How many times may a welding repair of a heat exchanger be made without prior approval?

The correct answer is based on the regulations that govern the repairing of heat exchangers in the context of oil fuel installations. According to the standards established by the Maine Journeyman Oil Fuel Board, a heat exchanger can only undergo a welding repair once without obtaining prior approval. This regulation is in place to ensure the safety and integrity of the system, as multiple repairs can compromise the pressure vessel and potentially lead to hazardous situations. By limiting the number of unapproved repairs, it encourages professionals to seek the necessary oversight and adhere to safety protocols, ultimately protecting both the system and the environment.