In order to improve the surface quality assurance of the pipe, Nippon Kokan K. K constructed the magnetic particle flaw detection equipment for the complete outside and inside surface of the pipe.
Magnetic particle inspection has been used for a long time, but not a few techniques have depended on customary practice. Then, we investigated theoretically diffusion of magnetic flux and method of evaluation of residual magnetism.
The results obtained are summarized as follows:
(1) The theoretical model for a calculation of residual magnetism is made.
(2) The new method of evaluation of residual magnetism by artificial defects is established.
The magnetic particle flaw detection equipment for the large diameter pipe, that was installed based on the previous investigations, has been running favourably since June 1983.
