| | Volume 30 Issue 4 out now!  BACK TO THE FUTURE: WORK-SUBS RETURN | | vol. 30 - no. 3 25 April 2013 | From the North Sea (NT): A subsea work-sub could offer operational and cost advantages to the offshore industry, according to submarine designer and manufacturer Kockums.
It could be an important supporting element for the ‘subsea factory’ (SEN, 29/12) envisaged by Statoil, says naval architect Per-Ola Hedin of Kockums marketing and business development department. This would be appropriate, as it was Statoil which, back in the 1980’s, first approached Kockums with the idea.
The Swedish company has now developed two variants of its MASU – modular autonomous service submarine – which it presented at the recent Subsea Valley conference in Norway. One is a small craft, 41m long and with a displacement of 1,500t, which could handle loads of up to 50t in water and perform tasks such as installation and maintenance of subsea structures, pipeline inspection and combating oil spills.
Beat the drum
The second is larger - 60m length and displacement of 2,200t with a cargo bay in its forward section in which it is able to transport and install, using cranes and beams, modules of up to 200t in water. While able to perform the same tasks as the smaller sub, it can also install parts of subsea tree stacks and, with a cable drum installed in the cargo bay, lay cable. Both versions are equipped with dynamic positioning and a work rov, and propelled by Kockums air-independent Stirling engines.
The subsea work-sub is autonomous in several ways: once submerged, it is free of the influence of the weather and surface sea conditions. Also, it does not need a mother ship – it can sail from port to field at a rate of 9kt and operate submerged for up to two weeks. The standard crew is six to eight persons, but there is room for additional personnel.
The concept is modular in the sense that it is a flexible design. It could be configured, for example, for loads of up to 500t, says Hedin. While requiring roughly the same investment, it offers various operational advantages compared with a large intervention vessel – reduced fuel consumption, smaller crew costs and no downtime due to weather and surface conditions. These include ice, which in principle makes the sub suitable for working in Arctic areas.
Kockums is now talking to various interested companies with a view to further developing the concept and – as it is not an offshore player – finding a partner to help make the concept a reality.
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