Trip throttle valve

摘要

A trip throttle valve with a manual exerciser and combination of a hydraulic piston and a biasing force bearing sleeve is provided in place of a piston. The piston is not directly connected to a valve stem and the sleeve is threadably engaged with the valve stem so as to cause relative axial movement between the sleeve and the valve stem when the stem is rotated through the manual exerciser. The hydraulic portion of the valve is provided with a by-pass passage so that the piston is made axially movable toward the sleeve under the pressure which occurs when the by-pass passage for the hydraulic liquid is blocked but the piston is arrested at a certain axial position where the by-pass passage is still blocked and the axial movement of the sleeve is restricted against the piston. Blocking of the by-pass passage is arranged to take place after the axial separating distance between the sleeve and the piston reaches a predetermined value so that any inadvertent movement of the valve stem by the engagement of the piston with the sleeve is avoided.