Plug Valve Repair
All weld repairs and re-welding on plug valves must be performed by certified welders following ASME Section IX standards. Low-hydrogen welding processes are required for all welding, including repairs to existing welds. The entire welding procedure must be approved, and any repair to the main weld must be authorized by the owner before proceeding.
Before performing any casting repairs on a plug valve, the process should be completed prior to the production heat treatment. Any welding or repair work must be done before stress-relieving heat treatments. Hardness testing is mandatory for castings, especially in the weld zone, heat-affected zone, and base metal. The maximum Vickers hardness measured at 500 grams load should not exceed 310 HV.
For all repaired defects, the same non-destructive examination (NDE) method used initially to detect the issue must be applied, following the same standard. Before welding, the area to be welded should be cleaned thoroughly using appropriate tools to remove dirt, scale, or metal debris. If the defect depth reaches 20% or more of the component's thickness, no repair is allowed.
Plug valves should be installed as close as possible to the reference surface, within the available space. All above-ground working valves located at an elevation of 2100 mm or higher must be equipped with hammer pulleys that can be operated manually. The hammer pulley must use a U-type splint instead of a J-type bolt splint. Additionally, the valve must be suitable for both vertical and horizontal installation to ensure proper functionality and ease of maintenance.
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