Matching control valve trim with system performance

摘要

The function of a control valve is to very the flow rate in a fluid (piping) system when the position of the valve stem (valve travel) is changed. In most cases, it is desirable to have a direct or linear relationship between the flow in the system and the valve travel. Howevr, the control valve acts as a nonlinear variable resistance in the system; which itself exhibits nonlinear characteristics. Thus, the flow response, when the valve position is changed, depends on only on the valve characteristics (or "trim") but on the response characteristics of the system in which the valve is installed, the pump characteristic (which the valve is installed, the pump characteristic (which is the driving force), and the manner in which these characteristics interact. Therefore, choosing the best trim for a valve requires a consideration of the interaction of the valve, the system, and the pump characteristics.