Subsea dredger trials

Trials of a new subsea dredging system, which is claimed to have a high capacity for small rock removal, have exceeded all expectations in terms of efficiency and performance.

The Predator Subsea Dredger, a new concept in the world market, underwent a number of trials while fitted to the Triton XL26 work class ROV used for training and trials at The Underwater Centre's Loch Linnhe site near Fort William in Scotland. The Predator Subsea Dredger was designed by Subsea Tooling Services (STS), based in Oldmeldrum, Aberdeenshire, a company that offers a diverse range of subsea equipment.

Nine tonnes of 50-60mm rocks were placed on areas of the seabed to recreate a range of terrains typical of the offshore subsea environment to be dredged during the trial. Dredging these rocks was completed in between eight and nine minutes which equates to a rate of one tonne per minute.

Further trials designed to test the integrity of the system, including the dredging of 100-130mm rocks in an attempt to break the machine and to identify any weak spots, highlighted the robustness and strength of the product. A final test of the agitator system, which shoots out jets of water at the suction head end directly onto the seabed which was used to break up the peat lying at the bottom of Loch Linnhe and dredging it at the same time, worked exceptionally well and did not affect the performance of the dredger.

The Predator can be reconfigured for different soils and rocks which still submerged with the use of a second, work class ROV or by using a diver.

STS Business Development Manager Billy Milne said, "The main objective of the trials was to prove that the Predator was as efficient, if not more so, than other dredgers currently on the market.

We wanted to prove the dredger's capabilities to our clients, as well confirm our development tests by filming it in action in conditions close to those in which it will be used in the offshore environment," he said.

"The Underwater Centre is the only facility within the UK that could have undertaken the task of testing and filming the Predator Dredger. The highly skilled ROV team here demonstrated their ability to handle such an operation. From planning the scope of work to operating the ROV with the Predator Dredger and subsequently delivering footage of the trial, The Underwater Centre has provided a service that is invaluable to our company."

Steve Ham, the General Manager of The Underwater Centre, said that trialling new subsea equipment is an important part of what the Centre does. "Companies such as STS are at the forefront of technology development for the oil and gas sector," he said. "In today's market, it's increasingly important that new technologies are developed more quickly, and in a cost effective way and the facilities we have on offer at the Centre help achieve this by providing an alternative to having to test offshore."