Ed H. Edwards is the vice president for HBE Engineering of Three Rivers, Michigan, a supplier of centrifugal pump minimum flow valves and orifices. He has worked in the pump and related equipment field since 1972 and has a B.S. from Western Michigan University.
The ARV operates without air or electric power and can be installed with three piping connections, on or near the pump discharge, just as an ordinary check valve would be. On pump startup and without process demand, the bypass is completely open, recirculating the necessary minimum flow. Once process demand begins, the spring-loaded disc is lifted and held in position by flow demand. Until main flow demand exceeds recommended minimum flow, the valve will bypass enough flow so the sum of the process flow and the bypass flow equals or exceeds minimum flow. As the main flow demand increases beyond recommended minimum flow, the bypass will close, and all flow will go to the process.
When using ARVs, operators must follow the manufacturer’s instructions regarding flow direction, spacing from pump discharge and straight pipe requirements. Once ARVs are installed and insulated, they should not be forgotten. To prevent untimely failures, users should follow the manufacturer’s inspection and maintenance procedures.
Recommendations for a Reliable System
Determination of a pump’s minimum flow must be taken seriously, and a reliable system should be incorporated with every new pump installation.
Users should review installed pumps with higher-than-expected failure rates and/or maintenance requirements for proper minimum flow protection.
When investigating minimum flow equipment needs, end users should consider doing the following steps:
- Head off problems by making sure the conditions of service that end users provide to their suppliers are as accurate and complete as possible.
- Check out a supplier’s experience with similar applications and be sure to ask about their reliability and service.
- Demand that the valve or orifice you purchase be tested to assure proper performance. Documentation of the “as-tested Cv” should be available for review at your convenience.
Protecting your company’s investment in its centrifugal pumps can greatly influence its profitability through improved reliability, fewer replacements, a decrease in the amount of costly pump reconditioning expenses and less disruptions in production activities.
I.J. Karassik. Pump Handbook, McGraw-Hill, 1986
I.J. Karassik. Centrifugal Pump Clinic, Mercel Dekker Inc., 1989
E.H. Edwards. Pumps & Systems, March 2003