Page 173 - Pipeline Pigging Technology

Pipeline Pigging Technology

Fig.7. Pipewall thickness statistics - operation 1.

In addition to these pipe-wall thickness statistics, a general assessment of
girth weld condition was given in the form of a simple grading system, which
identified uncorroded welds, corrosion less than 10% depth, and corrosion
greater than 10% depth.
In addition to this overall view of the pipeline condition, separate standard
feature reports were prepared for the deepest individual corrosion pits found
in the line. An example of this report is shown in Fig.8. For each pit the depth,
width and length were given, together with location details.
From the very first inspection operation, discussion took place between
BP and British Gas in an attempt to fully evaluate the vast quantity of
information produced and its relevance to the operation of the pipeline. BP
entered, at this time, into a separate contract with the British Gas Engineering
Research Station to provide a consultancy service on the fracture mechanics'
assessment of the data to determine the significance of the defects.

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