Case Study of Check-Valve Slam in Rising Main Protected by Air Vessel

Check valves usually are fitted on pump-rising main systems to prevent the development of backflow when a pump cuts out. Frequently, air vessels are used in such systems to control transient pressures resulting from pump start and stop. The presence of an air vessel adjacent to a check valve may cause the valve to close, after pump cutout, with a sharp impact, typically producing an audible valve-slam sound. The phenomenon of check-valve slam is undesirable, because it can result in damaging pressure transients. A case study of a pump-rising main system, protected by an air vessel, which experienced the problem of check-valve slam, was investigated. Both field measurements and numerical modeling (using a spreadsheet) of the system were conducted.