We have a low temp CS pipeline carrying liquid ammonia at minus 33 Deg, these pipes were found with "lamination defects" which were considered to be acceptable from design view point. These defects were marked on the pipelines and need to be monitored for their growth on regular intervals form outside. We had initially welded some probles along these defects and had measured the growth using LCPD technique. It seems the LCPD doesnt work and we need to resort to some other technique, all other NDT methods such UT or MPI are not suitable as these require insulation removal which is not possible beacuse of sub zero temperature of medium. Does any one know about a suitable NDT method that can be employed to monitor these defects.
regards
regards