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Offshore Wind Journal

Offshore Wind Journal

Motion monitoring reduces risk for offshore windfarm servicing

Thu 02 Mar 2017 by Martyn Wingrove

Motion monitoring reduces risk for offshore windfarm servicing
Jon Arne Silgjerd: The VMMS will warn vessel operators if the risk is too high

Automasjon og Data is testing its vessel motion monitoring systems (VMMSs) on a variety of vessels servicing offshore windfarms. The systems have proved to be useful to vessel owners in improving the safety of crew and engineers and reducing damage to their assets. A VMMS can improve safety during critical operations and improve the health of technicians during transits from ports to offshore windfarms.

Vessel motion can be one of the limiting factors in transferring service engineers to offshore wind turbine structures. If the motion is too extreme, then service operations should be delayed or aborted to prevent accidents or damage, said Automasjon og Data managing director Jon Arne Silgjerd.

During the transit to the offshore windfarm, engineers and crew can be affected by seasickness, which affects their performance or can mean technicians are unable to work, said Mr Silgjerd. “Our VMMS for windfarm workboats can monitor the risk of getting seasickness. If there is that risk, the vessel operator can slow down, or change direction to reduce the likelihood of seasickness,” he added. The vessel’s motion is displayed on a workstation to warn crew of the risks to their passengers.

During the landing phase, the system can reduce the risk of injuries or accidents. “When the vessel is on site, there could be dynamic impacts on wind turbine foundations,” Mr Silgjerd explained from the exhibition floor at Riviera’s Annual Offshore Wind Journal Conference, held in February in London, UK. “We can measure that, and measure slippage of vessels against the foundation, and can predict the risk.”

He continued: “The VMMS will warn the vessel operator if the risk is too high. The vessel then needs to wait until the risk is lower, or turn back to port. So, vessel operators do not have to risk the safety of engineers during ladder transfers to wind turbines.” Vessel owners could even keep their vessel in port if they know in advance that vessel motion will be too high for safe offshore operations. This would be a cost and time saving for owners and subcontractors.

The VMMS has up to three motion sensors that are linked to a computer that records the data and calculates the motion. The key motion parameters are displayed on a workstation, so the crew are aware of risks during critical operations. The sensors measure vessel pitch, roll, heave, surge, sway and yaw. There is also an impact sensor on the bow to measure pressure between the vessel and the foundation. Accelerations can also be measured in the passenger cabin for the analysis of comfort parameters.

Vessel owners can also add accelerometers, inclinometers and meteorological sensors. Another addition can be a down-looking radar for wave and air gap measurements. Data is transferred wirelessly from the sensors to the onboard computer. Data can also be sent to shore for tracking and further analysis, or it can be stored on board a vessel for later analysis or for incident investigation.

Mr Silgjerd said the VMMS has been tested on different vessels for a couple of years by the Carbon Trust. Denmark-headquartered World Marine Offshore has used Automasjon og Data’s VMMS on two of its Windserver vessels. Japanese vessel owner Tokyo Kisen Co, too, is using the system on catamarans that are designed for transporting and transferring technicians to offshore windfarm structures.

“We installed our system on one of these vessels, which has been going out to floating wind turbines, to test how the vessel behaves in different sea states,” said Mr Silgjerd. “There is an enormous amount of data to be analysed and reported to Tokyo Kisen.”

He expects more interest from existing users of the VMMS and to pick up more tests and contracts. Mr Silgjerd commented: “This year, Tokyo Kisen will carry on with additional testing. We also expect that the Carbon Trust will continue to support our data analysis on windfarm crew transfer vessel behaviour in different sea states.”

Automasjon og Data also provides systems for weather stations, gangway monitoring, wind profiling, helideck monitoring, and measuring vibration, dynamic impact and structural strain.

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