Automatic hydraulic shut-off system

In an automatic hydraulic shut-off system having a hydraulic valve unit, a hydraulic responsive apparatus for applying a mechanical force in response to hydraulic pressure applied to said apparatus, and a hydraulic line connected between said valve unit and said apparatus, the impovement comprising a valve housing hydraulically connected with said hydraulic line and having a fluid passageway therein and a valve closure movably disposed therein for opening and closing said passageway and thereby controlling the flow of fluid in said hydraulic line, a differential pressure valve closure actuator at each end of said valve housing, two hydraulic flow sensors hydraulically connected with said hydraulic line in spaced-apart positions along said hydraulic line for receiving the flow of fluid between said valve housing and said valve unit, said sensors each having a restricted fluid-flow passageway and chambers at opposite ends of said passageways of said sensors for receiving all of the flow between said valve housing and said valve unit, and connecting fluid lines connected between said chambers of each of said sensors and a respective said valve closure actuator at opposite ends of said valve housing for moving said valve closure in said valve housing in response to an unbalance of fluid flow through said restricted fluid-flow passageways of said sensors to thereby have said valve closure close said valve housing passageway.