Integrity management of non-piggable pipelines up to now remains as an essential challenge for all Operators. For instance in Gazprom, due to diverse causes ILI technology cannot be applied for 47% of 164,7 thousand kilometers of pipelines. In addition, for half of those pipelines to run ILI is not economically reasonable.
These pipelines are primarily branch pipelines, as well as part of transmission pipelines, which were commissioned more than 30 years ago. These assets have significant value, since they deliver gas to industrial consumers and population.
Widely applicable aboveground survey techniques such as DCVG and CIPS alone, targeted at evaluation of pipeline coating integrity and CP effectiveness, do not entirely determine the integrity of non-piggable pipelines. Furthermore, these methods have limitation – they are not intrinsically sensitive to coating disbondment, which is considered as one of the significant threats to integrity.
In the meantime, over the last years Magnetic Tomography Method went through extensive industrial validation. Based on the converse magnetostrictive effect, MTM defines stress characteristics of pipe sections by registering changes in the magnetic field of the pipeline. But MTM results in low accuracy for detecting pipe features with stress level less than 5% of the SMYS (e.g., pitting corrosion).
As an effective instrument for comprehensive integrity assessment of non-piggable pipelines, authors propose to perform combined DCVG/CIPS/??? survey, which allows to evaluate coating and pipe integrity in one-pass and compensate limitations of each method. This paper is based on DCVG/CIPS/MTM survey results of Gazprom pipelines and describes methodological approach to develop an effective pipeline integrity management plans.