NS Two-Stages, cushioned closure check valve
Developed to eliminate pressure slam of check valves, frequently found in roof-tank filling pumps of high-rise buildings. It opens on pump start, and closes at controlled pace when the pump stops.
The NS valve is located at the pump discharge (or on the common manifold of the pumps outlet), and is fullyopened through normal operation of the pump.
When the pump stops, and flow rate drops to nil, the valve starts closing. But unlike a standard hydraulic check valve that closes slowly from full- opening to fullclosure, the NS valve closes fast (within 2-4 seconds, depending on it`s size) to approximately 20% of its fullopening stroke (“Fast closure period”). By this time the returning flow is reduced to a negligible value.
Then, the closure pace of the NS valve is decreasing to a slower, adjustable speed (“Slow closure period”). This restricted movement of the valve trim generates a non-slam seating.
The described procedure does not require any electrical command and interlink between the valve and the pump as the device is activated automatically by the hydraulic parameters of the system.