Quantification of Valve Stiction

Oscillations in control loops lead to poor controller performance. Stiction in control valves is one of the major causes of such oscillations. Therefore, the correct diagnosis of stiction is important. There are several methods for detecting stiction, but quantification of stiction still remains a challenge. Two parameters are used to model the stiction phenomenon successfully, namely, deadband plus stickband, ′S′, and slipjump,′J ′. It has been observed that the main cause of valve deterioration is the presence of slip-jump, ′J ′. The higher the value of ′J ′, the more severe is the level of deterioration of controller performance. Thus, in addition to the estimation of ′S′, an estimate of ′J ′ is the main challenge in monitoring the condition of a control valve. In this work a method is proposed to estimate both ′S′ and ′J ′ simultaneously unlike existing quantification methods where stiction is quantified as a single parameter.