Case Study: Inspection of an oxygen pipeline in Germany using Magnetic Flux Leakage (MFL) during a refinery shutdown
Proceedings Publication Date
Jochen Ahlers
Jochen Ahlers, Dr. Rainer Keienburg, Kristoffer Kotzur
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AIR LIQUIDE Deutschland GmbH (ALD) wished to carry out in-line inspection (ILI) of 8” and 12” oxygen pipeline sections within a 21-day shutdown period. Both sections had never been previously inspected with ILI tools and ALD was willing to conduct the inspection in water or nitrogen. The scope was metal loss inspection, specifically for pinhole defects, along with geometry and mapping.

There were several challenges to overcome with the project. Firstly, there are technical and legal requirements for all equipment used in or near oxygen pipelines, while the Federal Institute for Materials Research and Testing (BAM) Berlin has to approve the compatibility of all non-metallic materials touching the pipe wall. The turnkey project involved four separate companies, so a greater than usual level of project co-ordination was required.

For Baker Hughes, a GE company (BHGE) an inspection in water was ruled out as the extensive drying requirements would not be possible within the given timeframe. Inspection in gaseous nitrogen was considered the only option, although ALD had an unsatisfying experience with an inspection of an oxygen pipeline using nitrogen as propelling medium in 2014. BHGE has nitrogen pumping equipment and experience so both these and the ILI services were available inhouse. BHGE successfully ran its latest generation MagneScan™ ILI tool with the highest level of detection and sizing.

In addition, BHGE mobilized an experienced senior data analyst to site to inform the ALD immediately of any potentially significant features that could affect reinstatement of the pipeline following the shutdown period. Clear advice on the location of these features was provided by BHGE, with excellent correlation between the reported features and the verified results. Following the completion of field work and the submission and verification of the results, it was clear that the correct methodology had been chosen for this inspection.

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