Incidents and failure modes linked to bonded flexible pipes and hoses

Incidents in recent years linked to flexible pipes/hoses on the Norwegian Continental Shelf demonstrate a need for state-of-the-art knowledge about bonded flexible pipes and hoses.

On commission from the Petroleum Safety Authority Norway, the company 4Subsea has conducted a study that provides an overview of experiences of incidents and failure modes linked to bonded flexible pipes and hoses.

In its review, 4Subsea concentrated on design, planning, operation, inspection and maintenance and how to ensure there is adequate documentation and to utilise this information in order to operate flexible pipes and hoses in the safest and most reliable manner.

The work covered the following topics:

• Overview of key features in the development of flexible pipes and hoses
• Overview of the most serious incidents
• Relevant degradation mechanisms and failure modes
• The present state of knowledge and potential future risks and uncertainties concerning degradation, ageing and life extension
• Effects of degradation mechanisms on robustness
• Future trends, developments and challenges
• Integrity management (design and operation)
• Inspection and monitoring methodologies
• Initiatives for improvements and knowledge sharing
• Development of standards

Bonded vs unbonded

Flexible pipes used in the petroleum industry are constructed from several layers of steel and polymers to make them impervious and strong.

There are two different principles for the cross-section design of flexible pipes: bonded, in which the layers are bonded together through vulcanisation, and unbonded, where the layers are able to slide relative to each other.

The report is based on experiences from the Norwegian petroleum activities and international experiences. A range of materials technology centres, manufacturers, suppliers and users contributed to the review. 

The aim of the study is to help make state-of-the-art knowledge about flexible pipes/hoses available and to clarify the challenges that the industry must deal with when using flexible pipes and hoses.