Interconnector UK Limited - Fatigue life assessment of pipeline

Piperline-inspection and maintenance - Interconnector Terminal - 306x172Regular pipeline inspections and maintenance optimise efficiency and availability for strategic energy link

Client: Interconnector UK Limited
Asset type: Subsea pipeline and onshore terminals
Location: UK, Belgium and North Sea
Project scope: Integrity engineering fatigue life assessment of pipeline span

About Interconnector UK Limited

The Interconnector pipeline - which stretches 235 km, is over a metre in diameter and operates at pressures up to 147 bar - provides a strategic energy link between the UK and continental Europe. The pipeline runs beneath the southern North Sea, connecting Bacton in the UK with Zeebrugge in Belgium.

Business challenge

The Interconnector pipeline transports up to 1/3 of the UK’s gas supply to and from mainland Europe, an incident resulting in an unplanned shutdown would have serious implications for gas supply to UK and Europe for both industry and domestic users.

Following a routine subsea survey, Lloyd's Register Energy identified a free span on a pipeline (where the seabed sediments have been eroded, or scoured away and the pipeline is no longer supported on the seabed) exceeding its operational allowable limit.

For such a length of span, it was deemed likely that the pipeline would vibrate and consequently, there was risk of fatigue failure. This prompted Interconnector to request a more in-depth assessment of the pipeline which would determine the suitability and risks associated with continuing to use the pipeline as-is.

How Lloyd’s Register helped 

Lloyd’s Register Energy was contracted to provide its expertise in engineering consultancy and integrity engineering. Our assessment involved gathering data on design parameters of the pipeline and reviewing them against the current conditions of span length against factors such as current flow, applying our subsea pipeline knowledge and analysis experience.

The detailed fatigue assessment determined that the fatigue life of the span exceeded the remaining design life of the pipeline, when considering operating conditions and the subsea environment.  The seabed at the span location was also very dynamic which could feasibly help in rectifying the span. Therefore, the recommendations were to re-survey the span in two years to assess condition at that time.

Results:

Based upon the outcome of the analysis and assessment of the risks to health, environment, business and reputation it was determined that the pipeline could continue to operate under the current conditions. 

Interconnector was advised to re-survey the span within two years to re-assess its condition.

The findings and recommendations made eliminated the need for any other action such as expensive vessel and equipment hire required to rectify the span.

Benefits:

  • Confidence in the integrity of the pipeline.
  • Evidence to show HSE and DECC that the issue has been resolved.
  • Cost saving due to elimination of unnecessary resolution

Interconnect UK Limited testimonial:

“The continued confidence in the integrity of our pipeline is a key component of our business risk profile.

The work carried out by Lloyd's Register Energy provided the required assurance that the integrity of the pipeline was not compromised, it also gave assurance to the Company and other stakeholders that the design life of the pipeline was not adversely affected. In addition, this work saved the time and expense of un-necessary remedial works.”

Roy Crowther, Project Manager, Interconnector