Attachments such as limit switches, surge controls, bypasses, speed controls, and many others have been added. More than 2500 options or combinations of options are available on a standard diaphragm operated control valve. Most problems that occur with these types of valves involve the valve seat. Cavitation at low flow causes seat wear, preventing the valve from sealing. Pressure creep occurs even when seats are still good.
Valves have trouble maintaining a drip tight seat in some static conditions.
Speed controls can cause valves to react too slowly or too rapidly to system changes, causing water hammer or pressure surges. Limit switches attached to valves should turn pumps off. If valve sticks open, pump also stays on, causing blow outs. Cycle Stop Valves solve these problems. The simple patented design of the Cycle Stop Valve always allows a minimum flow across the valve seat even when in its closed position.