Potential Failure Mechanisms in Composite Tubing, 1993 Engineering Conference Proceedings

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Recovery boilers are a subject of continuing interest in the pulp and paper industry for obvious reasons: they are vital to the production of pulp and paper, they require extremely large capital expenditures, and they are subject to catastrophic failure. A simple tube leak in a recovery boiler, in addition to resulting in lost production, can devastate a boiler, while at the same time, endanger plant personnel.

In an effort to minimize the potential for tube failures in recovery boilers, composite tubing has been introduced for general use in the lower waterwall section. Composite tubing is thought to be more resistant to the deterioration produced by the extremely harsh operating conditions found in recovery boiler service. In the last several years, however, failures have occurred in composite tubing. The failures in composite tubing were due to a variety of causes involving original fabrication defects and service related deterioration.

This paper provides information regarding the behavior of composite tubing in recovery boiler service. It also describes some of the mechanisms which have the potential to produce failures in composite tubing, the programs used to determine those mechanisms, and in some cases, the corrective measures taken to return the recovery boilers in question to a level of integrity suitable for continued service.