Partial stroke valve test apparatus
This invention relates to an emergency valve shutdown system having an integrated test facility. The invention provides an apparatus for testing emergency shutdown valves in a process industry comprising: a valve having a plurality of limit switches each limit switch arranged to indicate that the valve has reached a corresponding one of a plurality of predetermined valve positions; a valve monitor module arranged to send a signal to said valve to initiate movement of said valve and to receive feedback relating to said limit switches; wherein said feedback is provided via a single feedback signal between the valve and the valve monitor module.
1. An apparatus for testing emergency shutdown valves in a process industry comprising:
a valve having a plurality of limit switches each limit switch arranged to indicate that the valve has reached a corresponding one of a plurality of predetermined valve positions, wherein each of said plurality of limit switches closes a path through one of a plurality of resistors arranged in parallel to provide a discrete valued voltage in dependence upon a number of limit switches which are closed;
a valve monitor module arranged to send a signal to said valve to initiate movement of said valve and to receive feedback relating to said limit switches;
wherein said feedback is provided via a single feedback signal between the valve and the valve monitor module.
2. An apparatus according to claim 1 , in which the predetermined valve positions are fully closed, partially closed and fully open.
3. An apparatus according claim 1 , in which the valve is a pneumatic valve.
4. An apparatus according to claim 1 , in which the valve monitor module is arranged in operation to send a signal to the valve to terminate the test if said feedback signal indicates a one of said plurality of predetermined positions has been reached or if a predetermined time limit is reached.