| 摘要 |
A gate valve is provided having a valve body with a fluid passage therethrough and a riser passage at right angles to the fluid passage. A valve gate is included for opening and closing the fluid passage. A valve stem is operatively connected with the valve gate for transmitting movement force to the valve gate. The valve stem includes a first wrench for receiving a drive member and an identically shaped second wrench head. The wrench heads are separated by a first zone of weakness formed to fail completely when a first predetermined torque is applied to the stem. Upon complete failure of the first zone of weakness the second wrench head would be exposed for engagement by a drive member to turn the valve stem. A second zone of weakness is formed on the valve stem below the first zone of weakness and is formed to fail when a second predetermined torque greater than the first predetermined torque is applied to the stem. The valve gate has a one piece body with a seal member removably arranged on the body to engage the valve body in the fluid passage.
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