Texas company designs ATB that can deliver LNG directly to vesselsJan 23, 2013 04:58 PM
Courtesy Walter Marine
An architect’s rendering of the proposed LNG-delivery articulated tug-barge designed by Waller Marine. The vessel has its own regasification and storage equipment and can transfer gas directly to ships.
Waller Marine of Houston has developed a new concept for an articulated tug barge (ATB) that will bring LNG into smaller ports where there is no LNG infrastructure.
The new vessel will allow maritime companies to use LNG as a marine fuel even if they are not located near LNG facilities or existing facilities are too costly.
The classification society American Bureau of Shipping, of Houston, granted approval in principle to Waller’s new design in October.
“We are pleased to be part of a project with the potential to improve the environmental impact of hydrocarbon emissions,” said Roy Bleiberg, director of engineering for ABS.
The new feature of this ATB is that regasification equipment is on the barge itself. The barge can act as a floating storage tank and be moored offshore near a port to supply LNG to a marine company, according to Bill Hutchins, Waller Marine’s vice president of gas solutions. When the moored barge is empty, the ATB would deliver a full barge to the mooring.
“You don’t have to go through a long permitting process for onshore, flat-bottom storage,” he said.
In addition to eliminating the need for building storage tanks, the new ATB would eliminate the need to build a regasification plant on land near the port. By loading directly from the liquefaction unit to the ATB and then regassing on board the ATB directly to a pipeline, said Hutchins, the need for storage tanks on either side is eliminated. That reduces two LNG transfer operations to and from stationary LNG storage tanks.
Hutchins sees many advantages of this delivery system compared to conventional delivery by truck: “It becomes much safer since we are eliminating transfers, it makes everything more timely, we use a lot less space this way and environmentally it is better,” he said.
The new ATB will be able to load LNG from terminals, liquefaction plants or traditional LNG carriers and transport the LNG to existing tanks, traditional LNG carriers and trucks, he said. The new vessel can transfer gas directly to ships. It can bring LNG right into a port, as long as there is a permanent cryogenic line, Hutchins said.
Owners will have the option to order barges with LNG capacities of 15,000 cubic meters, 22,500 cubic meters and 34,750 cubic meters, Hutchins said. The barges range in length from 150 feet to 600 feet, he said.
Prospective owners will be able to install duel fuel diesel/LNG engines. Waller Marine has talked to Wärtsilä, MaK Marine and MAN Engines & Components about engines for the new ATB, he said. The client will select the engine.
Waller is in various stages of discussion with American and foreign companies interested in this new ATB.
Transporting LNG using the new ATB will be cheaper than transporting by truck, Hutchins said. It follows the same economic model used in pricing barging oil compared to trucking oil. Hutchins said Waller has calculated a company could save 75 percent of the cost of transport using this new vessel.
Waller Marine has created a subsidiary company, Waller Marine LNG Services. That company will be able to offer supply contracts to marine companies to deliver the fuel right to the port, he said.
The barge will have independent Type “C” LNG tanks, according to an ABS press release. The cargo containment system is split into four longitudinally located independent tanks and each tank is isolated from hull loads, according to the release.
Independent tanks are self-supporting and are not part of the ship’s hull structure. Type “C” tanks are usually spherical or cylindrical and can be vertically or horizontally mounted, according to the website Liquefied Gas Carrier (www.liquefiedgascarrier.com).
The regasification equipment on the ATB is in the house depicted on the trunk deck as shown in the illustration, according to Hutchins.
By adding the regasification equipment to the barge, the design becomes more complex, according to Gurinder Singh, ABS project manager for this vessel’s certification.
ABS had to make sure that the location of regasification machinery is in a protected position in relation to the LNG tanks and the ventilation system on the barge, among other safety precautions.