About the project

Floating platforms for plant, machinery and accommodation are being used increasingly in offshore oil and gas production. Semi-submersible drilling rigs have for some time been common in offshore exploration, but now floating structures are to be found in 'Tension Leg' platforms, 'Spar' platforms, 'Floating Production Storage and Off-loading vessels' and support structures such as 'Flotels' (accommodation) and crane barges. As oil fields are opened up in deep water at the margins of the continental shelf, production platforms that are fixed to the sea bed are no longer feasible, moreover floating production platforms can be moved from one field to the next, allowing smaller, marginal fields to be exploited.

Permanent floating production platforms must be moored to the sea bed. The integrity of the mooring system is critical, because the consequences of failure could be oil pollution on a catastrophic scale. The rupture of a well head off the coast of Mexico in 1985 released 64 million barrels of oil (compared with 200,000 barrels of oil from the Exxon Valdez). Floating structures are designed, in common with all offshore structures, to survive the 15m waves derived statistically from the '100 year storm'. However there is evidence of much greater freak waves, for example the 26m wave which hit the Draupner platform in the N Sea in 1995. Also, climate change suggests that storms will become more frequent in the future increasing the risk of damage to offshore structures. Recorded instances of damage to the mooring system of floating offshore structures already indicate a problem. Current cable chain breaks are as high as one break for every 3 years of operation. Breaks often go unnoticed, increasing the probability of multiple breaks and total mooring system failure.

There is therefore an urgent need to improve the integrity management of mooring systems. One issue is the inspection of chain links. Regulatory visual inspection is currently done with the cable chain brought up on deck, or, for greater sensitivity to defects using non-destructive tests (NDT), with the cable chain taken on-shore. Increasingly, interim 'swim-by' inspections of the chain in-situ are being conducted from Remote Operated Vehicles. The inspection however is unreliable, susceptible to human error, because of the hundreds of metres of chain involved and the short times allowed for inspection. Industry recognises the need for more effective inspection.

The inspection system proposed here in the EC project ChainTest will be applicable to stud-less chains in situ, below water. It will be automated and will be sensitive to fatigue cracks, corrosion and bent chains.

CHAINTEST is a collaboration between the following organisations: TWI Ltd, Miltech Hellas SA, Technical Software Consultants Ltd, Bytest srl, Interlab Ingenieria Electronica y de Control, S.A., Nuclear Engineering Services Ltd, Vicinay Cadenas SA, Petroleo Brasileiro SA, Zenon SA - Robotics and Informatics, and NDT Consultants Ltd. The project is co-ordinated and managed by TWI Ltd. and is partly funded by the EC under the CRAFT programme ref number: COOP-CT-2005-018236 CHAINTEST.



About the project Floating platforms for plant, machinery and accommodation are being used increasingly in offshore oil and gas production. Semi-submersible drilling rigs have for some time been common in offshore exploration, but now floating structures are to be found in 'Tension Leg' platforms, 'Spar' platforms, 'Floating Production Storage and Off-loading vessels' and support structures such as 'Flotels' (accommodation) and crane barges. As oil fields are opened up in deep water at the margins of the continental shelf, production platforms that are fixed to the sea bed are no longer feasible, moreover floating production platforms can be moved from one field to the next, allowing smaller, marginal fields to be exploited. Permanent floating production platforms must be moored to the sea bed. The integrity of the mooring system is critical, because the consequences of failure could be oil pollution on a catastrophic scale. The rupture of a well head off the coast of Mexico in 1985 released 64 million barrels of oil (compared with 200,000 barrels of oil from the Exxon Valdez). Floating structures are designed, in common with all offshore structures, to survive the 15m waves derived statistically from the '100 year storm'. However there is evidence of much greater freak waves, for example the 26m wave which hit the Draupner platform in the N Sea in 1995. Also, climate change suggests that storms will become more frequent in the future increasing the risk of damage to offshore structures. Recorded instances of damage to the mooring system of floating offshore structures already indicate a problem. Current cable chain breaks are as high as one break for every 3 years of operation. Breaks often go unnoticed, increasing the probability of multiple breaks and total mooring system failure. There is therefore an urgent need to improve the integrity management of mooring systems. One issue is the inspection of chain links. Regulatory visual inspection is currently done with the cable chain brought up on deck, or, for greater sensitivity to defects using non-destructive tests (NDT), with the cable chain taken on-shore. Increasingly, interim 'swim-by' inspections of the chain in-situ are being conducted from Remote Operated Vehicles. The inspection however is unreliable, susceptible to human error, because of the hundreds of metres of chain involved and the short times allowed for inspection. Industry recognises the need for more effective inspection. The inspection system proposed here in the EC project ChainTest will be applicable to stud-less chains in situ, below water. It will be automated and will be sensitive to fatigue cracks, corrosion and bent chains. CHAINTEST is a collaboration between the following organisations: TWI Ltd, Miltech Hellas SA, Technical Software Consultants Ltd, Bytest srl, Interlab Ingenieria Electronica y de Control, S.A., Nuclear Engineering Services Ltd, Vicinay Cadenas SA, Petroleo Brasileiro SA, Zenon SA - Robotics and Informatics, and NDT Consultants Ltd. The project is co-ordinated and managed by TWI Ltd. and is partly funded by the EC under the CRAFT programme ref number: COOP-CT-2005-018236 CHAINTEST.

THE SIXTH FRAMEWORK PROGRAMME	European Commission