The anchor handling salvage tugs of the SX157 design are a part of the ALP Future class. Service speed is 13 knots, while their top speed is 19 knots. With a fuel capacity of more than 3,500 t, they can tow at full power for 45 days, sufficient for non-stop Trans-Atlantic/Indian, Pacific Ocean towing operations without fuel calls. The vessels are constructed by Niigata Shipbuilding & Repair, Japan.
The vessels were developed especially for this project in close collaboration between ship designer Ulstein Design & Solutions AS and ship owner ALP Maritime Services, the latter a subsidiary of Teekay Offshore Partners L.P.
A vessel of this type typically tow oil rigs, or FPSOs, from the building yards to the installation site at the oil field. In addition, these vessels are outfitted with DP2 and anchor handling capacity in order to assist during the installation/hook-up phase for the towed objects. The vessels are 88.9 metres long and 21 metres wide.
At the time of the contract signing, the ocean-going tug market was a new design area to Ulstein, and the largest single contract so far for Ulstein Design & Solutions AS. When developing the design Ulstein had to ensure that each vessel has the sufficient bollard pull and operational reliability to handle even the heaviest tows by only two vessels. Environment and fuel efficiency have also been important criteria. The vessels are classed with DNV's Clean Design and Ice Class 1B notations, which allow operation also in restricted zones. Additionally, they are equipped as anchor handling vessels including stern roller, a three-drummed winch with 400-ton hoisting capacity, and with chain lockers for rig chain. The ships have a comfortable and spacious accommodation for 35 persons reflecting long periods at sea.
Ulstein is also responsible for the deliveries of main components, such as engines, thrusters and propellers, winch, power distribution and thruster drives, control system and communication system.
The three sister vessels are in different phases of construction. Vessel number 2, the ALP Defender, will be the next one to be completed, while vessel number 3, the ALP Sweeper, was launched on 7 May 2016. The final vessel will be named the ALP Keeper.
Long Distance Towing
High bollard pull: For the towing of very large floating objects
Also equipped for: Anchor Handling, positioning, mooring
Dynamic Positioning Class II
Optimal seagoing characteristics (ULSTEIN X-BOW®)
Comfort Class Comf-V (3)
Ice Class 1B
Fire Fighting (FiFi II)
Cargo deck area: 550 m2
Four engines, capacity 18,000 kW / 600 rpm
Deck cargo 2,400 tons - 10t/m2 Max
Deadweight 4,250 tonnes