Root causes of recovery boiler leaks

A leak in any area of the recovery boiler where water is under pressure has the potential of causing a smelt-water explosion. Understanding the root causes of these leaks will be of enormous value in guiding future efforts to improve inspections, operations, welding, materials selection, boiler design, and safety. The thousands of hours of downtime caused by these leaks provides a clear economic justification for further improvements. This article presents the preliminary results of a study encompassing the most recent 830 incidents of leaks in the recovery unit. Among the findings, the economizer accounts for one-third and the furnace walls account for one-fourth of the failures. Clearly, a more reliable design is required. Welds account for twice as many failures as corrosion. One-third of the weld failures are related to attachment welds - not butt welds - suggesting the need for a rigorous effort to improve welding techniques. Half of the corrosion-related failures are associated with general thinning and wastage, indicating the need for materials of greater integrity and designs that provide access to all areas for thorough inspection. Fatigue failures point to design deficiencies.