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Arctic design: Sea spray icing models to be improved

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Arctic
Sea spray icing is one of the major challenges when operating in Arctic conditions.
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Arctic design: Sea spray icing models to be improved
Olga Shipilova, DNV GL’s Project Manager for the RigSpray JIP

DNV GL is now launching an industry collaboration which will develop a simulation model that bridges functional winterisation requirements and real physical conditions for drilling rigs, production platforms and vessels. Experts from both the maritime and oil and gas industries are invited to join the new Joint Industry Project (JIP) ‘RigSpray’.

“We aim to ensure that the design of icing-mitigation measures delivers both safety and cost benefits,” says Per Olav Moslet, Arctic Technology Programme Director at DNV GL.

Today, the operational capabilities of conventional vessels and offshore structures do not meet the requirements for operating in harsh Arctic conditions. The trend towards increased activity in the Arctic and especially the ice-free areas means that the issue of sea spray icing needs to be addressed.

“Sea spray icing poses a threat on multiple levels, from blocking the operation of essential components to jeopardising stability and integrity and thus leading to an increased risk of capsizing,” explains Moslet.

A number of recognised standards, for example DNV GL’s offshore standard ‘Winterization for Cold Climate Operations (DNV-OS-A201)’, provide guidance on mitigating ice accumulation using specified anti- and de-icing procedures. The standards available today today give requirements to safety functions and to some extent describe mitigation solutions, but do not give a specific answer to how and where they should be implemented. An optimal answer to those two questions can be given by even better understanding the physical phenomenon of sea spray icing via simulation and measurements. Overall, the benefit would be an improved safety and working environment in Arctic conditions.

To deal with this, DNV GL is therefore establishing the new RigSpray JIP and invites maritime and oil and gas experts to participate.

“We have already made progress in addressing the challenge through the MarIce JIP, where DNV GL worked together with the Norwegian University of Science and Technology and Statoil to create the world’s most advanced marine-icing model. However, this needs to be developed further. The present model still lacks an accurate representation of sea spray, which is a very important parameter for ice formation. Present knowledge of sea spray generation is limited to very local metocean conditions and sporadic vessel designs. We certainly need to fill this gap with more experimental and modelling studies,” says Olga Shipilova, DNV GL’s Project Manager for the RigSpray JIP.

The first step is to develop a software tool to further understand sea spray icing using mathematical modelling and measurements. This will provide a solid basis for extending local ice estimations to a wider spectrum of metocean and structural conditions, which in turn will lead to safer and more cost-effective winterisation solutions for drilling rigs, production platforms and vessels operating in cold climate areas.