| 摘要 |
<p>A multi-mode pressure relief valve includes a body having fluid inlet and outlet ports and a compressed gas inlet port. The fluid ports and gas port isolated from one another. A reciprocating piston is in communication with the gas port. A valve stem is movable between an open condition and a closed position to permit and stop flow communication between the fluid ports. A spring is disposed between the valve stem and the piston and urges the piston and valve stem away from one another. The valve is operable in at least three modes, an operating mode in which the valve is open, the stem is spaced from the piston, and the piston applies pressure on the stem, and in which the pressure is balanced by fluid pressure the inlet, a zero-state mode in which the valve is open, the stem is spaced from the piston, the spring is in a relaxed state, and the piston applies no pressure on the valve stem, and a relief mode in which the valve is open, the stem contacts or is in close proximity to the piston and the spring is in a compressed state due to the fluid pressure.</p> |
