Testing device for pilot valves

DETAILED DESCRIPTION What is claimed is: 1.
In a fluid system having a non-flowing pilot valve for controlling a main pressure relief valve having a dome and pressure responsive element therein, the pilot valve having a fluid inlet sensing chamber including a fluid inlet line thereto, a fluid outlet chamber, and an intermediate fluid chamber between said inlet and outlet chambers in fluid communication with the dome of the main relief valve; a fluid testing device for testing the functioning of said pilot valve in controlling the main relief valve, said testing device comprising: a body having a test fluid inlet adapted to be connected to a test fluid pressure source for supplying test fluid to the testing device; a fluid responsive shuttle valve member positioned within said fluid inlet line to the fluid inlet sensing chamber of said pilot valve, said shuttle valve exposed on opposite sides thereof to operating fluid pressure from said inlet line and test fluid pressure from said test inlet, said shuttle valve member movable by the higher fluid pressure between one position permitting fluid flow between the operating fluid pressure source and the fluid sensing chamber while blocking fluid flow from said test inlet, and a second position permitting fluid flow from the test inlet to the sensing chamber while blocking fluid flow from the operating fluid pressure source; and a separate valve element between the test inlet and said shuttle valve member being actuated at a predetermined high test fluid pressure from the test inlet thereby to simulate the action of the pressure responsive element in the dome of said pressure relief valve.
2.
In the fluid system as set forth in claim 1 wherein said separate valve element is in fluid communication with the intermediate fluid chamber of said pilot valve and is responsive thereto for returning the separate valve element after actuation to its initial position after the test fluid pressure is reduced to a predetermined low pressure.
3.
In the fluid system as set forth in claim 2 wherein said separate valve element comprises a piston movable between a seated position permitting test fluid to the sensing chamber and an unseated vent position permitting venting of the test fluid, said piston being exposed on one end thereof to dome fluid pressure from said intermediate fluid chamber for urging the piston to seated position