Authors: A. Srinivasan; Rames C. Panda
Addresses: Department of Chemical Engineering, CLRI (CSIR), Adyar, Chennai – 600 020, India ' Department of Chemical Engineering, CLRI (CSIR), Adyar, Chennai – 600 020, India
Abstract: It is widely known that most of the chemical and biochemical systems are complex in nature due to presence of non-linearity in input-output behaviour or inherent non-linearity of certain accessories, specifically in actuators, like control valves in an industry. The actuators of control systems, i.e., pneumatic control valves, play important role in exhibiting complex behaviour that cannot be modelled using simple linear dynamics. With progress in time, the control valves show unusual behaviour between its inputs and outputs mostly due to stiction, hysteresis and dead-band non-linearity. Experimental results on several control valves show continuous degradation in loop performances. A theoretical model based on statistical analysis of steady state data of manipulated variable (MV) is formulated to predict maintenance requirement around the control loop. The theoretical model is validated using experimental data obtained from particular process industry.
Keywords: control valves; actuators; statistical analysis; stiction; nonlinearity; modelling; maintenance requirements; control loops; static friction; valve performance.
International Journal of Instrumentation Technology, 2012 Vol.1 No.2, pp.93 - 102
Received: 08 Sep 2011
Accepted: 04 Jan 2012
Published online: 17 Sep 2014 *