A API 579-1/ ASME FFS-1 Fitness-For-Service evaluation was performed on a steam drum pressure of a wood-fired boiler. The 30,000 pound boiler (120 psi) was overheated due to a loss of makeup water and a failure of a low-water cutoff control.
The API 579-1 standard contains very specific methodologies for evaluating pressure vessels that have been damaged or compromised due to operational or environmental factors such as fire, overpressure, corrosion, fatigue, and mechanical damage. Typical damage resulting from these factors includes pitting/loss of metal, embrittlement, residual stress, cracks, and reduced material properties. The net result is often reduced vessel integrity, shortened operating life, or even required repair/replacement. The methodology presented in Section 11 of API 579-1 / ASME FFS-1 “Assessment of Fire Damage” was chosen as the best match for the high temperature excursion of the steam drum resulting from the low water incident.
The mud drums were not included in the scope of this evaluation; preliminary inspection indicated that these drums were not exposed to a high temperature excursion.