GB953164A - Control arrangement for use with hydraulic ram and selector mechanism - Google Patents

Abstract

953,164. Fluid-pressure servomotor control systems. TURNER MANUFACTURING CO. Ltd. April 12, 1960 [April 14, 1959], No. 12633/59. Heading G3P. A control arrangement for use with hydraulic ram 37 and selector mechanism of the type disclosed in Specification 860,665, for controlling a valve, such as a butterfly valve 1, comprises an hydraulic pilot circuit P having separate branches for causing movement of the ram selector 23 in opposite directions, valves 15, 16, 17 in the pilot circuit operated, by remote control from means responsive to changes in operating conditions of the valve controlled by the ram and a pair of plungers 28, 29 which are, alternatively, hydraulically locked or displaceable relative to one another and adapted to co-operate to control fluid flow in at least one branch of the pilot circuit. The valves 15, 16 are actuated via diaphragms 11, 7 which are controlled by pressure-sensitive pitot tubes 5, 6 and flow-sensitive pitot tubes 3, 4 respectively, and the valve 17 is controlled by means of a centrifugal governor. As shown in Fig. 1, the pilot circuit P, beyond the valves 15, 16, 17, opens into two branches, one leading via a valve 20 and accumulator 21 to piston assemblies 22 operating the selector lever 23 in one direction, the latter arranged to actuate a valve within the ram 37 via a rod 80. The second branch leads via a changeover valve 30 to piston assemblies 25 which actuate the selector lever 23 in the opposite direction. The valve 30 is mounted between the two plungers 28, 29 and arranged to be acutated by relative movement of the latter. A further valve 24, also actuated by relative movements of the plungers, controls flow, in a secondary circuit T, to the plungers in order to hydraulically lock or unlock them. In operation, upon a changing condition of flow through the pipe 2, say a reverse surge flow in the direction of arrow R, an increase in pressure in the pitot tube 4 and corresponding decrease in pitot tube 3 causes the valve 16 to be opened by the diaphragm 7. The reduction in pressure in the pilot circuit causes, via the valve 24, a valve 85 to open and thereby hydraulically unlock the plungers 28, 29. The valve 20, thereby causes the pressure in one of the pistons 22 to be relieved, the pressure in the other piston 22 being maintained by the accumulator 21. The selecter lever 23 is then actuated and, via the rod 80, opens a valve (fully described in Specification 860,665) in the main ram 37 and permits pressure from a primary circuit S to act on the opposite side of the ram and thus close the valve 1. Relative movement between both plungers 28, 29 causes the valve 30 to open so as to cause fluid flow to one of the pistons 25 and thereby reverse the position of the selector lever 23,and so cause the ram 37 to return in order to open the valve 1. The relative movement between the plungers may be effected from a remote position by means of a hand wheel 36 and cable connection 34, 35. A position indicator 42 is connected directly to the valve 1 by means of a cable 40.