MTM and MFL DATA COMPARATIVE VERIFICATION
ACCORDING TO 100% NDT DATA
of metal of the gas pipeline section exposed along its total length
In 2016 in order to evaluate the data of various methods of diagnostics of gas mains, PJSC GAZPROM conducted an МТМ survey, in-line inspection (MFL) and continuous NDT of the 8 km. section of the gas-main pipeline lifted from the trench.
The results are reflected in an all-in-one scale of the linear coordinates in the diagram below. 100% control of metal over the fully prepared surface confirmed the high efficiency of the MTM. The recorded detection of metal defects of different nature was better, as compared to the MFL. Just three sections (marked by arrows) were not detected by the MTM: 1. a metallurgical rejection (a crumbled out skin of 10 × 10 × 3.0 mm with the film of corrosion); 2. two SCC defects in the fissuring field [11360 × 50 × 1.0 mm; 450 × 500 × 1.0 mm; 50 × 50 × 1.0 mm]; 3. a defect [100 × 100 × 1.0 mm].
Fig. Distribution of anomalies detected by the MTM, the MFL and at the 100% NDT of the metal:
1 - Non-essential defects that do not require repair; 2 - Defects requiring; 3 - Defects requiring pipe cutting / replacement (first-priority repair) according to the PJSC GAZPROM regulations. The arrows indicate defects not detected by the MTM.