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M-skip®
In many industries such as oil and gas, chemical and process, there are increasing issues with the maintenance of ageing plant. One particular challenge is inspection for corrosion in areas of pipes, risers and vessels rendered inaccessible by obstructions such as supports, clamps and saddles.
Accurate inspection of inaccessible components
As visual inspection by removing clamps or lifting a pipe off its support is costly and time consuming, there is growing interest in methods which allow non-destructive examination (NDE) of these areas in-situ.
M-skip® is a new variant of the time-of-flight-diffraction (TOFD) technique and is based on angled shear wave probes, separated by the distances required to inspect wider pipe supports and clamps. The signals traveling between the probes then typically experience many reflections, or skips, between the front and back component surfaces. Measurements of the arrival times of these skip signals can be used to measure accurately the average wall thickness along the line of sight between the probes.
The presence of wall-loss flaws on both component surfaces can be detected by either loss of the skip signals, or by arc-like signals generated by scattering from the ‘tops’ of the flaws. Measurements of the time difference between the flaw signals and the associated skip signals provide quantitative information on the through-wall extent of the flaws.
Benefits
- Rapid inspection of inaccessible components such as pipe supports, saddles and clamps
- Provides quantitative upper and lower bound values for through-wall extent of corrosion/erosion flaws with accuracies of +/- 1mm or better
- Full volumes can be inspected with probes up to 1 m apart
- Sensitive to defects on both internal and external surfaces
- Very high probability of detection
- Potential for rapid screening of pipes and vessels