Improving the Performance of Pressure Reducing Valve Using Two Stages

Abstract

Control valve is required to control flow or pressure of fluid flowing in piping systems. In the present work, experimental measurements are reported for flow characteristics of single stage and two stage control valves are reported under non-cavitating and cavitating conditions. A test rig was constructed to test valve performance at the Faculty of Engineering, Ain Shams University. The test rig of the experiment consists of a vertical, multistage inline centrifugal pump driven by variable speed motor, piping system, flow meter, pressure gauges, differential pressure manometer. Water is recirculated to a large water tank 25 m3. Insertion type magnetic flow meter the effects of diameter ratio and spacing between the two stages are examined. Four single stage valves and five alternatives of two stage valves are investigated. The results show that the pressure loss coefficient is inversely proportional to the distance between the two seats in the two stage valves. Cavitation occurrence decreases if the area ratio of the valve is reduced and the distance between the two stages decreased. The inherent characteristics of the valve are also affected by the geometry parameters of the two stage valve. Keywords: cavitation – two-stage valve – pressure control