Bulging of a tube

      Bulging is generally an indication of overheating. Continuing under the same temperature and stress conditions will eventually lead to creep and stress rupture. The amount of bulging varies with the specific metal and the type of damage, creep or overstress. If the bulge is attributed to overstress (short-term overheating), and the temperature and stress have been returned to normal, typically the life of the tube has not been reduced. Creep life will be reduced, if the bulge is the result of creep damage (long-term overheating). Bulging is considered more serious than sagging or bowing.