Abstract: A pilot valve mechanism for controlling the flow of a pressure medium responsive to predetermined variations in a pressurized system. The pilot valve mechanism is constructed in such manner that a plurality of pilot valves may be connected in assembly and may be operative to shut down operation of a flow system responsive to sensing of pressures that are above or below a predetermined range of operating pressure.Each of the valves may include a shuttle valve mechanism capable of interrupting fluid communication between the inlet and outlet of the pilot valve mechanism or between the outlet and vent of the valve assembly, depending upon the position of a shuttle valve actuating piston that is proportionally movable responsive to variations in the pressure that is sensed by the pilot valve mechanism. Movement of the piston and shuttle valve to the various positions thereof may be controlled by an urging means that may be adjustably preset for a particular high or low pressure.

Abstract: A test valve is positioned to block off a primary fluid pressure source acting on a pilot valve means and to provide communication with an alternate test fluid pressure source for testing the pilot valve means. The test valve has a central bore in which a depressible plunger is positioned for longitudinal movement between a seated extended position blocking the primary fluid pressure source and simultaneously commmunicating test fluid to pilot valve means, and an unseated retracted position in which the alternate fluid pressure source is sealed and blocked by an annular sealing member. The plunger has the annular sealing member adjacent its inner end in sealing contact with the adjacent surface forming the bore and positioned inwardly of a discharge passage in the plunger for the alternate fluid source. A hollow detachable stinger member which seats the plunger provides the test fluid and has a manual control thereon which selectively supplies the test fluid to the test valve.

Abstract: A control valve for a fluid actuator has a slide valve member mounted within a housing with an external knob on one end and a piston on the other end. The knob may be manually operated for resetting the piston. When the main flowline pressure reaches a high or low pressure outside the fluid pressure operating range the piston is seated and fluid is exhausted from the actuator for effecting movement of the main valve member. The control valve is maintained in its exhaust position by a spring continuously urging the piston into a seated position. An annular seal engages the face of the piston in seated position to expose only a relatively small surface area of the piston to fluid pressure when the piston is seated and the control valve is in an exhaust position. Means are provided to permit a venting or bleeding of fluid around the piston in the seated position of the piston in the event of leakage of fluid past the annular seal or temporary unseating of the piston resulting from vibrations or the like.