Proceedings Of The Marine

FALL 2015

Proceedings magazine is a communication tool for the Coast Guard's Marine Safety & Security Council. Each quarterly magazine focuses on a specific theme of interest to the marine industry.

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Page 41 of 94

39 Fall 2015 Proceedings • any intervening spaces, and adjacent structure, if neces- sary, to support these elements. Tank Types The IGC code differentiates between "independent" tanks and "integrated" tanks. Independent tanks are self-support- ing, do not form part of the ship's hull, and are not essential to hull strength. There are three categories of independent tanks: • Independent Type A tanks are designed primarily using classical procedures for ship structural analysis and are fully insulated, with a complete secondary bar- rier. The design vapor pressure is 0.7 bar (approximately 10 psi) and they are typically of a prismatic, volumetri- cally effcient shape. • Independent Type B tanks are designed using model tests and refned analytical tools to determine stress lev- els, fatigue life, and crack propagation characteristics. This advanced failure-mode analysis means that only a partial secondary barrier is necessary. These tanks are also fully insulated and have a design vapor pressure of 0.7 bar (approximately 10 psi). Type B tanks take one of two shapes — a spher- ical tank or a self-supporting prismatic tank. • Independent Type C tanks meet American Society of Mechanical Engi- neers Section VIII pressure vessel crite- ria and can accommodate design vapor pressures up to 10 bar (approximately 140 psi). They are fully insulated and require no secondary barrier, but they do require additional space for inspec- tion outside of the tank. Just 50 years ago, William Wood Prince, president of the Chicago Union Stock Yard, developed the world's frst lique- fed gas carrier, pioneering the safe storage and transport of liquefed gases on the waterways. 1 Now, as the U.S. enters an Energy Renaissance and is positioned to provide large quantities of competitively priced shale gas, the industry is well established with experience, engineering, and stan- dards to ensure the volatile cargo is kept safe in specialized containment systems. The International Maritime Organization's International Code for the Construction and Equipment of Ships Carry- ing Liquefed Gases in Bulk (IGC Code) and U.S. 46 Code of Federal Regulations Part 154 are just two internationally recognized regulations that govern gas carriers. According to the IGC code, the entire cargo containment system con- sists of the following elements: • primary barrier (cargo tank); • secondary barrier (if necessary); • thermal insulation; Containment Systems LNG cargo containment systems are designed for safety. by Mr. Aziz bAMik General Manager GTT North America, Inc. Liquefed Gas Production, Transportation, and Use Graphic courtesy of GTT.

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