Abstract
Pneumatic positioning actuators are very commonly used in the control of process control valves in petroleum, chemist and paper industries. During the last decade several ideas have been presented howto use water hydraulics in different applications. Low-pressure water is available in some process industrial applications a little bit the same way as pneumatic power. Lately very demanding performance specification requirements havebeen presented for positioners of process valves. In this paper requirements set to control components of pneumatic and low pressure water hydraulic drives in order to fulfil these high quality performance specifications are studied. Different experimental tests have been done with both systems and results show that the specification can be fulfilled, but quite high performance components are required.
