Earlier this year, GRTgaz successfully completed its advanced magnetic flux leakage (MFL) inspection on a 6inch diameter, 39 km pipeline in Normandy, France. Built in 1965, the pipeline is located to the northwest of Paris and is part of GRTgaz’s 32,000 km gas pipeline system in France.

The MFL inspection was completed using the MagneScan in-line inspection system, which allows operators to map pipelines of diameters as small as 6 inches while also inspecting for metal loss and geometry features.

The new MagneScan system deployed by GRTgaz is the first able to inspect pipelines— of varying diameters and sharp bends — for multiple types of features in a single run. The system was developed by GE Oil & Gas’ PII Pipeline Solutions Centre of Excellence for Magnetics in Northumberland, United Kingdom. PII Pipeline Solutions was instrumental in developing the original MFL technology used for oil and gas pipeline inspection in the 1970s when it was under British Gas ownership.

The system records the position of the pipeline features and anomalies such as:

* Dents, ovalities, and bends; * Internal and external pitting and general corrosion on the pipe body; * Metal loss in the vicinity of welds; and, * Metal loss associated with dents and under casings.

The new MagneScan systems are designed to locate and size areas of metal loss of five per cent wall thickness or greater, and — in practice — detect metal loss even smaller.

Technical features of the new MagneScan that are attractive to pipeline operators include its 216 low noise Hall effect sensors that record readings taken on axial, radial and transverse vectors every 2 mm. This new 3D configuration covers 100 per cent of the pipe circumference and optimises defect-sizing accuracy for width, length and depth. The system simultaneously maps the pipeline and checks it for corrosion, using high resolution MFL sensors that deliver high quality data to identify and locate metal loss and is suitable for geographic information systems (GIS) analysis. Mapping data is integrated with inspection information during the run, reducing the amount of post-processing required.

The improved accuracy means less digs for the operators following inspection runs, which convert to significant savings and reduced environmental impact.

While GRTgaz and GE’s PII Pipeline Solutions had originally agreed that the project would consist of a maximum of five runs to gauge, clean, geometric survey, inspect and map the pipeline, GE instead completed the scope of supply in only four runs, running gauge, cleaner ‘profile’ and the new MagneScan.

“We were very pleased with the performance of the new MagneScan system. It allowed us to complete the inspection with a single pass after the initial gauging, cleaning and dummy tool runs had been completed,” said GRTgaz spokesperson Stéphane Ardiet.

“GE was also able to complete the project within our very tight window – between 19 and 30 January 2009 – to minimise the impact on production from our gas storage facility in St Illiers.”

In addition to the tool’s reliable performance allowing the operation to be carried out ahead of schedule, the project maintained strict compliance with the European Union’s ATEX safety requirements, for operations in potentially explosive atmospheres.

“We have delivered to our client the full inspection report within the eight-week timeframe that was agreed upon, and the results from the analysed data have amazed even the most experienced of our staff,” said General Manager of GE Oil & Gas PII Pipe Solutions John Bucci.

“This technology enables pipeline operators to choose the level of analysis of data they wish to review upon completion of inspection, and allows them to come back to GE later with additional requirements for more in-depth analysis leading to remediation plans.”

To aid data analysts in improving characterisation of complex (interactive or axial) corrosion defects, the new technology presents visually powerful data derived from three magnetic fields – transverse, radial, and axial. These data sets are combined to achieve enhanced defect sizing specifications and improved probability of identification.

Since its introduction at the International Pipeline Conference in Calgary in September 2008, the new technology has completed more than 40 inspection runs, covering over 2,500 km of liquid and gas pipelines across three continents.