RISPECT Public Website

Date: 19th November, 2008

Structural failures of ships are, relative to onshore structures, very common and these contribute to the personal risk levels of mariners, and high pollution and economic costs.
Ships operate in a severely corroding and (metal) fatiguing environment that reduces the strength of the ship structure which can only be kept safe by regular inspection and repair of paint coatings, excessively corroded plate and fatigue cracks.
Present inspection planning, and feedback to design, is based on long term experience with usually no account taken of the needs of any specific ship. Reliability or Risk-based methods, applied in other industries, are not applicable to this problem of using information from large numbers of ships to improve the inspection planning of any given ship.
This project's methodology has evolved partly from a recognition that integrating two apparently different methods for inspection planning should allow better decisions to be made:

1) Inspection, timing, method and feedback to design for ships has traditionally been based on experience and is essentially determined by class rules and allows them to be improved. The resulting inspection programs are usually the same for all types of ships. Exceptionally, if severe problems are found, more inspection may be demanded by the classification society for the particular ship and any sister ships. The traditional method has the advantage that it is based on an overview of ship related structural problems but cannot deal well with ship to ship variations in construction or use.

2) Very occasionally, first principles, reliability based, methods have also been used to determine ship reliability and the required inspection levels and even more rarely, the initial design requirements. These methods have generally been applied to individual component parts of individual ships and can deal reasonably well with the individual part but they do not give a good estimate of the overall reliability of the ship and, crucially, they lack the large personal awareness "experience database" that the traditional, experience-based, methodology uses, so the reliability methods are not calibrated by reality.

This project will bring the two methods together and will develop and demonstrate an improved decision making method, based on a combination of experience-based and first-principles, statistical analysis, for safe, cost-effective structural inspection, repair and design rule improvement of existing ships. Within the proposed primary methodology the experience base will be handled statistically but, in parallel, the classification society experience will also be tapped, using an expert system approach, to try and provide a 'common-sense' check on the purely statistical analysis and warn users of possible shortcomings in the method's predictions.
This will lead to improved justification of important decisions, better inspections, more important defects being found and repaired, better initial design, fewer pollution incidents and the saving of lives.
In addition the project will provide better interfaces between ship manager, owner, class, regulatory authority and repair yard in order to improve the efficiency of structural data management and (selective) distribution.

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19th Nov 2008 PROJECT SUMMARY