Alternative Well-Engineered Weld Repair Options for Grade 91 Steel

The Electric Power Research Institute (EPRI) has been actively researching the integrity of alternative well-engineered cold weld repair (i.e. no post weld heat treatment, PWHT) and low PWHT weld repair options for Grade 91 steel components. This research has resulted in the incorporation of Welding Method 6 for tube to tube weld repairs into the National Board Inspection Code (NBIC) Part 3 Repairs and Alterations, proposal of a new Welding Supplement to the NBIC Part 3 Repairs and Alterations and ignited recent discussion within the American Society of Mechanical Engineers Boiler and Pressure Vessel (ASME B&PV) Code regarding the relaxation of the current minimum allowable PWHT of 1350°F (730°C) to 1250°F (675°C) for new construction of Grade 91 steel weldments. The value of alternative weld repair procedures will be detailed in the context of destructive evaluation testing and application considerations which are discussed in a recently released EPRI Report (3002003833) Best Practice Guideline for Well-Engineered Weld Repair of Grade 91 Steel.