| 摘要 |
On a liquid cargo tank of a barge, a pressure responsive pilot valve operates through a combination of levers to unlatch a main valve clamp arm. One lever is a latch arm having a first position engaging and retaining a latch stud mounted on the clamp arm, and having a second position free of the latch stud whereby the clamp arm is released. A latch hook normally retains the latch arm in the first position but is operable to a second position to free the latch arm from the restraint of the hook. A pilot-operated trigger arm is operable on the latch hook to move the latch hook from the latch arm retaining position to the latch release position. The trigger arm also is able to directly engage the latch arm for unlatching it if not already unlatched immediately upon freedom from restraint of the hook. The main valve seal disk is held closed under a spring-load by the clamp arm. The minimum valve closing load on the main valve is established by a high rate spring having a predetermined load and which is further loaded upon placement of the clamp arm in the latching position. Means are also provided to facilitate field testing of the valve-opening set point pressure.
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