A water treatment plant in Tupelo, MS has 8” Figure 118 valves from DeZURIK that have been operating every 45 seconds for 27 years; more than 19 million cycles. The valves have survived without repair all those years. Only the actuators have been repaired or rebuilt.
The valves are connected to the top of an airtight 16’ deep chamber with openings underwater at the bottom. When the valves close, vacuum pumps turn on and raise the water level in the chamber about 1.5 feet. After 45 seconds, the valves open and let air back into the chambers and allow the water level to drop back to normal, pushing water out of the openings in the bottom. That action causes a stirring effect in the water tank and keeps solids from settling.