Automatic pressure control valve

摘要

922,227. Fluid-pressure servomotor control systems; valves. THORNHILL-CRAVER CO. Inc. July 6, 1959 [May 18, 1959], 23156/59. Class 135. A valve suitable for use in petroleum well-head equipment and arranged to close in the vent of excessive downstream pressure or in the event of excessive drop of pressure on the downstream side due, e.g. to pipe breakage comprises a main valve member 15 coacting with a seat 14 and actuated by a differential piston 24, a chamber 26 at the larger end of which connects through a restriction 33 and pipe 32 with the downstream side of a restriction 11 downstream of the valve, and a chamber 25 at the opposite, smaller end of the piston connects through a passage 29 and a bore 31 in the valve stem with the high pressure side of the valve. If, while the valve is open, the downstream pressure drops unduly the reduction of pressure in the chamber 26 allows the valve to close, and during closure a reduced part 79 of the valve stem moves into line with a vent 78 whereby the pressure in the chamber 26 is reduced quickly. A pilot valve 17 for controlling opening and closing of the main valve is connected through a chamber 48, Fig. 2, and check valve 60 with the chamber 25 and through a pipe 38 with the chamber 26. When the movable member of the pilot valve, which is held against rotation by a projection 58 engaging a slot 59, is moved to the left by a nut 56 driven by a hand wheel 57 having a locking screw 62 it opens the check valve 60 and connects the chamber 25 with the pipe 38 and chamber 26 so that high pressure in the latter opens the main valve. The pilot valve member may then be set in the position shown in which the check valve 60 is closed and the pipe 38 is connected through a passage 51 with pressure relief means, 39, e.g. a frangible disc, so that an excessive rise of pressure downstream of the main valve and acting in the chamber 26 will be released from the latter to allow the main valve to close. The main valve may also be closed by operation of the pilot valve member to the right so that it vents the pipe 38 through an opening 52. The position of the pilot valve member is indicated by means 61. Alternatively, the hand wheel may be geared to an electric motor for remote control and the pilot valve position indicated by lamps.