Knowledge of Damage Mechanisms - A Key to More Cost-Effective Inspections and Repairs, 2001 Engineering / Finishing & Converting Conference Proceedings

D. C. Bennett, S. L. Meiley--This paper describes how knowing what potential damage mechanisms can occur and determining which mechanisms are actually present in process equipment - in this case, recovery boiler lower furnaces - can improve damage detection at an early stage; greatly aid in trending of damage rates, and avoid unwarranted repairs. Overall benefits of this approach are more cost- effective inspections and repairs and enhanced equipment reliability.

Damage mechanisms that can compromise the integrity of recovery boiler tubes are generally well known. Strategies for designing a well focused inspection scope and for monitoring tube damage, and methods used to evaluate and repair damaged recovery boiler tubes should be based both on the damage mechanisms in effect and on the tube’s "criticality". Critical tubes are those in which a water leak can lead, directly or indirectly, to water getting into the smelt bed.

The paper demonstrates this approach in the lower furnace section of a typical recovery boiler. However, the same principles apply elsewhere in the boiler and to other process equipment in a pulp and paper mill. Each damage mechanism is described in terms of its mechanism, how to inspect for it and typical repairs.