Looking for 3" duo check valve fire safe tested to be used with seawater class 150. I would be loathe to use a valve of this type on sea water service without a thorough evaluation of materials and dynamic behaviour. I have experienced spring & pin failures in sea waater. On one gas platform one half of the disc disappeared. Check out the nuclear regulatory reports of failures of this type of valve. Corrosion can occur in stagnant areas even with super duplex materials. In desalination plants we specify super duplex annulus type check valves from Noreva or equivalent. Check out Fluid Transients in Pipeline Systems by ARD Thorley and also Delft laboratories re dynamic behaviour of check valves and how poorly these perform without strong springs. Of course heavy springs increase head loss .

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