In early 2006 the first author notified the Society of International Gas Tanker and Terminal Operators(SIGTTO) of his concerns that fire exposure of LNGC tanks insulated with foam plastic insulation couldcause loss of cargo-insulation efficacy leading to the potential for catastrophic failure of the remaining tankson the carrier. In response, SIGTTO formed a Working Group (WG) in July 2006 to evaluate the effects offire on LNGC cargo containment systems. In February 2007 the United States Government AccountabilityOffice (GAO) issued the report Public Safety Consequences of a Terrorist Attack on a Tanker CarryingLiquefied Natural Gas Need Clarification [1], stating that "The leading unaddressed priority ... was thepotential for cascading failure of LNG (Carrier) tanks". The SIGTTO WG produced its final report inMarch 2009, Report on the Effects of Fire on LNG Carrier Containment Systems [2]. The WG found that givensufficient heat absorption by polystyrene foam insulation in an external fire scenario total insulation meltthroughcould result, depending on the intensity and duration of fire exposure. The SIGTTO report stated,in justification for recommending additional study of the issue of vulnerability to fire of foamed plasticinsulation: "The response of the insulation system to heat, with time, is unclear; a detailed understanding ofrates of insulation degradation and recession was not available for the structural arrangement of an LNGcarrier". This paper presents new experimental measurements of degradation rates of polystyrene foaminsulation as a function of applied heat intensity. In combination with an improved mathematical modelwhich accounts more realistically for the degradation of the insulation under fire/heat exposure, these dataindicate that complete failure of the insulation covering the above-deck part of a Moss Sphere tank, shieldedonly by an aluminum foil covering and the steel weather cover, could occur within approximately 10 minutesfrom the start of a tank-enveloping LNG fire on water.
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