Chemical gel cleaning prior to MFL inline inspection of a natural gas transmission pipeline

摘要

Magnetic-flux leakage (MFL) is an accepted and reliable technology for in-line inspection (ILI) of carbon steelnpipelines. When an inspection tool is run under the parameters specified by the vendor, it is able to provide robust andnreliable detection and sizing of metal loss features. Each year, TransCanada (the operator) performs multiple MFL ILIsnon sweet, dry natural gas transmission pipelines throughout North America. In the vast majority of cases, inspectionsnare successfully completed on the first run, largely as a result of extensive preparation on the part of both the pipelinenoperator and the tool vendor. Unfortunately, preparation does not in itself ensure a successful inspection, and factorsnoutside the direct control of the pipeline operator and the tool vendor may interfere with what would otherwise bena successful inspection. This article examines a unique case where the MFL re-inspection of a NPS 30 natural gasntransmission line produced significantly degraded data as a result of debris-induced sensor lift-off. A specialisedngel cleaning programme was required to remove the problematic debris from the pipeline prior to re-running theninspection tool.