PILOT OPERATED RELIEF VALVE
A pilot operated safety relief valve (14) in which a pilot valve (32) controls the opening and closing of the main valve member (26). The pilot valve (32) has a spindle valve member (70) between an intermediate dome fluid chamber (52) and an exhaust chamber (54) communicating with exhaust port (52) and exhaust line (38). Spindle valve member (70) has an annular sealing mem-ber of membrane (104) having a relatively thin body (105) with op-posed beads (106, 108) along inner and outer peripheries of body (105) for sealing between spindle valve member (70) and the ad-jacent retainer sleeve (94). Any positive backpressure forces from exhaust line (38) are balanced against spindle valve member (70) by annular seal (80) and membrane (104). Membrane (104) is effective for sealing between spindle valve membre (70) and retainer sleeve (94) without generation of frictional forces therebetween thereby to permit precise actuation of main valve member (70) within the tol-erance of the relieving pressure specified for pilot valve (32).