Understanding end user valve approvals Valve manufacturer's approved sub-supplier list - Part 7

摘要

Review of the valve manufacturer's approved sub-supplier list is a critical part of the end user's evaluation process. Too often issues arrive in plant operation as a direct result of poor or inadequate sub-supplier control of materials and manufacturing operations. A major end user at Valve World Americas highlighted the importance of inspection of all valve internals prior to assembly as many issues had occurred of which some were from sub-suppliers. Another example was machining issues with poor surface and stuffing box finishes noted by an end user. They discovered that the valve manufacturer sub-contracted 90% of their machining to various machine shops which were not adequately audited nor QA/QC controlled. It was claimed that "other reputable valve manufacturers use this machine shop so we thought they were alright to use". Oh dear!