The demand for large liftboats â€” those that can work in 180 to 200 feet of water â€” keeps growing. The need for vessels that can assist in projects in deeper and deeper water is apparent worldwide, from the North Sea to the deep shelf of the Gulf of Mexico, and not all liftboats are involved directly in oil or gas exploration.
“There is still a lot of hurricane damage both to pipelines and structures beneath the water in the Gulf of Mexico and a lot of repair work topside (above the waterline) as well,” said Allen Moore, general manager of Semco, a builder of large liftboats located in Lafitte, La., whose latest boat, KS Titan 2, checks out with 280-foot legs.
Liftboats are basically vessels that drop three legs into the seabed and jack themselves out of the water to be at the same height as the platforms they are working on. To some degree they serve as hotels, supplying accommodation and food to offshore workers, and their main decks can carry tons of supplies for new construction or repair. But liftboats are also self-propelled so they don’t require another vessel to position them on site.
|Capt. Steve Sadich in front of one of the massive legs of the new liftboat at the Semco yard in Lafitte, La. The boat can work in 200 feet of water with no danger to the hull from waves or tides.|
“The longer the legs, the deeper the water liftboats can work,” said Moore. Larger boats, such as Titan 2, can work in 200 feet of water and still leave plenty of “air gap” â€” the distance between the surface of the water and the bottom of the hull â€” to account for strong waves or tidal action.
“Liftboats are very versatile vessels,” Moore added. “Ours work all over the world doing a multitude of tasks.”
Not all of these are oil-related. Titan 2’s sister ship, KS Titan 1, delivered in spring 2008, was under contract to help build a wind farm in the North Sea. It left Pascagoula, Miss., aboard a heavy-lift vessel, but on the night of Oct. 26-27, in mid-Atlantic, the transporter vessel lost engine power during a storm. The wave action and loss of steering caused the vessel to roll, and Titan I shifted to the port side, capsized and sank.
With a leg length of 280 feet, Titan 2 is an identical vessel, and KS Energy Services Ltd. of Singapore, the company that ordered both liftboats, has since substituted Titan 2 for the wind farm project.
|The liftboat, which is ABS classified, features a Furuno radar with a 21-inch display and a GPS navigation system from the same supplier. Propulsion is via two Caterpillar 3512Bs rated at 1,575 hp each at 1,800 rpm with Twin Disc MG-5600 gears.|
“The two Titans were the second and third of this class of vessel and the eighth and ninth of a similar design we have built,” Moore said.
Titan 2 is 176.5 feet long with a 113.3-foot beam, a hull depth of 13 feet and leg diameters of 8 feet 7 inches. Usable deck space is 11,000 square feet.
One of the outstanding features of the Titan design is that the cranes are mounted on the two forward legs, not on pedestals between them, giving the cranes a wider arc of travel without interfering with each other. This considerably increases deck space.
Titan 2 mounts a pair of 200-short-ton cranes with 140-foot booms. Each uses an open-loop hydraulic system powered by a Caterpillar 3412 diesel engine. The two are identical except that the portside crane has the cab on the left side and the starboard crane has the cab on the right side to maximize the clearance between the two.
“Our sister company SeaTrax in Houston did much of the design work on these unique cranes,” said Moore.
Under normal operating conditions, Titan 2 can operate in 200 feet of water with a wave height of 12 feet and wind velocity for one minute of 70 mph. Assuming 10-foot leg penetration into the seabed, the air gap is 30 feet.
|A photo taken from the main deck looking up at the underside of the crane mounted on one of the liftboat’s three legs. The crane is in the down position.|
In survival mode, the Titan class can withstand 100-mph winds and wave heights of 15 feet and still maintain a 20-foot air gap, assuming 10-foot leg penetration in a maximum water depth of 70-feet.
Titan 2 uses a pair of Caterpillar 3512B engines for propulsion rated at 1,575 hp each at 1,800 rpm. A Twin Disc MG-5600 reversing/reduction gear is used on each engine with a 5.76:1 ratio. Engines are air start and utilize box coolers to cool engine water. The engines are connected through L-drive gearboxes to Kaplan four-bladed propellers with a diameter of 79.5 inches made of a manganese-bronze alloy.
To enhance maneuverability, the vessel uses a 500-hp SMI bow thruster powered by a rebuilt GE 752 500-hp, 600-volt electric motor.
A pair of Caterpillar 3412 engines drive generators that produce 500 kW of 480V, three-phase power. Air started, they use remote radiators for cooling.
An emergency generator rated at 250 kW and powered by a Caterpillar 3408 engine is also radiator cooled with radiator mounted on generator skid. Unlike the other engines, the emergency generator is 24-volt automatic start.
|The large red reel holds the hose for the submersible pump. When the vessel is elevated out of the water, the hose can be unspooled and lowered into the water below so it can be pumped into the vessel’s tanks.|
This generator also serves as the “hotel” generator, supplying “night time” power when the liftboat is otherwise shut down. The unit is located in an area behind the superstructure and forward of the aft leg.
The superstructure is unusually large for a liftboat. “There are three levels of accommodations on top of the main deck,” Moore said. “There are staterooms with accommodations for 50 people.”
The main deck houses the galley, mess, lounge, laundry and stores. Due to the large number of workers on board the vessel, the galley is exceptionally large with six freezers and two conventional refrigerators.
Maytag supplied four washers and an equal number of dryers, and the vessel also has two potable water pressure sets, three water heaters and a pair of water makers.
One level up from the accommodations is the pilothouse, with all the latest navigation and communication gear for a vessel of this class. That includes an Inmarsat-C mobile earth station, several VHF radios, ACR EPIRB and search-and-rescue transponders, a Furuno Navtex receiver and a Furuno AIS.
A Yokogawa gyrocompass system, a pair of Furuno gyroconverters, Furuno radar with 21-inch LCD display and Furuno GPS navigation system highlight the navigation gear.
|Liftboats are only as good as the cranes they carry; KS Titan 2’s are Monarch SeaTrax LM10520s rated at 200 tons each with 140-foot lattice-powered booms. The cranes need diesels of their own, in this case Caterpillar 3412Bs running a closed-loop hydraulic system.|
Leg jacking is accomplished with a pair of Caterpillar 3412 engines rated at 764 hp each at 2,100 rpm. The engines are air start and are cooled via a remote radiator in the engine room.
Large liftboats such as Titan 2 require substantial tankage in their hull. To run all of the diesel engines on board, the fuel storage tank is 28,000 gallons â€” about the amount of transferable fuel many crew/supply boats carry. There is also a fuel day tank with 15,000 gallons capacity.
Fresh water storage is 29,200 gallons. Some is used for cooking, but much of it goes to hotel uses such as showers. Other large tanks hold 5,000 gallons of hydraulic oil and 40,000 gallons of oily water bilge.
The liftboat has a heliport capable of landing a Bell 212 or equivalent and is built to ABS standards. It is classed as a self-elevating unit with restricted service, Maltese Cross A1, AMS and SOLAS.
Semco has completed another vessel of this class for another customer and has under construction a larger unit with 300-foot legs. Even larger units are under design. â€¢