between an orifice 160, and a capilliary 162 in a passage connected between the pressures P 1 , P 2 . In a modification the pressure P 2 assisted by a spring is used to achieve a valve operating pressure differential i.e. P 2 + #p. In a further modification the restrictions 160, 162 are formed in the piston 126 and housing wall respectively. Governing means are provided for limiting the speed of the engine and pump plunger when the load thereon falls below a predetermined value and comprises a differential area pilot valve 174 the upper surface and annular surface of the valve being constantly subjected to pressure P 2 and P 1 respectively, these surfaces being of equal area. The lower surface is subjected to the pressure in the passage 188 which is alternately subjected to the pressures P 1 , P 2 by the valve 78. With the valves 78, 174 in the lower position, passages 192, 194 are connected by the valve 174 to apply the pressure P 1 -#p to the lower surface of the piston 98 and with the valves in the upper position the valve 174 connects the pressure Pi via the passages 186, 194 to the lower surface of the valve 98. The upper land 86 of the valve 78 is axially shorter than the lower land 78 hence ports controlled by the upper land 86 are fully open before those controlled by the lower land 88. V-shaped throttling grooves in the lower land 88 throttle flow under such conditions hence in co-operation with the pilot valve 174 the engine valve 78 is held in one or other of the throttling positions if the load on the engine and pump plunger 32 is below a predetermined value. In a modified pump construction the upper surface of the lower piston is an engine area together with the lower surface of the upper piston. The outer surfaces of the upper and lower pistons comprising pumping areas.