NDTnet 1998 Aug, Vol.3 No.8

Abstract

It is a common knowledge that brittle fatigue failure of welded joints of pipes of various process application (steam, fuel oil, gas) and of responsible equipment occurs suddenly and leads to serious accidents with severe consequences.
The existing conventional NDT methods (ultrasonic and magnetic-particle inspection, colour fault-detection) are oriented on the search for the developed defects and need dressing of the surface. They fail to provide early diagnostics of welded joints at prefailure stage and do not guarantee reliability of equipment and safety of operating personnel.In conditions where reliability of welded joints is influenced by stress level and uniformity, distortion of geometry, structural changes in the weld, plastic deformation and other factors, a method capable of integral estimation of the joint state is required.
Now, a conceptually new method of diagnostics of welded joints has been developed and is successfully implemented in the power industry and other areas based on metal magnetic memory.The method requires no metal dressing and special magnetization (the residual magnetization of welding or earth field is used) and affords:
• determination of lines of residual stress concentration on the weld or near it - basic sourcesof damage;
• control of angle welded joints;
• establishing the necessity and quality of welded joint heat treatment,
• express analysis to be made of new and old welded joints with respect to the level and distribution of residual stresses;
• fulfillment of ferrometry functions in welds and products of austenitic and ferritic-austenitic steels.
Based on the effect of magnetic metal memory in Russia there are developed techniques to test pipes, vessels and other equipment which were approved by Gosgortechnadzor of Russia. The techniques and specialized magnetometers based on computers were implemented at more than 200 plants in Russia, Ukraine, Poland, Bulgaria, India, China, Australia.In 1997 there was a testing program Round-Robin approved for metal magnetic memory method to be included in the plan of International Welding Institute with participation of specialists from Germany and USA.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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