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Sea-Axe Developed for Precise Sediment Removal in Shallow and Deep Water

Alex Whyte with the prototype Sea-Axe during development.

Alex Whyte with the prototype Sea-Axe during development.

Alex Whyte has drawn on three decades of experience to design a controlled flow excavator (CFE) that can be precisely controlled in water from a meter and a half (4.9 feet) to 500 meters (1,640 feet) deep. JBS Subsea of Peterhead, Scotland teamed with Whyte to manufacture and market the new Sea-Axe, which had its commissioning in May.

Whyte described the tool as a “non-intrusive non-contact method of excavation, using a hydraulically operated impeller that draws water in through a top intake and discharges a controlled water column that breaks up the bottom material in a suspension to be carried off in the current. Depth and width of excavation are monitored by multibeam systems. The power can be increased for greater depth, or decreased if over-excavating, remotely and immediately through top side operations.”

It can be precisely positioned to remove material around marine structures to augment maintenance dredging in docks and berths, and to clear the way for repair or deconstruction of underwater structures. For work in shallow water, it can be mounted on any vessel equipped with a crane or A-frame. For deep trenching – up to 500 meters – a dynamic positioning (DP) vessel is required. The DP vessel can hold station through satellite positioning, allowing the Sea-Axe to be monitored and controlled by topside controls.

“There have been many lessons learned over the past years with mass flow operations, and Sea-Axe is simply the evolution,” said Whyte, who is director of JBS Subsea. “It has modern technical advancements and a new patented chamber for added stabilization. It is hydraulically driven via a topside hydraulic power unit (HPU) that supplies motive power and infinite controllability to a powerful bidirectional subsea hydraulic motor, with direct drive to a single, inverted, base-mounted impeller. The inverted impeller allows Sea-Axe to operate as shallow as 1.5 meters and as deep as 500 meters,” he explained.

At the final commissioning, Whyte, (holding the sonar cable), Sea-Axe operators and sonar operator, deploy the unit to excavate next to a quay at the port of Peterhead in Scotland.

For deep trenching, “our tool will have a beacon attached, which allows the survey team to superimpose us on the navigation screen, and we can see where the tool is at all times in relation to any cables or pipelines we are trenching, allowing the DP operators to keep the vessel accurately above the target areas,” Whyte said.

The final commissioning this spring included lowering the unit by port crane into the water and moving it along a quay at the Port of Peterhead, Scotland to remove excess mud and siltation to deepen the berth area.

Peterhead is the busiest oil port in Northeast Scotland.

“We believe this tool will be a great asset in the decommissioning arena, as it is quick, safe and competitively priced,” Whyte said. “For removing seabed areas quickly to allow manipulator access for cutting structures below the seabed there is nothing better. Standard pre- and post-trenching, free span correction, and deburial for inspection are just a few of the many tasks suited to Sea-Axe applications,” he said.

The Sea-Axe is eight tons in weight, two meters (6.6 feet) high and two meters in circumference. The unit and ancillary equipment – HPU and spooler with umbilical and control shack – are easily transportable on a standard flatbed tuck, and transferred by a simple lift with certified lifting assemblies supplied as standard.

Whyte’s 30 years in the excavation industry included stints with Genflo, Alluvial Mining /Boskalis, Rotech Subsea and Red7 Marine, where he designed, operated and promoted various types of excavation systems. These included diver-held, ROV, capital dredging, mass flow and now the highly evolved Sea-Axe. He began in his first job as a lead engineer, rising to manager / superintendent and now director of JBS Subsea.

With his extensive history and knowledge of these forms of excavation, Whyte is a wellknown and respected character in the field, including the Aberdeen oil and gas renewable fraternity. When he approached JBS to partner him on developing the Sea-Axe, using its engineering and fabrication facilities, JBS agreed and added the JBS Subsea unit to its group of companies in order to develop, manufacture and market it.

“The effort was genuine team work,” Whyte said.

Whyte reports that a 50 percent scale unit is under development for confined areas, internal structure and spud can cleaning.

His email address is alex@sea-axe.co.uk.

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