Although failures of seam welded high-energy piping date to about 1970, the utility industry concern about premature failure of longitudinal seam welded piping has been of the utmost importance since the mid 1980’s driven primarily by well publicized piping failures at that time. The major concern is with hot reheat piping, some of which failed catastrophically resulting in substantial costs and personnel injury.
Many utilities manage their high energy piping integrity through a combination of engineering analysis and periodic inspections. At many utilities around the world, however, high energy piping has not received the attention that normally occurs after a major failure because the perception is that there have been few failures. EPRI has compiled a database of over 50 failures and large areas of damage in utility piping systems around the world and it does not include the entire utility experience but still demonstrates the need for a diligent high energy piping integrity management program.
The investigation of a recent failure in a 42 in. (1066 mm) diameter, 2 in. (50.8 mm) thick wall, ASTM A155 (American Society of Testing and Materials) seam welded hot reheat pipe demonstrated a first of its kind damage mechanism which determined that inappropriate welding filler metal was utilized for at least some of the weld passes resulting in a weldment that was weak in creep. Due to the placement of the incorrect welding filler metal, the failure occurred as a leak instead of a rupture however, the damage on the inside surface of the pipe extended for over 9ft. (2743 mm). This paper presents the results of the failure analysis and life assessment work performed and provides guidance for the rest of the utility fleet.
