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40 Proceedings Fall 2015 www.uscg.mil/proceedings Membrane tanks (the predominant type of integrated tank) rely on the mechanical strength of the inner hull for sup- port and consist of two relatively thin complete membranes to contain the liquefed gas. These are separated by insu- lated inter-barrier space layers that transmit the cargo load and any internal pressure to the inner hull. As with Type A and B independent tanks, membrane tanks have a design vapor pressure of approximately 10 psi. GTT Gaztransport & Technigaz SA is the exclusive provider of the two main types of membrane tank technology: • the MarkIII system consists of one primary metallic membrane made of corrugated 304L 2 stainless steel and one triplex composite 3 secondary membrane, separated by fberglass-reinforced polyurethane foam; • the NO96 system consists of two identical metallic mem- branes made of invar — a 36 percent nickel/steel alloy. Both insulation layers are made of prefabricated ply- wood boxes flled with expanded perlite. The next generation of membrane tanks, MarkV and NO Max, will offer further value to customers and may be ready for ships in operation as soon as 2018. What's in it For Us? Regarding North America, abundant resources in shale gas will soon lead the U.S. to become an LNG exporter. More- over, due to this abundant and affordable domestic natural gas supply and stricter marine emission regulations now in force, LNG-fueled marine vessels and LNG bunker barges/ vessels are being and will be increasingly built in the U.S. In this respect, the U.S. Coast Guard will be crucial for the success of those projects, especially to ensure safety in an industry under rapid expansion. About the author: Mr. Aziz Bamik joined GTT in 1999 and is currently general manager of GTT affliate GTT North America in Houston, Texas. Before assuming this position, he occupied various positions at GTT SA, including research and development engineer, project manager, and director of business devel- opment. He received his degree in engineering from Ecole Supérieure de l'Energie et des Matériaux in Orleans, France, in 1998. Endnotes: 1. "LNG Shipping at 50 — Methane Princess sets the scene," SIGTTO/GIIGNL com- memorative publication, 2014. 2. This (304L) is the designation of the stainless steel type (18%Ni-10%CR alloy). 3. Triplex is a laminated material which is made of two fberglass cloths (for the mechanical strength) and an aluminium foil (for the tightness). Membrane Technologies The worldwide market for liquefed natural gas (LNG) is growing, and the demand is expected to double within the next 10 years. Additionally, international regulations mandate lower emissions and ship owners are demanding more efcient containment systems with lower boil-of rates (BOR) and more efcient engines. To meet these customer requirements, GTT membrane technologies ofer lower boil-of rate systems: the NO96-GW, NO96-L03, NO96-L03+, and MarkIII Flex, the last two of which ofer BOR of less than 0.10 percent per day. Approximately 75 percent of the global feet of current LNG carriers and 84 percent of LNG carriers on order contain membrane tanks. Graphic courtesy of GTT. Independent Spherical Tank Self-supporting Prismatic Type B Membrane