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FP6

OPCOM Report Summary

Project ID: 516993
Funded under: FP6-NMP
Country: United Kingdom

Final Report Summary - OPCOM (Development of Ultrasonic Guided Wave Inspection Technology for the Condition Monitoring of Offshore Structures)

The objective of the OPCOM project was to design and build a prototype system, using Ultrasonic Guided Wave (UGW) Technology to continuously monitor the integrity of offshore structures such as oil production platforms and wind turbine towers.

The main project results in this report include:
- The determination of the issues of relevance to the operators of offshore wind farms and oil and gas production facilities.
- The development of techniques for examination of offshore wind turbine and oil production structures.
- Development and production of the prototype equipment.
- Results of the field tests carried out.
- The dissemination activities.

The scientific and technical objectives were:
- To develop Ultrasonic Guided Wave (UGW) technology as a qualitative and quantitative tool for detection of fatigue cracks and corrosion/defects in tubular members.
- To develop permanently mounted marinised UGW Sensors and Systems that can be deployed and fixed permanently onto the tubular members of offshore structures.
- To develop UGW sensors and systems that will remain permanently in place for decades needing only occasional maintenance.
- To develop the above techniques with automated defect recognition capabilities so that the operator subjectivity that is present in all current NDT techniques is eliminated.

The economic objectives were:
- A significant reduction in the cost of underwater inspection of tubular support structures due to the elimination of the need for removal of marine growth and the removal and reinstatement of coatings and elimination of the use of divers.
- A reduction in the number of spillages caused by leaks from offshore oil and gas platforms due to cracking and corrosion and subsequent product losses and clean-up costs.
- A reduction in inspection time and thus reduction in loss of production during inspection.

The social objectives were:
- Elimination of hazard due to diving accidents while inspecting offshore structures.
- Elimination of labour intensive and monotonous underwater inspection tasks.
- Reduction in operator stress and error caused by the need for great attention to detail and NDT process variability.
- Reduction in exposure of contract workers to danger.

The environmental objectives were:
- Elimination/reduction of spillages of hazardous fluids from offshore oil and gas platforms and contamination of seas and pollution of natural habitats.
- The project would also encourage the use of renewable wind power by developing safe methods of wind turbine tower inspection.

The objectives of the first work package were the following:
- To determine needs of end users in offshore oil production and wind energy and of safety authorities.
- To provide essential input parameters, including inspection objectives, range of tube diameters and wall thicknesses and discontinuities for development of test techniques.
- To design mock-ups for parametric studies in the laboratory.
- To procure structures for field trials offshore and in a diver training tank.

The objectives of the second work package were the following:
- To determine the essential procedure parameters influenced by the given input parameters.
- To investigate, both with numerical models and experimentally, the propagation of guided waves through tubular frames above and below water.
- To investigate, both with numerical models and experimentally, the propagation of guided waves along large diameter, thick-walled cylinders above and below water.
- To investigate the interaction of guided waves with cracks, corrosion and flooded members.
- To determine the environmental parameters that will affect system performance throughout its life-cycle.

Both modelling and experimental techniques were used to determine appropriate conditions for examination of the selected components. These were backed up by controlled field tests to establish the applicability of the equipment and procedures developed.

The apparatus that was used was of two kinds: a ruggedised version of the curved linear array and a marinised device suitable for deployment on oil and gas installations either in the splash zone or sub-sea. The linear array, designed by partner Zenon, was developed specifically to be attached to the top edge of the large tubular piles used as the foundation of the offshore wind turbines.

For the oil and gas applications, a combined tool was designed, in which an encircling collar could be placed around the tubular components to be tested to attach the test transducers, with the controlling electronics in an integrated watertight compartment.

A key element of this project was to demonstrate the performance of the test system offshore. Tests were carried out on the Statoil Hydro Sleipner B production platform in the Norwegian sector of the North Sea.

The components tested were two large tubular caissons which were part of the fire water supply system for the platform. Each was 660 mm in diameter, 17.48 mm thick and approximately 63m long. These were selected for study as they were both known to contain corrosion, which allowed the capability of the system to detect this damage to be assessed. The top of each caisson was a flange at the underside of the main platform deck, where it was bolted to the platform pipework. The tubulars ran vertically downwards into the sea and were supported by guide brackets at the spider deck level.

Related information

Contact

Peter MUDGE, (Consultant)
Tel.: +44-1223891162
Fax: +44-1223892588
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