PERFORMANCE OF ULTRASONIC INSPECTION IN THICK-WALLED PRESSURE-VESSEL FABRICATION

This paper summarizes the practial experience gained by Head Wrightson Teesdale Limited as a result of the detection in late stages of manufacture of buried weldement defects during ultrasonic inspection of two vessels in microalloyed C-Mn steel destined for high pressure service. Following ultrasonic examination, samples containing reported defects were removed for metallurgical investigation and the results of the examinations showed considerable variance to the ultrasonic test reports in terms of defect presence, characterization, size and location. Evaluation of the observations made indicates far greater uncertainty in the sizing of small defects than is generally recognized and this finding is discussed in relation to the acceptable criteria in BS. 5500.