Application of Constant Flow Rate Control Valve in Pump Discharge Regulation

Abstract

Accurate volumetric water delivery is key to fairly distributing water in pressurized systems. Discharge control valves facilitate water monitoring and management in pressurized networks. In this study, the application of a mechanical choked orifice plate (MCOP), also called a discharge control valve, is illustrated in pump discharge control. A MCOP includes a float-spring blockage system inserted into an ordinary orifice that maintains a quasiconstant flow by being insensitive to both upstream and downstream pressure fluctuations. The design principle of a MCOP is revisited in this study. A general discharge-differential pressure formula was developed for a cylindrical orifice configuration, based on which an initial design method was proposed to estimate the float shape line for the design discharges of 5 and 10 l/s. Then, MCOP performance was improved by adjusting the spring precompression. Experiments were performed to investigate the hydraulic behavior of a MCOP in a variable speed pumping system. The results indicate that the MCOP can adjust the operating point of the pumping system to keep an almost constant flow rate. Furthermore, the application of MCOP for regulating a single pump with constant rotational speed was studied. It is found that a MCOP is a useful tool to regulate the pump operating point at the highest efficiency even if the total head loss changes in the system.