Mechanical Interference fit connection (MIFC) has been considered one of alternative solution in joining method for pipeline application. It has been applied mostly for onshore pipeline application. Offshore application of this pipeline connection are considered limited. This joining method offer benefit of faster joining rate, in which for offshore application, it will be the major cost element for installation. However there are more loading condition that need to be mitigated for offshore pipeline compared to onshore pipeline.
There are significant difference between welding and this MIFC in term of quality assurance (QA) and quality control (QC) that can be applied, especially for site acceptance criteria. Therefore there was a requirement to demonstrate the design and integrity of the MIFC to meet the conventional requirement for pipeline welding as part of the regulatory requirement for a permit to install (PTI) and permit to operate (PTO).
This paper presents case study in mitigating challenges during qualification and application of the MIFC as first offshore pipeline application in Malaysia. In this paper, the approach to qualify the performance of the MIFC joint will be described. it includes design verification using finite element analysis (FEA) as well as validation by full-scale testing. Numerous load cases from joint preparation until the pipeline laid on seabed and subsequently during operation stage will be covered for this qualification. Several challenges and mitigation during the qualification and offshore application will also be presented.
The qualification result shows that the MIFC can meet the minimum requirement and some criteria even exceed the requirement of welding. Subsequently, the joint acceptance criteria envelope has also been developed as acceptance criteria for site joining process. This joining criteria has then been proposed for regulatory purposes for offshore application quality assurance and quality control, in-lieu of the acceptance criteria by welding.