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straight, membraned roof tubes of aboiler. These instances appear to beassociated with the type of internalcorrosion-fatigue damage that is de-scribed in PSB-29, and points out theimportance of regular and diligentinspection of the internal surfaces ofareas known to be susceptible to thistime dependant, damage mechanism.

InspectionThe most effective method of detect-

ing corrosion fatigue damage is IDvideoprobe inspection, though thismethod does not allow for direct deter-mination of crack depth. Other non-destructive methods can also be em-ployed, such as radiographic examina-tion and angle-beam ultrasonic inspec-tion, but these methods require thedevelopment of procedure and accep-tance criteria.

Recommendations forImmediate Action

Review boiler arrangement draw-ings for areas that would be suscep-tible to pipe and tube flexing dur-ing boiler cycling. Pay attention toareas between generally inflexibleand rigid penthouse componentsand the boiler proper. Target theselocations first and prioritize thoseareas as most susceptible to damag-ing corrosion fatigue.

Thoroughly inspect bend areas inriser and supply piping, such asthose described above.

Review waterside operating historyto determine if oxygen, pH orchemical cleaning excursions haveoccurred. Such excursions would

increase the probability that corro-sion-fatigue damage has occurred.

Review pressure part failure historythat may indicate increasing suscep-tibility to corrosion-fatigue failuresand revise tube inspection proce-dures and frequencies accordingly.

Replace any tubing that shows anyevidence of cracking as soon aspossible.

B&W SupportContact B&W Field Engineering

Services through your local districtservice office for assistance in yourinvestigation and inspection efforts toidentify and locate corrosion fatiguedamaged tubing and to obtain copies ofPSB-2 and PSB-29. B&W can be particu-larly helpful in evaluating the specificboiler details and determining areas ofgreatest risk to target for further inspec-tion and study. B&W also possessesunique and effective non-destructivecapabilities that may uncover ID crack-ing problems.

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Photo shows catastrophic tube rupturethat is possible with corrosion fatigue.

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