ABS announced the availability of Guidance Notes for Building and Classing Ships Carrying Compressed Natural Gas in order to assist industry designers and operators in practical applications of novel concepts in CNG technology. As an alternative to LNG technology, CNG offers economically viable and competitive methods of rapidly monetizing natural gas in short-haul trades or certain geographic locations. The new ABS guide will facilitate CNG industry development by providing a comprehensive framework of reference material while identifying acceptable methodologies for achieving class society approval of new CNG technology.
Relatively long distances between the gas sources and markets or difficulties associated with accessing remote, deepwater offshore fields may make pipelines prohibitively expensive for otherwise promising gas projects. Since many gas-producing fields lack suitable infrastructure for liquefying natural gas, and because terminal regasification facilities may be limited, transportation of this “stranded” gas in compressed rather than liquid form offers cost and operational benefits. Gas can be loaded directly onto gas carriers from offshore production facilities, increasing safety and decreasing security concerns. It can be compressed and contained onboard, eliminating the need for costly liquefaction and re-gasification processing. CNG carriers also can discharge gas directly into terminal facilities located offshore, further minimizing potential impact to population centers and areas of high environmental sensitivity.
First applied to short hauls of small gas volumes, these developing concepts now promise a new generation of CNG solutions. Recent examples include the TransCanada proposal for a gas transport module (GTM), based upon the company’s composite reinforced pipeline (CPLP). The concept initially concentrates on developing smaller vessels and barges for river application. An alternative to conventional pressure systems is the “Coselle” vessel design, which has a containment system with small diameter pipe in coiled cylinders for longer periods of sea transport. Trans Ocean Gas proposes a unique method of CNG transportation utilizing composite pressure vessels in the hold of a ship. The fiber-reinforced plastic (FRP) pressure vessel gas containment system has applications in the national defense, aerospace and natural gas vehicle industries. Further along in commercial application is the VOTRANS (Volume Optimized Transport Storage) concept of EnerSea Transport, Hyundai Heavy Industries and Kawasaki Kisen Kiasha, which employs 2,400 modular bottles racked vertically about six inches apart, each 42 inches in diameter.
The finalized guide will be available soon on the ABS website, Rules and Guides section.