The upper stem is threaded into the diaphragm retainer nut. When the handwheel is rotated to the closed position the upper stem pushes on the diaphragms, which deflect downward, forcing the lower stem against the valve seat.

• 上阀杆通过丝口旋在横膈膜止动螺母里。当手轮旋转到关闭位置，上阀杆推动横膈膜，横膈膜下垂，迫使下阀杆接触阀座。