Confirmation of control valve stiction in interacting systems

Abstract

Stiction in a control valve generates limit cycles which can propagate to the connecting units, resulting in plant-wide oscillations and impacting the overall process performance. For stiction confirmation, Choudhury et al. [Choudhury et al., CJChE 2007;85:208-219] introduced the controller gain change method, which is based on the change in the oscillation frequency due to changes in the controller gain. In this paper, we show that this method can fail to accurately isolate and confirm the presence of the sticky valve in interacting multi-input multi-output systems. We propose a strategy based on the magnitude of relative change in oscillation frequency due to changes in controller gain to overcome the limitations of the existing method. The effectiveness of the proposed method is demonstrated using simulation studies. ©2009 Canadian Society for Chemical Engineering.