Valve Magazine - Spring 2008

Full Inspection and Overhaul

A process involving a pretest, full disassembly, internal inspection and functional test is the only true way to ensure that your PSV is in the best possible condition. The pretest is performed before the PSV is disassembled. The results from the pretest are used to help gauge whether a valve would have relieved in service and at what pressure, whether it would have reseated and whether it had seat leakage. By performing a pretest and then an entire overhaul and inspection, each part of the PSV is cleaned, inspected, reused/repaired/replaced, assembled, tested and returned to service.

A certified “VR” overhaul performed by a certified repair company authorized by the National Board of Boiler and Pressure Vessel Inspectors¹is the common industry standard followed and accepted by the majority of regulatory agencies and end users throughout the

United States. In some cases, end users will accept a non-VR repair as long as it meets certain criteria spelled out within their own PSM program. While the “VR” is the preferred method, plant specific repair criteria may be acceptable with some end-users. A listing of all authorized “VR” stamp holders can be found in the National Board’s NB-18².

PROs: As stated above, a full inspection and overhaul is the only true method of determining the condition of a valve. When a valve is disassembled and inspected, it gives you a full view of the internal condition of the valve, a full visual and dimensional inspection of all internal parts, verification of the spring number and range, any potential visual corrosion or erosion, and a full functional test demonstrating consistent, repeatable

¹National Board of Boiler and Pressure Vessel Inspectors; “NBIC” www.nationalboard.org ²National Board of Boiler and Pressure Vessel Inspectors; “NB- 18” www.nationalboard.org