Feature 2
enersea’s VOtrans
shipboard cargo
containment
system is
comprised of
many Cng bottles
made from large-
diameter steel pipe
segments.
phase and to actual class approval.’ 84 Coselle ship transporting about 250mmscf pipeline connected to a conventional single
While the commercial complexities of the of gas; a 108 Coselle ship transporting about point mooring.
various gas projects EnerSea is pursuing (in 325mmscf of gas; and a 144 Coselle ship The CGL concept deploys 80miles or more
West Africa, the Caribbean, South America, transporting about 450mmscf of gas. of large diameter steel pipeline packed within
and Asia) make it difficult to be definitive Also approved in principle by ABS, the cargo holds of a new or converted vessel.
when it comes to first ship orders, Mr Dunlop Coselle CNG ships will be deployed to carry Horizontal pipe sections are linked in a vertical
termed himself ‘very optimistic and confident’ moderate volumes of natural gas (30mmscf to serpentine arrangement, in this case referred
that 2008 would be the breakthrough year. 500mmscf) over medium distances (200km to to as a ‘bundle’. Each pipe bundle is connected
An alternative technology is being offered 2000km). in a looped manner to multiple pipe header
by Sea NG, which is also backed by big A somewhat different solution to capture groups. Bundles are arranged across the holds
hitters, having formed a strategic alliance with stranded gas was proposed at the end of 2006 of the carrier, with adjacent pipe bundles
Marubeni Corp and Teekay Shipping Corp. by private entity SeaOne Maritime Corp, of nesting together to maximise use of hold
Sea NG’s ‘Coselle’ containment system will Houston, in the shape of the ‘compressed gas space. They are housed within a covered and
typically involve 10miles of small diameter, liquid carrier’. insulated cargo area through which chilled
high-strength, but industry-standard X70 At that time, SeaOne said it planned to nitrogen flows.
pipe, coiled into a reel-like structure, called a convert three 150,000dwt conventional The gas stream would be first fed to a deck-
carousel. This carousel provides support and Suezmax oil tankers into CGLCs. mounted inlet separator at a typical scalable
protection for the transportation and stacking Also dubbed ‘LNG Lite’, this technology is load rate of 0.2bcf/day.
of the Coselle system. Each Coselle carries also approved in principle by ABS and envisages SeaOne has said that the new storage
about 3mmscf of gas and can be stacked on the the carriage of all types of liquefied gas, ranging technology is suitable for either purpose-
deck or in the holds of a ship. These stacked from C1, defined as LNG, to the C2-C5 types designed newbuilds or for converted existing
Coselles are then manifolded together using that are the preserve of LPG carriers. The CGL tonnage, particularly single hull crude oil
a system that allows for safe and efficient gas containment system would not require the low tankers facing phase-out.
loading and unloading. temperatures of LNG, nor the high pressures A single hull Suezmax tanker would be
Lyndon Ward, Sea NG director of of current CNG containment systems. Instead, convertible into a carrier capable of delivering
marketing, said that the Coselle system had gas would be stored aboard in a liquid form at up to 1.5bcf of natural gas. A typical high block
been referred to as ‘the floating pipeline’, as it is minus 40°F/C at pressure of 1400psig. coefficient vessel, such as an oil tanker, would
simply a series of coiled pipelines. ‘The natural By comparison CNG, which has been face no problem in providing the displacement
gas industry has been using coiling pipeline consistently pitched as the alternative to necessary for this type of gas carrier, SeaOne
for years in sub-marine pipelaying and the LNG technology when it comes to exploiting has said.
Coselle system is a new application of a proven remote finds, offers refrigerated compressed Meanwhile, newbuild designs are available
technology’, he said. storage systems operating at 1800psig at minus for carriers of up to 6bcf capacity. In this case,
The reel is enclosed and then filled with inert 29°C, or pressure-only systems operating at the cargo hold dimensions and configuration
gas, with Coselles subsequently contained in an 3000psig-3600psig. can be fully optimised for maximum CGL
inert-gas filled cargo house. Since the Coselles Like its CNG counterpart, the CGLC capacity, with hullforms tailored to the speed
are large, only a relatively simple manifold with proposal potentially compares favourably requirements of the market.
few valves and controlling systems is required. with LNG with regard to requiring no costly At time of going to press, SeaOne said it
The size of the ship is best defined in terms shore-based facilities which would be required had furthered its work with ABS over the
of its carrying capacity. Sea NG has developed for CGL liquefaction and regasification. configuration of its containment system
several ship designs, including: a 16 Coselle Production gas loading and sales gas for shipboard use and would make a new
ship transporting about 50mmscf of gas; an offloading would be handled by a flexible presentation of its solution in May. NA
The Naval Architect February 2008 61
NA Feb 08 -
p60-61.indd 61 05/02/2008 09:44:06
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