Abstract: A safety relief valve (10) has a diaphragm actuator (24) including a diaphragm (26) with a dome chamber (34) on one side of the diaphragm (26) and an underdome chamber (36) on an opposed side of the diaphragm (26). A diaphragm operated pilot control valve (38) has a valve body (46) with a pilot sensing port (54), a pilot dome port (64), and a pilot underdome port (60) in fluid communication with a pilot valve chamber (52). A slidable pilot valve member (68) connected to diaphragm (42) is mounted for movement between two pairs of opposed annular seats (80, 84 and 82, 86). Actuation of pilot valve member (68) at a low set pressure permits fluid communication of inlet fluid from pressure vessel (15) to underdome chamber (36) and exhaust of fluid from dome chamber (34) to boost opening of main relief valve member (22).

Abstract: A gas regulator valve (14) for maintaining a preset low gas pressure in a storage tank (10). A fluid balanced piston valve member (32) is seated in a closed position on seat (40). A diaphragm actuator (70) has a diaphragm (76). A linkage including opposed link arms (106, 108) is positioned between the diaphragm (76) and the piston valve member (32) and a roller (104) supported on link arms (106, 108) contacts the valve member (32) for controlling the movement of the valve member (32) between open and closed positions. The inner upper ends of link arms (106, 108) are pivotally mounted on bracket (94) secured to the housing and the lower outer ends of the link arms (106, 108) are pivotally mounted on opposed brackets (88, 90) secured to the diaphragm (76). An axial movement of the diaphragm (76) of about two inches results in an axial movement of roller (104) and piston valve member (32) of about 0.20 inch to provide a ratio of about ten to one.