Optimisation of Underwater Inspection Programmes

Abstract

Underwater inspection of offshore oil and gas structures in the North Sea has evolved over the last 20 years. The initial techniques were fairly primitive by comparison with current methods.

This paper examines the development of underwater inspection in the North Sea from the late 1960’s to the present day and considers how programmes can be rationalised. It looks at both techniques used and training given. Current inspection methods are reviewed with particular emphasis on steel structures.

There is generally greater opportunity to optimise inspection costs on steel structures, be they floating or fixed. Concrete gravity platforms are discussed but by their very nature the inspection requirements for concrete are less onerous.

The key to optimisation of underwater inspection programmes begins at the conceptual or design phase of a new platform. Input by qualified engineers can significantly reduce inspection and maintenance costs downstream.

Substantial financial savings can also be made by reviewing and rationalising inspection programmes during the service life of offshore structures. Quest Consulting Ltd. has extensive experience in this area and its staff have worked in this capacity for a number of North Sea Operators over the past ten years.

It is important that with any inspection programme, the reason for inspection is clearly defined. This should be to ensure the continuing ‘fitness for purpose’ of the structure by most the cost effective methods. To achieve this, the engineer must have sympathy and an understanding for the loads and possible degradation of the structure.

This paper concludes with some of the methods available and details the data required to fully optimise an underwater inspection programme.