GB1171550A - Free Plunger Pneumatic Arrestor and Control System for Well Pumping Apparatus - Google Patents

Abstract

1,171,550. Hydraulic reciprocating pumps. E.K. MOORE. Oct.27, 1967, No.48866/67. Heading F1A. A well pumping apparatus, e.g. for oil-gas mixture, comprises a free piston 200 in the well tubing string 20 which is moved upwardly by the well pressure beneath it to lift a slug of oil up the tubing when an outlet valve 38 is opened to release the pressure above the piston, the slug being discharged through a pipe 32 and the plunger averted at the top of its stroke by a pneumatic shock absorber, which acts to close valve 38 for the downward stroke of piston 200 under gravity. Valve 38 is operated cyclically by a timing device 40, 41 incorporating a multi-lobed cam wheel controlling the flapper valve of a pneumatic pilot valve which supplies pneumatic pulses to the actuating diaphragm of valve 38, Figs. 4 and 6 (not shown). The device 40, 41 operates at a rate determined by the well characteristics, the pneumatic shock absorber additionally acting to close valve 38 when the piston reaches the top of its stroke. The shock absorber comprises a piston 50 which is engaged by the piston 200 and moved upwardly to pressurize gas in chamber 35 the gas pressure acting through a needle valve 70 to operate a piston to trigger the closing of valve 38, Fig. 3 (not shown). A spring 66 on piston 50 provides additional shock absorption. A check valve 62 in piston 50 permits its downward stroke. The free piston 200 has a segmental seal 202 which is expanded to seal against the well tubing when the piston strikes the bottom of the tubing, and is retracted, to permit the downward stroke under gravity, when the piston strikes the pneumatic shock absorber piston. The seal comprises segments 204 mounted on a piston portion 210 which is axially movable relative to piston portions 206, 220. The segments 204 are loaded by springs 248 outwardly from the piston and have tapered surfaces 280, 260 co-operating with corresponding tapered surfaces on piston portion 206 and a collar 205, so that relative axial movement between the piston portions causes outward or inward movement of the segments. A spring-loaded ball 256 engages in grooves 252, 254 to hold the segments in their extreme positions.