Nov 2017
Gas Transmission
EMAT – In-line Coating Disbondment Detection Assessment
Nov 2017
May 2018
National Grid Gas Transmission
Kirsty McDermott;
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Network Innovation Allowance
Gas Transmission Networks

CIPS are carried out to detect coating disbondment on the pipeline but this is only detection is only location not circumferential position. This lack of accurate circumferential information increases any potential maintenance costs as excavations need to be larger to ensure exposure of the reported features.

The majority of National Grid’s pipelines are coal tar coated. Over time, there can be regions of localised coating disbondment which, if not detected by the CIPS techniques, will inhibit the cathodic protection in that region potentially resulting in pipeline corrosion. If this disbondment occurs at the base of the pipe, the situation is exacerbated as CIPS has been shown to not reliably identify disbondment under these conditions. Other pipeline evaluation techniques, such as EMAT, have been show to provide coating condition and adherence information. This technology, when utilised as an in-line Inspection tool, offer considerable potential supporting the pipeline asset integrity assessment that are undertaken by National Grid.

This project will conduct an ILI EMAT trial alongside a scheduled MFL ILI run along the same transmission feeder section. This will provide a direct comparison of the technologies and allowing for verification of the ILI capability of the two methods in terms of:

  • Distribution of coating condition plots: Number of joints per coating condition class for each 5,000m of pipeline length.

  • Coating condition per joint plot: detected coating condition as percentage of joint area affected versus the pipeline length.

  • Coating Type per Joint: Detected main coating type per joint versus the pipeline length

  • Pipe Tally: All results of the inspection activities.

The trial will be the first use of the EMAT ILI vehicle in the UK and verification of it’s suitability offers the potential for improved pipeline asset management through the continued use of the EMAT technology.

To evaluate the effectiveness of ILI EMAT tool to detect coating disbondment.

The success will be measured by full verification, analysis and validation of the data confirming EMAT can detect coating disbondment.