We designing a bildge-ballast system for a ship River and selected valves duo check for suction lines (Low weigth). Crane Duo Check valves were select in ASTM A395 with metal seat and interior stainless steel . They came to the worshop and the officers performed a "proof of tightness," water without pressure on the side of the springs and found that the fluid is not retained.They are determined to return the valves to the supplier (Crane-WO supply), but I'm not sure that this is a good practice to test the tightness of the valve.Any check-valve, both soft and metal seated, will require a certain amount of pressure to reach the factorys stated closure thightness. (This will for softsealed valves (non-metal closure) often be in the range of 2 meter water column. - I have not checked Crane metal seated, but cannot imagine this to be below 1,5m???)The factory will be able to give you precise information on the important facts here:a) Required pressure (water column) for thight closureb) Rate, specification ond explanation on how thight and how to test and measure for max and min pressure.c) Information on test procedure at factory and if every valve is tested or not-d) Any generalcertification on the valve (Lloyds, Veritas etc.) approval, material and pressure test certification.If theese points concur with the buyers inquiry, and no extra test is required or mentioned, the question is still if the test done at yard can be accepted by the supplier and factory.

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