In-Situ Repair of Multiple Cracks Present in the RTJ Groove of High Pressure Hydrogen Bearing DHDS Reactor by Welding

This article describes a detailed repair procedure with necessary heat treatment involving the repair of multiple cracks in the Ring type joint (RTJ) groove of top man-way flange observed during the first internal inspection of the Reactor (25-R-01). Detailed site inspection and laboratory investigations, including visual inspection, thickness measurements, metallographic analysis, hardness testing of RTJ groove and RTJ gasket, Dye Penetrant testing, cladding disbonding testing by ultrasonic method, ferrite number measurement etc., were performed to identify the cause and mechanism of damage. Various factors like Stress corrosion cracking, Hydrogen induced cracking, sigma phase formation, have been involved with respect to the operating conditions of the equipment. In view of the above observations and ascertaining the severity of the overall damage of the Reactor, the in-situ repair methodology by welding was developed & repair jobs were successfully undertaken.