The invention is for a safety valve for a piping system. The safety valve has a cylindrical housing, a piston assembly with two disc-shaped pistons, each piston having at least one orifice defined therein,SAFETY VALVES a shaft connecting the pistons, a valve stem, and a stop attached to one end of the valve stem. The safety valve has a valve seat with an opening shaped and sized to receive the stop.Butterfly Valves The safety valve has a spring positioned in the housing against the piston assembly so that the spring exerts a spring force on the second piston in a direction opposite the direction of fluid flow. When fluid forces acting on the piston assembly exceed a spring force acting on the piston assembly,Resilient Seated Gate Valves the piston assembly moves in the direction of flow until the stop engages the valve seat and shuts off flow through the safety valve. An improved safety valve includes piston-actuated provisions for gradually pressurizing a fluid-actuated motor during start-up of the system, preferably by way of a changeable flow restriction. In addition such improved safety valve preferably includes a floating exhaust valve actuating apparatus movable in an exhaust closure chamber and that operates in response to the presence or absence of line pressure in the exhaust closure chamber for respectively blocking off or opening fluid communication between the safety valve's outlet port and exhaust port. A pilot operator is also included for selectively permitting or cutting off line pressure flow to actuate the piston actuator and the exhaust valve actuating apparatus. The preferred safety valve also includes a check valve for preventing back-flow from the safety valve's outlet port back to the piston actuator and back to the exhaust valve actuating apparatus.

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