Icebreaker/offshore vessel BOTNICA
TS Shipping Ltd. is a provider of escort icebreaking, ice management and offshore services. TS Shipping was founded in 2012 and is 100% owned by the state-owned company Port of Tallinn – the biggest port authority in Estonia, and one of the biggest Baltic Sea ports. TS Shipping is the owner of Botnica, the well-known offshore support vessel and Baltic Sea icebreaker. The company provides full management services for the vessel, including commercial, technical and crewing.
The company’s activities are seasonal. During harsh winters, its activities are concentrated on engaging in safe escort icebreaking operations in the Gulf of Finland and in Estonian coastal waters, while during the summer it renders services to the offshore oil & gas and renewable energy industries throughout the world. As oil exploration is moving farther north, the capabilities of Botnica form a perfect combination for use in the demanding Arctic environment during its short summers. Both the onshore personnel and crew on board are committed to working safely and efficiently to complete the vessel’s tasks successfully.
Finland is entirely dependent on icebreakers to keep its trade routes open in winter. Icebreakers are normally in operation from mid November until the end of May. Traditionally, icebreakers have been unemployed outside the winter season. In the early 1990s, the Finish Marine Administration began to look at alternative configurations to see if an effective icebreaker could be combined with enough flexibility to be employable elsewhere. The first result was the combined icebreaker and offshore vessel FENNICA put into service in 1993 followed by a sister ship NORDICA in 1994. They have proved to be very successful and this experience has led to the construction of the BOTNICA.
The new [MSV = Multipurpose Support Vessel] is somewhat smaller than its predecessors. FENNICA and NORDICA were 116m long with a beam of 26m and 15 megawatts of propulsion power, fed through two azimuth thrusters. BOTNICA is 96.7m long with a 24m-beam. The total engine output is15MW but under normal conditions 10MW is used for propulsion. The latest technology has been incorporated and BOTNICA is notable for two Azipod units which provide a bollard pull of 105t and a free running speed of 15 knots. The ship is capable to maintain a continuous speed of 4 knots ahead in 1.2m thick ice and the speed of 8 knots in 0.60m ice.
Azipods cost about $2-3 million more than traditional line shafting with propeller for the BOTNICA, March 1997 dollars. The system was ordered at the time of vessel contract and there was no advance procurement. BOTNICA was delivered 16 months after contract award. Initially the Azipods leaked oil, which would be fixed with time. It was suggested that oil in the bearings should be biodegradable oil. The Chief Engineer who also served on NORDICA and FENNICA said that their azimuthal propulsion system (Aquamaster) did not leak oil. He felt that the Azipods were simpler, required less space and less maintenance but had a higher initial cost. Podded propulsors worked generally very well. The Chief Engineer reports that maintenance of Azipods are slightly better (less labor) than the Aquamasters on FENNICA and NORDICA. However, both AZIPOD units aboard BOTNICA have had some lubrication oil leaks inside the pod. One unit has mild external leak of lubrication oil through the shaft seal.
The propulsion plant consists of 12 Caterpillar diesel generators vice 6 Wastrel diesel engines because the initial acquisition cost was less with the Caterpillars. The Chief Engineer would have preferred few diesel engines to lessen the maintenance requirements. With the CATS he has 144 cylinders and they require maintenance every 2000 hours of operation, but he believes the CATS are more fuel-efficient than the Wartsila engines. A life cycle cost analysis was not done as part of the engine selection process. There was also insufficient space in the machinery room for engine maintenance. He believes that the vessel is under powered and feels the power level of the FENNICA is better. With the small engines, there are many maintenance points. She requires 144 hr of maintenance every 2000 hr of operation. CAT’s are fuel-efficient 12-15 cu m/hr during DP on BOTNICA; 18 to 20 cu m/hr on NORDICA/FENNICA. Not enough space for maintenance of engines on BOTNICA. The Chief engineer wants more power and space. Vibration was because the ship is light. The problem is greatly reduced when the vessel is ballasted down. She operates icebreaking at 7.6-7.7 m draft but if she can ballast to 8 m, it helps a lot.
The bow skeg or bilge keels do not affect the flow of ice around the hull. A 6.5 x 6.5-meter moon pool is mostly used for ROV’s, but they used a small rig last year in open water. A portable large rig was built and never used and is stored at the charter’s site in Norway. The moon pool has a submergible door. It is left off in open water and the trunk of the moon pool has holes to dampen the waves inside. The door rests on the bottom in shallow water. The ship moves over and a diver attaches a cable from the crane to lift it up in place. The water is pumped out with portable pumps and then turnbuckles are placed around the perimeter to secure it for the icebreaking season.
In winter, the ship operates as an icebreaker, in summer is used for subsea intervention. The vessel is able to carry out slim hole drilling, ROV support. It can also carry out towing operations and provide cargo and equipment supply. BOTNICA includes many features already seen in two earlier vessels from Finnyards. In particular, the hull form is comparable, with its raked bow, forward and aft skeg, angles and partial chines in the underbody and the forebody, which steps in to a narrower aft section. Together, these features give excellent icebreaking capability combined with the necessary stability, seaworthiness and low motions for the offshore work.
The ship is very maneuverable and works great astern. FENNICA class is very similar but a little better, perhaps because of the greater power. Bow thrusters are very bad in ice. They shouldn’t be used and they are not used in ice. In open water (North Sea) the ship is superior. The two Azipod propulsors are supplemented by three Brunvoll tunnel thrusters in the forward skeg. Power for all units and the ship services and auxiliaries is generated by six generator sets housed into two separate engine rooms and arranged in a staggered formation to leave room for 6.5m by 6.5m moonpool in the middle of the ship.
BOTNICA has four level accommodation that provides space for the crew and additional staff for specialized offshore operations. Over the foredeck accommodation there is a helicopter platform. The aft deck is equipped with a 30m-high derrick over the moonpool and a 160t Hydrolift crane.
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