Page 163 - Valve Selection Handbook

150 Valve Selection Handbook

However, the speed with which forward flow retards can vary greatly
between fluid systems. If, for example, the fluid system incorporates a
number of pumps in parallel and one fails suddenly, the check valve at
the outlet of the pump that failed must close almost instantaneously. On
the other hand, if the fluid system contains only one pump that suddenly
fails, and if the delivery line is long and the back pressure at the outlet of
the pipe and the pumping elevation ^re low, a check valve with a slow
closing characteristic is satisfactory.

Figure 4-13. Diaphragm Check Valve with Ring-Shaped Pleated Diaphragm.
(Courtesy of VAG-Armaturen GmbH.)

Figure 4-14. Diaphragm Check Valve, Incorporating Flattened Rubber Sleeve
Closure Member. (Courtesy of Red Valve Company Inc.)