Longterm Partnership in Inline-Inspection (ILI) Services - Experiences, Benefits, Results

Proceedings Publication Date:

10 Jan 2019
Jürgen Ehrhardt
Thomas Hüwener, Frank Kutsch, Jochen Ahlers, Jürgen Ehrhardt
Part of the proceedings of
E.ON Ruhrgas AG (ER) operates the largest high pressure gas pipeline grid in Germany totalling in about 13.000 km of gas transmission lines. In 1996 ER launched an ILI program which was initially scheduled until 2020. The motivation for the ILI work was to preserve safe operation and integrity of the assets and to achieve potential savings by improved documentation (electronic logs), precise location of pipeline features by GPS coordinates (less digging work), feature verification by other NDT technologies (more efficient and effective rehabilitation measures), cost optimised planning of rehabilitation measures, documentation for pressure uprating. Despite cathodic protection measures wall thickness reductions and metal loss could occur in the pipelines besides other anomalies. Thus, ER decided to accelerate the ILI program and signed in 2004 a Longterm Service Agreement (LTSA) for 5 years with GE Oil & Gas to execute the ILI scope. The intention for signing an LTSA was to avoid annual contract negotiations, having a call-out structure enabling to concentrate on lines with identical size (cost reduction) and to achieve a significant price reduction due to larger ILI volume. The LTSA scope included infield transport, cleaning, calipper runs (only passage proving) and MFL-IMU inspections. Over the 5 years contract period 53 sections ranging from 20”–48” (incl. dual- and multi-diameter sizes) have been inspected totalling in 4.161 km. The overall number of runs (cleaning, calipper, MFL) was 212 totalling in 17.200 km.

Based on results and experience during the contract period ER ordered additional services such as full calipper reports, RunCom studies, an FFP study and Strain Assessment studies.

Throughout the project execution both parties improved the cooperation and performance operationally and economically by implementing of lessons learned. Key points were: firm assignment and keeping continuity of key personnel, implementation of quarterly management meetings, implementation of customer communication platform, open communication both way, full feedback and support from ER helping to improve data analysis and testing new techniques, improving and customizing report structure fitting into ER’s PIMS system.

And the most important highlight over 5 years work. Lost Time Injury Frequency (LTIF) was zero over the contract period meaning the safety of employees was of top priority for both contract partners.