GB846033A - Safety-valve - Google Patents

Abstract

846,033. Fluid-pressure servomotor-control systems. CHARASSE, A. F. Oct. 17, 1957 [Oct. 18, 1956], No. 32456/57. Class 135. A safety-valve for a steam boiler controlled by an auxiliary valve acting through a relay valve, comprises a valve body 23, Fig. 2, housing a valve member 32 normally held on its seat 24 by pressure transmitted to act on a piston 27 through a connection B connected to a remotelydisposed detector unit, Fig. 3, having connections A, J to a pressure source indicative of boiler pressure and exhaust respectively. Connection A may be to the steam or water spaces of the boiler or by means of a steam trap to any other pressure source to actuate the piston 27, Fig. 2, without the consumption of steam or water from the boiler. The detector unit comprises an auxiliary valve 10, Fig. 3, having slight axial movement with respect to a piston 8 loaded by a spring 7a and a relay valve 21 normally held closed by pressure from the connection A through a pipe E which opens a needle valve 20. On boiler pressure rising above a value determined by the spring 7a, the piston 8 is raised to first close a vent passage H and then unseat the valve 10 so that pressurefluid is admitted to a space b above a piston 13 to move this piston downwardly against its loading-spring 17a and with lost-motion move a plunger 18 to unseat the relay valve 21 and close the needle valve 20. Pressure fluid above the piston 27 is now exhausted through the connections B, J whence boiler pressure acting on the valve 32 unseats this valve to relieve boiler pressure.