Pipeline Crack Detection Technologies

[TheElv]

Hello,

I occasionally review pipeline integrity management systems for various natural gas or hazardous liquid lines in HCAs (High Consequence Areas). I'm aware of the limitations that standard MFL inspection tools have with regard to crack detection and for a pipeline operator to be confident about picking up axial cracks, stress corrosion cracks etc. from internal inspections (rather than hydrostatic testing, different pigging technologies are available such as EMAT, CMFL, ultrasonic etc. I'd be interested in opinions on the relative merits of the different technolgies that are available today and whether there is any research that has compared them in terms of crack detection effectiveness / false positives etc.
Many thanks.
Jon

 

[brimmer]

I am not sure there has been any true research in POD between tool types. I can give you my experiences.

UT - best at the moment, highest numbers in terms of POD, POI, analysts have gotten better over the last few years. Still some issues with missing some cracks, identification, and longseam geometry issues. I have summarized some numbers below from a large UT dig program I just completed.

EMAT - not enough pipe run yet, only available in larger diameters. First generation EMAT runs detected no cracks, all false positives (internal fab anomalies). Tools are much improved now and detecting cracks.

TFI - useless, shouldn't run these for cracking, will only detect very large gaping cracks, and POI is also low.

UT numbers from dig program:
330 anomalies dug. The POD was 100% for the program, in that there was always some sort of anomaly present, but the POI was lower, and varied as for anomaly type. POI for crack field 0%, POI for crack like 59%, POI for notch like 71%. We found 47 anomalies not detected by the tool during the digs, but all were at or below the depth reporting threshold (1mm in this case). As far a sizing, the tool genrally overestimated the depths and lengths, which is a good thing. We did have more anomalies actual depth go over the reported depth bin in the lower depth ranges, 0-1mm & 1-2mm, and none over in the 2-3mm bin.
The POD & POI will vary as far as tool vendor, I have my favorites but can't really expand on that in this forum.