Improved methods for sizing metal loss in dents for ECA



Published May 31, 2020
Rhett Dotson Fernando Curiel Luis Sacramento Zach Locks Jacob Duska


Dents interacting with metal loss remain as a significant challenge to operators. Existing regulations require that dents with metal loss within high consequence areas be treated as immediate repairs or 60-day conditions, resulting in costly excavations for many operators. At the time when these regulations were written, it was not clear whether inline inspection technologies could discriminate the nature of the metal loss (i.e. corrosion or mechanical damage) or provide accurate sizing. Furthermore, advanced analysis techniques such as finite element analysis were limited, and fitness- forservice evaluations were not common. While the technological hurdles involved with evaluating interacting dent and metal loss features have been overcome, sensor lift-off remains a challenging issue for magnetic flux leakage (MFL) inspection tools, as sizing accuracy degrades at larger lift-off distances. Until recently, the sensor lift-off issue limited the ability to perform fitnessfor- service evaluations because the metal loss in dent features could not be confidently sized. This study demonstrates how integrated lift-off sensors can be used to quantify the lift-off as the MFL sensors pass over a dent. This technology integration has allowed the confident application of sizing specifications for many dents with metal loss, thereby permitting robust fitnessfor- service evaluations. Several case studies are examined in this paper, demonstrating how the integrated MFL and lift-off technology can serve to reduce excavations while still ensuring safe pipeline operations.

How to Cite

Dotson R, Curiel F, Sacramento L, Locks Z, Duska J. Improved methods for sizing metal loss in dents for ECA. PST [Internet]. 2020May31 [cited 2020Aug.8];4(2(4):126-3. Available from:


Download data is not yet available.
Abstract 1 | PDF file Downloads 3



Pipeline anomalies, metal loss, dent inspection, magnetic flux leakage inspection, fitness-for-service evaluation.

[1] Code of Federal Regulations, Title 49, Part 192, Transportation of Hazardous Gas: Minimum Federal Safety Standards, U. S. Government Printing Office.
[2] Code of Federal Regulations, Title 49, Part 195, Transportation of Hazardous Liquids or Carbon Dioxide: Minimum Federal Safety Standards, U. S. Government Printing Office.
[3] ASME B31.8-2018, Gas Transmission and Distribution Piping Systems, ASME Code for Pressure Piping, B31, 2018 Edition, The American Society of Mechanical Engineers.
[4] Tiku, S., Eshragi, A., Rana, A., Dinovitzer, A., PRCI MD-4-9, “Fatigue Screening and Life Assessment of Plain Dents and Dents Interacting with Welds and Metal Loss,” Prepared for the Pipeline Research Council International, Inc., 2018. Catlog No. PR- 214-114500-R01
[5] “Low Frequency ERW and Lap Welded Longitudinal Seam Evaluation,” TTO Number 5, Integrity Management Program Delivery Order DTRS56- 02-D-70036. Michael Baker Jr. inc., Kiefner and Associates, Inc., CorrMET Engineering Services, PC. April, 2004
[6] BMT Fleet Technology, “Fatigue Considerations for Natural Gas Transmission Pipelines”, Report. Prepared for Interstate Natural Gas Association of America (INGAA)
[7] Canadian Energy Pipeline Association, “Management of Shallow Retrained Dents”, CEPA Report. prepared by BMT, 2018.
[8] Dotson,R, Ginten,M, Alexander,C, Bedoya,J, Schroeer,K, “ Combining High Resolution In-Line Geometry Tools and Finite Element Analysis to Improve Dent Assessments”, Paper No. PPIMILI2-16, Pipeline Pigging & Integrity Management Conference, Houston, Texas, February 10-13, 2014.
[9] Bood, R, Gali, M, Marewski, U, Steiner, M, Zarea, M, “EPRG Methods for Assessing the Tolerance of and Resistance of Pipelines to External Damage (Parts 1 + 2)”, European Pipeline Research Group (EPRG), 10-11/1999 Pg 739-744, 12/1999 Pg 806- 811.
Original Work