Heat treatment should be carried out by one of the following methods, ensuring that the minimum stipulated temperature is achieved through the thickness of the pipes.
Heating in a stationary industrial furnace.
Portable muffle furnace.
Resistance heaters. The method of securing resistance-heating elements around the joint should be capable of holding the elements securely in contact with the pipe work throughout the heat treatment cycle. Any fixing, e.g., galvanized wire, likely to be injurious to the joint, should not be used.
Selection of the method for heat treatment is subject to prior approval of the engineer. Manually-operated gas torches should not be used.