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Structural topside inspection and fabric condition

Background

Fixed structures are essentially passive systems with much reliance being placed on their initial integrity. They are normally inspected visually on an annual frequency by a visiting team, with very little maintenance being undertaken. More attention is given to underwater structures during inspection activity, due to access difficulties, the corrosive environment and wave loading leading to fatigue. However, failure of the topside structures would be equally catastrophic directly impacting on operational serviceability requirements

Fabric condition is an all encompassing term, used to describe the state of various secondary structures, and some larger items of plant and equipment supports. Although, some of these items may not be safety critical elements, their failure could lead to personal injuries or initiating progressive events onto other items. These components should normally be covered by the ongoing planned maintenance (PM) scheme, and there is evidence that this work has been deferred on some installations where sale or abandonment is considered likely.

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Issues addressed

Some evidence from inspections has suggested that there may be items that are not being covered properly by either the topsides structural inspection or the PM scheme.

Intended outcome

The main intended outcomes are as follows:

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Plan and timescales

It is planned that onshore and offshore inspections will be carried out. The focus would be on older fixed production platforms in the first instance, as experience to date suggests that this is the area where problems are more likely.

Two question sets (Appendices 1 and 2) have been developed for topside structural inspection and for management of fabric condition, in view of the likely different management arrangements for the two activities. A key aspect will be to examine the interfaces between these arrangements to identify gaps or overlaps.

It should be noted that some aspects of fabric condition may have been examined during previous inspections or other IMT activity. The structural inspector should check for this, and some reduction in work scope may be appropriate. There are interfaces between this topside proposal and the other SIMIP project on blast wall integrity. However, to cover the whole structure the underwater inspection proposal must also be included, and the possibility of combined visits should be considered during planning.

Deliverables

Inspection reports will be produced for each intervention.

A report will be produced to summarise progress and to assess the impact of the work in a qualitative fashion. This will determine the work needs and format to continue in subsequent years. A short annual report will be prepared for each subsequent year.

A Safety Notice may be prepared to identify particular areas of concern, if necessary.

Paper(s) may be prepared for dissemination to various stakeholders, based on the yearly reports.

Supporting information

Research and Technical support needs

No immediate needs are envisaged. Some technical support (under the Framework Agreement) may be required in response to issues arising or for impact evaluation purposes.

Appendices

Updated 2012-12-13