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Integrity of primary structure of fixed steel installations


Prior to 1988, installations were subject to the requirements of obtaining a five-yearly certificate of fitness (CoF). The role of assessing the fitness-for-purpose of offshore installations for continuing operations rested with the certifying authority, which was appointed by the regulator. This role consisted of assessing inspection techniques and results, and overseeing repairs and technical reassessment as needs arose, subject to technical guidance (‘the 4th Edition’) and survey requirements laid down in statute, to qualify for a CoF.

The age of fixed steel installations operating in the North Sea is variable. Over 250 fixed steel installations have been constructed and installed during a period of 40 years to the prevailing standard at that time. In 1998, the certification regime was replaced by a risk-based regulatory regime. This entails the inspection and assessment requirements being subject to the duty holder’s own technical planning with an element of independent verification by a third party.  The results of such arrangements are not required to be automatically reported to the regulator. Many installations are now operating, or seeking to operate, beyond their original design life. Degradation due to fatigue and corrosion and accidental abuse of the structure may have accumulated, leading to a degradation of the structural integrity of the installation. Older assets have changed hands to organisations with less North Sea experience and less in-house technical resources for the management of structural integrity.

Evidence of the overall integrity of North Sea fixed installations is not available to the regulator other than assurance given by the post-1998 system. The reporting of damage / deterioration is subject to the ‘imminent danger’ provisions of the Offshore Installations and Wells (Design and Construction, etc.) Regulations 1996 (DCR). However, this is inadequate in the event of anything other than catastrophic structural failure.

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Issues addressed from safety case assessment


Scope and plan

The underwater integrity programme is intended to cover duty holders’ management framework, covering aspects such as organisational arrangements, technical planning, underwater inspection, technical standards and competencies, assessment of results and acting on results. The elements of such a framework are summarised in Annex 2.

Activity has already been carried out on some installations which will contribute to the planning phase of the project. Discussion has to take place with some industry representatives and the independent competent persons (ICP) in order to discuss current practice. Earlier intervention activity was documented in a report in 1996.

The work will be performed primarily by specialist inspectors in agreement with their nominated inspection management teams via the inspection planning process. It is expected that the following will be carried out:

Limited support will be required from inspection management teams (IMT) to facilitate the work. It is envisaged that efforts will be made to co-ordinate where possible with the post acceptance inspection topic (PAIT) inspection activities required by OSD.


Inspection reports will be produced for each intervention. Feedback will be given on individual installations.

Supporting information

Research and technical support needs

Some technical support (under the Framework Agreement) is being initiated and further work may be required in response to any issues that arise. See the research and development page for further information.


Annex 1 - ISO 19902 overview

Annex 2 - Underwater integrity management framework

Annex 3 - Fixed steel installation underwater integrity management template

Updated 2012-12-13