LNG Tank-top fires and Radiation Exclusion Zones

摘要

LNG terminal radiation exclusion zones are prescribed not to exceed 5kW/m2 beyond the siteboundary. The determination of critical isopleth is to be made using the computer codeLNGFIRE3, or an equivalent verified model – none as yet approved. And for weather conditions– valid for not less than 5% of the time – selected to yield the maximum influence. In recentFERC submissions, proponents have made, and the FERC accepted, arguments that the largestsingle fire that must be considered is one located on the top of one LNG storage tank – typically80 m in diameter and some 40 m or so high containing about 140,000 m~3 of LNG. For such firesit has yet to be shown that they may be extinguished by fire fighting. Furthermore no data existsto verify LNGFIRE for that size and for tank-tops. LNGFIRE has only been verified for LNGpool fires located on the ground and at sizes up to 35 m in diameter. The application of LNGFIREto tank-top fires is not appropriate for several reasons: the code presumes a fixed SEP foroptically thick flames; a constant wind speed with no change with elevation; no flame drag abovea tank elevation of one meter; and no aerodynamic interaction between the flame and the tank.This paper examines the validity of its use for the regulation’s purpose by utilizing the NIST CFDcode FDS to model the proposed incident. The paper demonstrates the inappropriateness ofLNGFIRE and moreover illustrates potential knock-on effects – such as the possible loss of tankcontainment, and the exposure to a second, in-line tank – are likely thus yielding greatlyincreased radiant exposure to the public in addition to critical exposure to plant.