BREAKING THE ICE

This was a short article about the icebreaking supply ships written in 2001

The arrival of the Vidar Viking in Aberdeen during April of 2001 was something of a finale. She is the third of a trio of Moss808s (Formerly Kmar808s) built for B&N Viking and is in the main identical to her two sister ships the Tor Viking and the Balder Viking. The Vidar Viking is provided with DP Class II capability, a feature which the Company say will be provided for the other ships in time and she also has a large storage reel on the winch housing.

 The ships are contracted to the Swedish government for icebreaking duties during the winter and at other times can take on any commercial opportunities which are available for large anchor-handling supply vessels.

In this way they follow the icebreakers Fennica, Nordica and Botnica which are operated by the Finnish Maritime Administration for icebreaking during the winter and are also available for other work during the summer. The main difference between the Finnish vessels and the Viking ships is the configuration of the stern. The Finnish ships were built in the normal icebreaking design with a notched stern, while the same facility in a bolt on addition in the Swedish ships.

The Balder Viking at work in the ice. Photo Bjarte Tronsden.

Commercial icebreaking is itself an exciting and skilful activity requiring specific features in the vessels. The Finish icebreakers of the sixties and seventies were built for the job, usually with two propellers at the stern and two at the bow, the latter to assist with the icebreaking. More modern designs use the raked icebreaker bow which allows the ship to ride up on top of the ice and break it with the ship's weight, a technique possibly pioneered by the Manhattan the American tanker built for transiting the Northwest passage in the 1960s.. A second feature is the ability to transfer ballast rapidly from one side of the ship to the other providing a rolling motion which prevents the ship becoming stuck. The Vidar Viking for instance has cross connected wing tanks and a pumping arrangement which can create a 10 degree list in 20 seconds. The third essential feature is the already mentioned notch stern.

Those involved in the offshore industry tend to lose sight of the fact that normal commercial cargo carrying vessels have very limited power available and even those with ice strengthened hulls will be equipped with engines commensurate with the need for an adequate transit speed combined with wonderful fuel economy. Hence, in the Baltic winter these vessels make their way northward past the edge of the ice under their own power until they are unable to proceed further. Often ad-hoc convoys accumulate as smaller ships follow larger and more powerful vessels until all will finally come to a halt. They will then call for help from an icebreaker.

If the ice is not too thick the icebreaker will approach the convoy from the bow, crunching though the ice and rolling majestically to prevent it from sticking to the sides. It will skim down one side of the convoy, then it will turn round and break the ice up the other side, slowing and then tucking itself in ahead of the leading ship. With luck everyone can then move forward until the open channel into the port is reached.

In very thick ice the third feature of the icebreaker is put to use and the vessel being rescued is pulled into the notch in the stern and effectively dragged along bodily until the port is reached, this process is less used that the collective freeing of the convoys, but never-the-less it must be available.

All these craft possibly gained their inspiration from the two ships designed by Robert Allen of Vancouver and built for Beaudrill in Canada in 1983.  These craft, the Ikaluk and the Miscaroo  were impressive in their day and, using the raked bow principle were claimed to be able to break through 15 foot ice ridges.

The Fennica and the other two vessels operated by the Finnish Maritime  Administration spend their summers contracted to the subsea specialists DSND for all sorts of underwater tasks, and are favoured for activities with requiring the use of the large A-frame on the stern, such as the prelaying of mooring systems.

In their icebreaking mode the B&N Viking ships have the notched stern bolted on and a Helideck fitted to the afterdeck, but once these items are removed their effectiveness as heavy duty anchor handling and towing vessels is unimpeded. Indeed they are provided with a wonderful set of deepwater anchor handling equipment. Unusually the tow drum is set aft of the workdrum because it is of a smaller diameter, but is still capable of storing two 1650 meter tow wires side by side. The larger diameter workdrum can store over four kilometres of 83 mm diameter wire. In all the chain lockers can accommodate 12,000 meters of 3" (76mm) chain or half a dozen semi-submersible moorings.

The four MAK engines arranged in a father and son layout and shoe-horned in to an engine room in the forepart of the ship, in what has become the standard European, mode develop over 18,000 bhp between them and offer a useful 200 tonnes of bollard pull.

It is a requirement when icebreaking for the officer of the watch to be able to see ahead and astern at the same time and to facilitate this activity both the Finnish anchor-handlers and the Swedish ships are provided with an off centre conning position, and while it may be seen as being essential for some work, standing at the position on the Vidar Viking gives one a curiously lopsided feeling and there is no doubt that ships are best conned, particularly in narrow channels and congested waters, from the centre-line.

Now that the winter has passed all three of the Viking vessels are back in the oil business. The Vidar and the Balder have been employed by Saipem in support of the Saipem 7000.  Substantial vessels of this sort are seen as being necessary to deploy the 40 tonne anchors of the crane barge. Thereafter they manoeuvred a barge alongside so that a flare boom could be lifted onto the S7000. The Tor Viking has been regularly employed rig moving since entering service and up to the third week in April had carried out over thirty rig moves. Both the Tor Viking and the Vidar Viking were employed by the Swedish Maritime Administration straight from the shipyard, the Tor icebreaking for February and March 2000 and the Vidar for February and March 2001. This year both the other ships in the team continued their commercial activities, though it is likely that they must be positioned so as to be able to take up their primary duty in the event of a sudden cold snap.

One assumes that the Viking ships will reduce the cost of keeping Sweden's port open while making the lives of supply ship enthusiasts everywhere more enjoyable; and they illustrate the fact that it is at last possible to design a dual purpose ship which is totally effective, rather than less effective in both roles .

 Vic Gibson

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