Detection of corrosion fatigue cracking in boiler waterwall tubes using constant potential X-rays

A radiographic technique was developed to facilitate the in-site examination of the failed waterwall tubes at the coal-fired Hazelwood Power Station in Victoria. Following a laboratory trial investigation, the X-ray radiography technique was selected as being sufficiently sensitive to detect small cracks and produce a much sharper image than gamma radiography. A Scanray constant potential CPL-160 unit was obtained and adapted for site use. The radiographic parameters and procedures are described. The use of radiographic technique confirmed data from previous metallurgical examination of failed tubes. In addition to information on cracking it enabled qualitative assessments to be made on the extent of corrosion and pitting of the non-fire side wall of the tubes, thereby providing data for the overall engineering assessment of the type and extent of refurbishment work requested. 2 refs., 20 figs