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Examination of cracking in boiler tubes

Background

A manufacturer of steam raising boilers encountered a series of cracking problems in a number of boiler tubes that had seen no more than 18 months service. TWI was asked to examine some failed tubes, determine the cause of failure, and with this information make recommendations on how eliminate the problem.

  • fractographic examination of surfaces to confirm the cause and mode of failure, and
  • comparison of microstructure between failed and unfailed components was carried out. 
Micrograph of cracks in the tube wall
Micrograph of cracks in the tube wall

The cracking was found to have arisen from thermal fatigue, a result of the normal thermal operating cycle of the boiler. The material, although of variable quality, was not the cause of failure. The report concluded that the failures were a result of high thermal stresses due to poor design.

For more information please email contactus@twi.co.uk.

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