Besides the stream of new builds taking to the water throughout the average year, many other ships receive a transformation to give them a new lease of life and an entirely new revenue earning career as a sea going or static concern. One sector that has seen several workhorses effectively transformed into new builds by way of a conversion makeover is that of the Semi-Submersible Heavy Transport vessel. 

A New Product 

The 66,671gt oil Products Tanker Tordis Knutsen was built in 1993 as Yard No. 288. With a summer deadweight of 123,848 the 204m long, 42m beam and 9.4m draught shuttle tanker was built by Astilleros La Naval in Sestao, Spain. This shipyard has over 100 years of shipbuilding history and, since 2006, is 100% privately owned. La Naval has always been dedicated to the design and construction of high value special vessels and, in the 1990’s, built Shuttle Tankers, oil and Product Tankers and Chemical Tankers. From 2000 onwards they began the design and construction of LNG Tankers with three 138,000m3 ships built between 2000 and 2007. Other products include the Suction Dredgers, Ro-Pax Ferries plus custom built vessels for the offshore oil & gas and offshore Wind industries. The Tordis Knutsen was acquired from Knutsen OAS Shipping AS (that itself has a history dating back to 1896 and is based in Haugesund, Norway) by offshore Heavy Transport of Oslo, Norway in 2014. The company took delivery of its first converted heavy lift vessel, the 31,021gt/1981 built Eagle, in November 2006. The second converted heavy lift vessel, the 31,027gt/1981 built Falcon, was delivered in early April 2007. The third vessel, the 38,722gt/1989 built osprey, was delivered in June 2008 and the fourth vessel, the 44,657gt/1989 built Hawk, was delivered in December 2008. Following a mandatory offer in October 2008, the Arne Blystad group acquired 89% of OHT’s shares. Then known as ocean Heavy Lift ASA (OHL) the company was delisted from the Oslo Stock Exchange in December 2008. The new combined company resolved to change its name from ocean HeavyLift ASA to offshore Heavy Transport AS in February 2009.

The third and fourth heavy lift ships were formerly owned by Songa Ancora, part of the Arne Blystad group. During its 8 year history OHT has built a solid client base, which includes all industry majors within all client segments, and has, through this, built a reputation of being a quality transport provider. OHT AS is now one of the most experienced heavy transport vessel operators in the world with additional offices established in Singapore, Korea, Shanghai, and Houston. OHT’s now five-strong fleet of semi-submersible open deck heavy lift carriers are suitable for dry transportation of offshore drilling rigs, offshore modules and all other oversized floating and non-floating cargoes. The cargoes are typically extremely large and heavy (up to 40.000 tons), and, in many cases, are high value constructions. The loads catered for include offshore drilling rigs, floating production units, SPARS/TLPs (Tension Leg Platforms), oil field equipment and modules, dredging equipment and fully erected container cranes or similar truss structures. 

