Fluid duct pressure regulating valve - control diaphragm failure results in valve closing against high pressure supply

摘要

A poppet valve (8) is mounted on a spring loaded (18) piston (16) by a shaft (15). The piston and spring are contained in a cylindrical housing (11) of slightly greater diameter than the piston. A flexible diaphragm (14) connected to the piston seals off the spring housing from the fluid duct (5, 6). The pressure in the upstream manifold (5) acts in opposition on the areas of the valve (d1) and diaphragm (d2) which are equal. Valve position is thus independent of upstream pressure but does depend on spring setting (21) and downstream pressure. The piston area (d3) is greater than the active diaphragm area (d2) so that if the latter fails, the piston is forced up and the poppet valve closes. Orifice (22) prevents pressure building up on the upper side of the piston and restricting its movement.