VESSEL REVIEW | Karen – Small but versatile offshore dive boat for northern Norway

Norwegian builder Hukkelberg Boats recently delivered a new multi-purpose small craft to a local maritime contractor that provides a wide range of subsea services to customers in the aquaculture, marine construction and public sectors.

Named Karen, the BV-classed workboat will function primarily as a lightweight dive support vessel and as a mobile platform for remotely operated vehicles (ROVs) that are used in subsea inspection duties in Norway's coastal and offshore waters.

The development of Karen came about after Hukkelberg was tasked by local marine contractor Finnsnes Dykk and Anleggservice to design and build a self-propelled dive support and ROV inspection platform that would have excellent seakeeping properties as well as the ability to operate in the waters of northern Norway, where cold, dark, and inclement weather is the norm. As such, the boat and its equipment have been designed to be able to withstand years of heavy-duty professional use in that corner of the world.

Hukkelberg claims the biggest challenge in developing the new boat was finding enough space for the necessary dive support and ROV inspection equipment in a hull that is just under 15 metres long. Further, not only must all of the installed equipment fulfil their intended purpose, they must also remain easily accessible and serviceable without hindering daily operations.

Weight distribution was also a key factor in placing the equipment to ensure that the boat could stay afloat and upright as well as be capable of sailing at high speeds. Considerable effort was thus also placed on reducing the weight and optimising the hull's design so that the desired speeds could be achieved even as a diverse standard load is carried during regular operations.

Consequently, the finished workboat is a small monohull craft that is capable of delivering the same range of surface-supplied diving operations that have been traditionally performed by larger catamaran vessels, but with the added benefit of a high operating speed that would allow it to respond quickly to time-critical situations over a large area.

Karen has an LOA of 14.92 metres, a beam of 3.68 metres, a draught of only 69 centimetres, and space for four operators. Two Yanmar 6LY440 main diesel engines connected to two ZF 280 gearboxes drive a pair of Hamilton HJ322 waterjets to deliver a maximum speed of 35 knots and a cruising speed of 30 knots.

The boat's central feature is an onboard diving system developed by Safe Air Diving of Denmark. Hukkelberg said the construction of the boat had also marked a significant change in how onboard diving systems are installed. Specifically, Hukkelberg and Safe Air Diving collaborated on the development of a new type of compact diving system that could be integrated on small vessels as they are being designed as opposed to the traditional method of retrofitting an existing system on a boat already in operation.

This means that dive support vessels, especially smaller ones, no longer need to undergo major modifications in the future just so they could accommodate the necessary equipment since the equipment was designed from the outset to fit in the hull as seamlessly as possible and without compromising safety or impeding performance.

The diving system includes lightweight composite gas supply tanks with a total capacity for 80,000 litres, custom-built umbilical racks on the aft deck for keeping equipment within easy reach and for offering seating for divers while they are being kitted up, wearable heat vests for the divers, a tender system, and a video recording system. The diving supervisor sits at an ergonomically designed central dive control station that includes digital depth displays and bailout pressure monitoring as well as digital dive profile recording in compliance to Norwegian regulations for professional diving activities. The aft deck has a flush and hazard-free surface and also comes equipped with handholds to enable divers to safely get in and out of the water.

Aiding Karen in its regular operations is a stabilising gyro system that could reduce rolling by as much as 90 per cent. Because the boat is more stable, it is possible for surface-supplied diving operations to be carried out safely under a wider range of weather and sea conditions compared to less capable craft.

The boat also features a Palfinger deck crane, a fully integrated hydraulic system with auxiliary connections above deck, a fully integrated high-pressure washer, a Fisher Panda 230VAC generator, and LED deck lighting and work lights. The lights are particularly important to ensure safe operations during the winter months in northern Norway, which are also characterised by only five to six hours of sunlight each day.

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