Low-pressure industrial boiler tubes are subject to a variety of corrosion and degradation problems. Cases and examples are described that include tube failures by pitting, corrosion fatigue and metal overheating. Careful testing and evaluation can lead to identification of the root cause(s) of these problems, and permit long-term reliable operation.
Low-pressure boilers are seldom given the attention, expertise, or economic support afforded high-pressure units, and consequently are susceptible to a number of preventable tube failure mechanisms. Procedures and practices prescribed by equipment suppliers may be suitable for routine situations, but can be insufficient to allow the operator to identify and correct for abnormal occurrences.
The most common cause of tube metal degradation is unwanted constituents in boiler water, and/or failure to adequately address those contaminants. Additional common damaging influences include excessive temperature and stress; these are often caused or exacerbated by poor water chemistry control.
