Valve Status Monitoring

A valve apparatus has a valve ( 1 ), an actuator ( 2 ) and a leakage sensor ( 3 ). A body ( 4 ) of the valve has first and second valve chambers ( 6, 8 ) connected to respective valve ports ( 10 & 12, 14 & 16 ) and joined by an intermediate passage ( 18 ). The valve can be set by the actuator to any one of three valve configurations. In an 'open' configuration the intermediate passage is open to interconnect the first and second chambers. In a 'closed' configuration, the intermediate passage is closed by first and second seals ( 24, 26 ) seated at respective locations in the passage to seal respectively between the first and second chambers and a leakage chamber ( 28 ) at the portion of the intermediate passage between the two seals. In a 'cleaning' configuration one of the seals is unseated to connect a respective one of the first and second chambers to the leakage chamber, while the other seal remains seated. The leakage sensor is connected to the leakage chamber to provide a signal indicative of a leakage flow from the leakage chamber.