| 摘要 |
The gate valve has a shutter (3) which is normally operated by a handwheel (6), with its rod (5) connected to the shutter by a control shaft (4) and a shearing pin (22). The shaft passes through a chamber (8) and has a ring (19) which acts as a piston during emergency operation of the valve. In an emergency, gas from a tank (31) mounted on the outside of the chamber is fed into it through an aperture above the ring. The pressure of the gas applied to the ring shears the pin, separating the shaft from the handwheel control rod and driving the shaft and shutter down to close the valve.
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