Experiences From Welding and AUT of the 15” Norne Clad Pipeline Installed With the Reeling Method

The Norne Satellite project (Statoil) in the Norwegian Sea involves a 9 km long 15” insulated clad steel production pipeline. The line pipe is longitudinally welded SAWL joints of 12m length, with 21mm backing steel (X60) and 3mm metallurgically bonded 316L CRA internally. To prevent waxing of Hydrocarbons during shut downs, use of chemicals has been used to a large extent in this industry. Norne has another philosophy to avoid waxing as the pipeline was installed with a power cable strapped to the coating in a piggy-back solution. This is the “Direct Electrical Heating” solution Statoil has implemented to their pipelines with great success in other projects. The pipeline was installed with the reel ship “CSO Apache” in 2005. It is the first time that a cladded pipeline has been installed with the reeling method. This paper presents experiences from fabrication of the clad steel pipeline. The production welding was performed with a combination of manual and mechanized welding to maintain the CRA integrity and at the same time have an acceptable production rate. The subsequent NDT method was performed by automatic UT (AUT). AUT on cladded pipelines has never been used before and was introduced after a comprehensive study to find a reliable way of detecting and sizing defects in welds with a combination of Austenitic and Ferritic structures.