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The Hydra-Lok® repair installs a steel reinforcing liner, made from compatible material, inside the caisson to bridge the corrosion damage. After installation, the liner transfers axial and bending loads across the weakened section, allowing the caisson to be returned to service immediately. The liner is swaged against the inside of the caisson using proven Hydra-Lok® technology. The Hydra-Lok® swaging system has been used to make hundreds of structural connections on subsea templates and platform jackets around the world since 1984. The liner is fabricated to a length determined after the cleaned caisson has been ultrasonically surveyed for thickness. The liner diameter is controlled such that it occupies minimal annular space. This permits the pump to be returned to its original location in the caisson. |
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Reinforcing a corroded section |
Extending a
broken caisson |
Replacing a missing section | |
Two swaged connections are made, one above and one below the corrosion-damaged zone (see Swaging Process left). Each connection is made when water pressure, captured between the Hydra-Lok® tool's high-pressure seals, expands a section of the liner outward against the caisson. The swaging process, which takes only about 30 minutes, is accurately monitored and controlled in real time by measuring and plotting pressure against the volume of water pumped.
The Hydra-Lok® swaged-liner method can also be used to replace caisson sections lost as a result of corrosion (see illustrations above).
The Hydra-Lok® swaging operation is conducted from the cellar deck of the platform itself. No diver or ROV support is required, because the Hydra-Lok® tool, which applies the necessary hydraulic pressure to swage the liner, is remotely operated, and no equipment is deployed external to the caisson. The repair can be scheduled to the convenience of the platform operator and can be completed in all but the most severe weather conditions.
The Hydra-Lok® method is simple and straightforward and does not disrupt other operations on the platform. Only the liner, the Hydra-Lok® tool, and a compact control/power unit are mobilized to the platform. The crane normally used for pump removal, a water supply (15-litres/minute), and an air supply (7 bar @ 4 m3/minute) are the only on-site requirements for liner installation. The crew comprises two Oil States MCS technicians.
Hydra-Lok® tools are available for standard caisson sizes from 12 inches OD and larger, and liner fabrication is straightforward, so the lead time for a repair is typically 4 weeks or less. Custom tools can be designed and built for special applications. | |
Oil States Industries, Inc.
Oil States International, Inc.