Multi-beam echo sounder first on Interconnector pipeline
23 Jul 2007
MBES devices operate by sending out a fan of narrow acoustic beams from a fixed unit aboard a vessel. These beams “echo” back data which generates a detailed 3D image of the terrain including, in this case, the pipeline.
According to Lloyds, the technique provides a higher quality survey at a lower cost compared to conventional methods and avoids the practical and safety hazards associated with deploying equipment over the side in adverse sea conditions.
A specialised Polish research vessel RV IMOR, was used for the 190km-length survey carried out for Interconnector (UK) Ltd on their gas pipeline linking Belgium and the UK.
The Reson Seabat MBES unit used in the survey - around which the IMOR was designed and constructed - gives up to 30 pulses per second from 101 transducers to yield depths to an accuracy of about 1cm. A complete set of data is obtained by combining DGPS positioning with correction for vessel movement in three axes.
Multi-beam echo sound surveys provide us with excellent data for managing the integrity of subsea pipelines, according to John Thornton, Lloyd’s Register Project Manager for the Interconnector contract.
“The technique is commonly used for limited, specialised work but this is the first time it has been used as part of a routine offshore pipeline survey as far as we and Caledonian Geotech Ltd are aware,” said Thornton. “The IMOR proved to be an ideal workboat for this pipeline and everyone involved worked extremely hard to make this first survey in the North Sea a success.”
Lloyds’ work on the project was carried out in conjunction with Caledonian Geotech Ltd and the Maritime Institute in Gdansk. Interconnector UK operates a sub-sea pipeline and terminal facilities connecting Bacton in Norfolk and Zeebrugge in Belgium. It can transport up to 23.5 billion cubic metres/year from Zeebrugge to Bacton and 20 bcm/yr in the opposite direction.
