The scope

A major operator had identified the need to continue operation of an 18” condensate pipeline in the North Sea beyond its design life. The operator requested our team to conduct a lifetime extension (LTE) assessment to determine requirements for extending the design life of the pipeline.

The solution

We completed an assessment of the permissible extension to operating life, utilising the methodology defined in NORSOK ISO/TS 12747 and Y-002. Our team progressed the assessment through the following stages:

1. Determination of the LTE requirements
2. Assessment of the current integrity of the pipeline system and a review of the operational history, including any changes to the original system design premise
3. Identification of the threats to the pipeline system during extended life
4. Assessment of any identified threats to the pipeline during the extended operating period, determining the need for any mitigation and remediation measures
5. Implementation of the LTE and specification of inspection and monitoring requirements to ensure fitness-for-service of the pipeline during future operation

During performance of the assessment, it became clear that the factor governing remnant life of the system was the potential for internal corrosion at the base of the inlet riser. Whilst inline inspection data was available for the majority of the system, quality of data in this region was compromised. To solve this issue, we performed a structural reliability assessment (SRA), utilising the remainder of inspection data to determine the acceptable remnant life.

The benefits

From this assessment and recommendations, our client was given confidence that the pipeline was suitable for continued and safe operation over the coming years. In addition, they were clear on the actions required to manage integrity during the extended operating period and how to further increase the operating life if required. We have provided continued support to our client to ensure that the pipeline continues to operate safely and economically.

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