FLUID PRESSURE MONITORING SAFETY SYSTEM

摘要

A shut-off valve in a fluid line closes by spring pressure and/or line pressure and incorporates a control chamber wherein pressurized control fluid acting on a piston opens the valve in opposition to the spring pressure and/or line pressure. A 3-way actuator pilot normally places the control fluid in communication with the control cylinder but when vented cuts off the control supply fluid and releases the pressurized control fluid from the control chamber to cause the shut-off valve to close by spring pressure and/or line pressure. A monitor pilot responsive to pressure changes in the fluid line incorporates a relief valve and opens the relief valve by cam action to vent the actuator pilot whenever the pressure in the fluid line makes a predetermined departure from a normal pressure range.