Patent GB-862744-A (GB)
Title: Improvements in or relating to hydraulic safety valves
Inventor: ORLOFF GEORGE
IPC: F16K17/10
Filed: 1956-03-19
Abstract: 862,744. Valves; fluid-pressure servomotor control systems. ROTOL Ltd March 19, 1957 [March 19, 1956], No. 8558/56. Class 135. In a safety valve transient pressure pulsations are absorbed by movement of the seat and the closure member. The closure member 15, Fig. 1, is integral with a spring-loaded plunger 13 and seats on one end of a sleeve 17 movable in a bore in a partition 18 between two chambers 21, 12, respectively connected to the inlet and outlet 22, 23 of the housing 11. When the inlet pressure rises above a predetermined value the sleeve 17 and the closure member move against the pressure of the spring 24 until the flange 20 of the sleeve 17 abuts the partition 18. A continued increase in pressure moves the closure member 15 from its seat and fluid passes through the plunger orifice 16 to the outlet 23. At a particular rate of flow the orifice 16 gives rise to a pressure drop sufficient to effect further movement of the closure member 15 away from the seat. A light spring may be interposed between the plunger 13 and the sleeve 17. In another example, Fig. 4 (not shown), the orifice 16 is replaced by a ring of ports controlled by a spring-loaded flat ring valve. In another example, Fig. 5, the orifice 29 which effects the high lift for high rates of flow through the valve is at the outlet 30 of the chamber 12. In this case there is free flow round the valve plunger. In another example the plunger is similar to that of Fig. 5 but the stem is acted on by a spring-loaded detent. When the valve lifts it initially has to overcome the action of both the valve spring and the detent but once opened can continue its lifting travel against substantially only the action of the valve spring. The valve of Fig. 7 is the inversion of that of Fig. 1 and operates in the same way. The closure member 121 passes through a bore in a partition 119 between the chambers 123, 116 connected respectively to the inlet and outlet 124, 117 and seats in a port 113 in the spring-loaded plunger 112 having an orifice 112c which, if the flow rate is high, causes the pressure drop and the necessary increase in pressure to effect a high lift of the valve seat member. In another example, Fig. 8 (not shown), a safety valve of the Fig. 7 type is mechanically connected to a piston valve which is moved upon operation of the safety valve to open a large bore exhaust passage. The valve of Fig. 7 may be the first stage of a two-stage arrangement, Fig. 9, the second stage of which comprises a valve 140. When the first stage valve operates as described above the second stage valve 140 over-balances and opens to allow a large fluid flow to tank. A safety valve of the type described above may be located in parallel with a conventional safety valve and a selector or cock provided to allow selection of one or other valve to effect control. The second safety valve is unnecessary if the orifice which effects the high lift opening of the valve is no longer provided through the plunger but in a separate passage and is controlled by a solenoidactuated valve member. When the solenoid is de-energized the valve member is positioned to provide a small orifice and the safety valve operates with the high-lift characteristic as described above. If the solenoid is energized the valve member is withdrawn from the orifice and the safety valve operates in the conventional manner.