ECA debuted am AUV capable of performing pipeline and riser inspections in 3,000 m water depth during the Deep Offshore Technology conference in Marseille, France.
The Alistar 3000 combines absolute and relative navigation to allow inspections, said Dominique Mallet, sales engineer at ECA. The company wanted AUVs that were capable of doing more than just recording the underwater scene while governed by absolute navigation, provided by the inertial navigation system, he said. ECA added the ability to navigate relative to an item underwater by applying sonar technology.
With the ability to handle vertical inspection, he said, ECA believes the AUV will be useful for inspection risers, mooring lines, and pipelay. The company simulated the vertical inspection in 13 m of water in the French Mediterranean for potential customers during DOT. The Alistar 300, which performed the demonstration, was pre-programmed to inspect a pipeline in a known location. Mallet said ECA plans to perform deepwater horizontal inspections, suitable for pipelines, for potential customers in December.
The Alistar 3000 requires less infrastructure on a vessel, so a smaller vessel can be used than typically. The units can record video and sonar data while tracking the equipment to be inspected, while recording the information for later analysis. It is 5 m long, 1.45 m high, and 1.68 m wide, and weighs 2,100 kg, excluding 150 kg payload. It can reach 6 knots and can hover on a location. The Alistar 3000 will have the Inertial Navigation System, Kalman Filter, Doppler Velocity Log, a high-accuracy depth sensor, altimeter, and obstacle avoidance sonar. Communication and positioning equipment includes a two-way radio frequency link, GPS/DGPS receiver, acoustic localization transponder, and acoustic moden.
Primary payload sensors include side scan sonar, multibeam echosounder, sub-bottom profiler, camera and searchlight, CTD or sound velocity probe, and a profiler. ECA says it can be used for construction support with pre-lay surveys, touchdown monitoring, and post-lay surveys.
The company is pairing the AUV with a special launcher, which is now being tested in varying sea states. Once the AUV is launched, the unit is piloted by radio from a desk on the vessel, Mallet said.
11/21/03
