Capacity testing and local flow analysis of geometrically complex trims installed within a commercial control valve

Abstract

Industrial control valves often handle flows with very high pressure drops (conditions often referred to as severe service). In order to cope with these pressure drops, geometrically complex valve trims with many stages of pressure loss, are designed to prevent undesirable side effects such as cavitation, excessive noise or erosion. These effects are maintained under control by gradually decreasing the pressure in each stage of pressure letdown of the trim. There are many different product designs for control valve trims produced by different manufacturers. One such design uses cylindrical obstructions in the flow field to control the pressure drop. The design of these trims is based on their capacity (Cv) values. With the advent of advanced computational tools, such as Computational Fluid Dynamics, it has become possible to test these trims in flow conditions which are difficult to achieve in laboratories, but do exist in real time functioning of the trims. Hence, this study presents capacity testing and local flow analysis of a complex geometry trim, installed within a commercial control valve for severe service. The results show that the capacity of this particular design of trim decreases as the valve opening position decreases.