When selecting Norval check valves particular attention should be given to the period that the valve will remain in the open position without a flow reversal taking place.
The elastic memory of the diaphragm is time dependant and, if left open for long periods, may result in slow closure of the valve under reverse flow with subsequent leakage.
The degree of diaphragm deformation is a function of the service, temperature and material. Unlike conventional check valves, the more arduous and frequent the operating cycle the better Norval works.
Liquids – Norval check valves are designed for maximum continuous liquid velocities of 3m/sec with intermittent peak velocities up to 3.6m/sec. Where velocity conditions exceed these maximums you are recommended to fit a larger valve.
Gas and Compressed Air – Since Norval is essentially a liquid services check valve you should consult our technical department before considering for gas and air applications.