The air output capacity required to achieve fast positioning in large actuators (diaphragm areas of 1,400–2,800 cm2) is too much for normal positioners, and so positioning accuracy can be compromised. A solution to this problem is a control-valve positioner package (photo), which facilitates exact positioning with fast response times over the entire operating range. The package consists of a positioner and a hook-up of several volume boosters with different output capacities. Closing and opening times of less than 2 s can be achieved over the entire positioning range. The package has proven itself for compressor bypass valves (anti-surge valves) and in petrochemical applications involving moving-bed adsorption processes. — Samson Controls (London) Ltd., Redhill, U.K.