We are having really very tough time while producing small metal seated ball valves fire pumpsin the range of 3/4" class 150(Floaters) to 2" class 300(trunnion).we have done all permutation and combination but unable to achieve zero leakage as per API 598. these valves are for produced water package with a design temperature of 100 deg centigrade max. even we replaced stellite coating with tunsten carbide coating on Split case pumpsball and seat every efforts is in vain. we disassembled and did some manual lapping that worked a bit on trunnion but floaters are still unresolved mystery. these are basically carbon steel cast valves with SS trim too many factors to pinpoint the cause of your problems. Our suggestion would be "as a starter" to check exactly where the leakage occurs, if it is always the same point/component that gives leakage. Are the componentsVacuum pumps visibly damaged/deformed when valve is disassembled for repair (again are they damaged in same point/way). Once this is established & if it is In-line pumpsalways the same problem, We would look at design against materials received & used. Have to introduce some kind of logic/repeatability to your trouble shooting, your R&D team along with your Q.A. should put down a Magnetic pumpstest, disassembly, component check & report procedure to follow repetitively.

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