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REVIEW OF 'UNDERWATER INSPECTION OF STEEL OFFSHORE INSTALLATIONS: IMPLEMENTATION OF A NEW APPROACH'by Marine Technology Directorate (MTD 89/104) 1989 |
This report was produced in 1989 from a joint industry funded project, involving a wide range of participants (24 in total).. It includes a review of underwater inspection requirements, techniques available, significance of defects and different approaches to planning inspections, leading to the development of a revised approach to inspection which is outlined in the report. Although the report was produced over 10 years ago, it is still useful, as it contains valuable background material and in several areas there has been little further development over that timescale.
In terms of structural monitoring there are three significant sections in the report which are:
i) Outline of Structural Monitoring (section 7.1.4)
This details the role of monitoring, in relation to NDE inspection, for maintaining structural integrity. The sensitivity of the process is discussed, together with planned coverage of a platform, and how the technique might be used in practice (continuous or occasional use).
ii) Monitoring methods (section 7.5)
This section, consisting of six pages, covers vibration monitoring methods, acoustic emission methods, fibre-optic crack monitoring, performance based monitoring, crack propagation and flooded member monitoring. In addition the components of monitoring systems are reviewed, e.g. data acquisition, transmission and processing. Examples are given of the mode shapes expected from vibration monitoring, together with expected accuracies of measuring frequency changes (1% for frequencies, 10% for deformed shapes). A table is also provided of results from monitoring a North Sea platform with a severed member, showing both the predicted and measured frequency changes, with generally good agreement between these.
iii) Design and Fabrication to incorporate Structural Monitoring (section 10.3.3)
This short section outlines the requirements to fit equipment for monitoring during fabrication. The techniques addressed include vibration analysis, flexibility monitoring, acoustic emission and strain & foundation monitoring.