Don't misunderstand me - I like automated UT, especially for IGSCC exams, RPV seam welds and nozzle exams. The downside is the cost of automated UT vs. RT for fabrication welds that are easily accessible and the lack of suitable UT acceptance criteria for fabrication welds in the ASME code. The cost of an automated UT exam of a reactor vessel is greater than $1 million, automated UT of BWR feedwater nozzles exceeds $500,000, and a single pipe weld could easily cost $20-30,000. I don't see that being cost effective unless there is a severe hardship with doing RT, such as limited access for source or film placement, harsh working environment (e.g. radiation dose rates), or severe loss of productivity due to having to stop other work in the area while RT is performed. Also, while ASME XI has been very thorough at addressing UT personnel qualification, procedure qualification and acceptance criteria, the fabrication sections (I, III, VIII) have not kept up and don't address UT well enough to prevent the problems with overcalls. So, I'm not afraid of using UT provided it is cost effective for the specific application and suitable evaluation criteria exist.
Marty
Marty, please. I meant nothing by my statement about overcalls.
But I have seen lots of repairs being performed because clients have not adopted any form of ECA acceptance criteria. Some of these indications were so small in vertical height that they probably were not detectable by RT. However due to their length, they were rejectable.
You make a very good point, however, about the cost involved. It is expensive because the equipment is expensive as are the AUT operators.
I believe that if utilties were to invest into the reserach, and get it accepted, they could come up with alternate ECA acceptance criteria that could in the long run save them money.
By -
Date 10-10-2003 05:38
Such as is done with API 1104 Appendix A for pipelines. CTOD testing is performed to provide data for the development of alternate acceptance criteria for AUT.
Mankenberg