Project Transformation

For her conversion from a shuttle tanker to a heavy lift ship the Tordis Knutsen went to the Qingdao Beihai Shipbuilding Heavy industry Co. Ltd. (BSIC) shipyard, which was established in 1898 and is now one of the key large shipyards of the China Shipbuilding industry Corporation (CSIC). The yard moved to Haixiwan in Qingdao’s Economic and Technical Development Zone in 2004 with the full shipbuilding operation established there by the fourth quarter of 2008. BSIC has more than 330 hectares of land, 9 km of coastline, nearly 6 km of wharf length, two shipbuilding dry docks (500,000 dwt and 300,000 dwt each), two ship-repairing dry docks (300,000 dwt and 150,000 dwt each), one floating dock for ship-repairing (100,000 dwt), and relative equipment & facilities (including for 600 ton gantry cranes, one 350 ton gantry and one 200 ton gantry crane. During the rebuild the cargo tanks were removed and the hull sides were cut down between reinforced bulkheads forward of the superstructure and at the bow. The double skinned hull was heavily reinforced longitudinally to create a uniform deck load capacity of 30 tonnes per square metre along the 129.5 metre long free deck, which also has a breadth of 42.5 metres. The total area of the free deck is 5,400 square metres. In her new form the albatross has a 34,797 tonne deadweight compared to the 123,000 tonne deadweight when a products tanker. The ship’s length overall is 204.325 metres with a moulded hull depth of 11.85 metres and maximum sea going draught of 8.575 metres. The reinforced cargo deck allows for a large variation in payloads and the ship also has the ability to carry out load-out or load-in operations with draughts as low as 5.5 metres. In a number of shallow ports the low draught capability will be an operational advantage. The heavy lift ship is required to semi submerge to load project cargoes by way of float on, float off as well as accepting loads from quaysides. The albatross can submerge her working deck to 9.5 metres below the surface and is capable of loading modules weighing over 10,000 tonnes. This depth also permits the loading of large floating cargoes equipped with spud cans or thrusters protruding beneath them. During the conversion, OHT focused on improvements to the ballasting speed. The vessel can be ballasted faster than her fleet mates as she has improved arrangements for pumping, ballast distribution and ventilation. A totally new and robust ballast system has been installed comprising six centrifugal pumps with a combined capacity of 14,000 cubic metres per hour. The entire system is fully redundant which offers the greatest possible level of safety. Furthermore the stability of the vessel is improved which allows for the ballasting/de-ballasting of more tanks simultaneously. The overall result is a faster ballasting operation for float on/float off cargoes and it is also a huge advantage for roll on/roll off in areas where there are considerable tide differences. Generally speaking a ballasting operation for a float on cargo lasts from 6 to 8 hours depending on the weight of the consignment and the ship is equipped with 58 ballast tanks. The ship uses the Amarcon octopus motion monitoring and forecasting advisory suite, as previously delivered to OHT’s other heavy lift cargo vessels. The now tried and tested system, from a subsidiary of Swiss company ABB, improves the safety and efficiency of critical heavy lift transportation operations.

The conversion project involved the use of both old and new equipment. The new included the ballast/pump system as mentioned above plus the switchboards, a stern anchor and additional transverse tunnel thrusters bringing them to a total of three. Two HRP 3011 RT 1617/1000kW thrusters are located in the bow plus one HRP 3011 RT 1617/1000kW unit at the stern and these will of course enhance manoeuvrability, an advantage both in confined areas as well as for sailing in heavy weather. Sister ship Vigdis Knutsen (66,671gt/built 1993) acted as donor ship for some components such as pumps, winches and cranes a total of four electro-hydraulic cranes are now carried by the albatross, two with a 15 tonne capacity at a 26.5 metre outreach and two with a 5 tonne capacity at a 16 metre outreach. The superstructure on the ship was enlarged to cater for a total of 39 personnel plus the docking and discharging equipment located on the bow, whilst the vessel served as a tanker, has been removed. Instead a new navigation bridge has been added on the bow, measuring 9 metres by 9 metres. This fully equipped installation is used when the cargo carried obscures forward visibility from the main wheelhouse. A ballast control room is also housed here. 

Back To Sea

Taking the albatross wherever she needs to go is a MAN B&W 6S70MC, 20,300hp main engine that drives a single 7800mm diameter Rolls Royce 4-bladed controllable pitch propeller. A Becker rudder is installed and, during conversion, the vessel was fitted with a Mewis duct near the propeller. The sea trials demonstrated a speed in excess of 15 knots and produced very promising consumption figures.

The service speed is 14 knots with an operational range of 26,000 nautical miles. On board power and services are provided by four 1,800bhp Bergen auxiliary diesel engines. The rebirth of the ship took place in July 2015 after her 12 month transformation. Following delivery to offshore Heavy Transport AS the albatross undertook her first deployment on 30th august, leaving Shanghai loaded on 3rd September 2015 bound for the Black Sea port of Novorossiysk (Russia) where she arrived on 5th October. No details of the cargo were available.

Technical specifications