Jul 2013
Gas Transmission
Evaluation of Inspection Techniques for Sleeved Crossings
Jul 2013
Mar 2014
National Grid Gas Transmission
Robert Stockley, box.GT.innovation@nationalgrid.com
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Network Innovation Allowance
During a routine Inline Inspection (ILI) operation, a 16% metal loss feature was detected within a 40 metre long sleeved road crossing. In addition to the 16% metal loss feature, the inline inspection (ILI) also confirmed that the pipe section within the sleeve contains other metal loss features. An inspected was undertaken six years previously with no evidence of metal loss features in the pipe section located within the sleeved crossing.

Other than the Inline Inspection (ILI) technique, no other reliable technologies are currently available to inspect defects contained within sleeved sections of pipeline. This can lead to risk associated with accurately determining the period in which corrosion started to develop between Inline Inspections, and therefore the corrosion rate.

The suitability of alternative pipeline inspection systems, such as ultrasonic guided wave inspection system, for use as a complement to the Inline Inspection (ILI) technique is not fully understand at this time. Information gained from this study will provide a better understanding of the process involved with the inspection of pipeline areas where metal loss has been found during a standard Inline Inspection, currently scheduled at approximately 10-14 year intervals.

The key objective is to evaluate a number of guided wave ultrasonic inspection techniques for their suitability in use on above ground inspection of sleeved pipe sections.

Information gathered on the guided wave ultrasonic systems trialed during this project will allow for an informed evaluation on the use of a non-invasive above ground inspection techniques on sleeved crossings as a complement to Inline Inspections (ILI’s); following a review and update of relevant policy.