LFL ESTIMATES FOR CRUDE-OIL VAPORS FROM RELIEF TANK VENTS

In 1970, the Alyeska Pipeline Service Company was formed to manage the design, construction, operation and maintenance of the Trans-Alaska P ipeline System. The 800 mile long pipeline carries crude oil from Prud hoe Bay on the North Slope to Port Valdez on Prince William Sound. The re are 11 pump stations located along the Pipeline, each of which is e quipped with a crude oil relief tank. Because of the potential flammab le nature of the crude oil vapors being vented from the tanks, Alyeska wanted to determine the region surrounding the tanks within which the lower flammable limit (LFL) could be exceeded. Because numerical mode ls cannot accurately model the flow near structures, especially for de nse gases (as is the case here), wind tunnel modeling was conducted to provide more accurate distance to LFL estimates. The wind tunnel mode l simulations were also used to judge the effect of various modeling p arameters (i.e., site specific configurations release scenarios and me teorological conditions), and to assist in possible future refinements to numerical models. Field observations were also obtained at one of the pump stations for the purpose of validating the wind tunnel modeli ng. We project, wind tunnel scaling methods, experimental methods, con centration measurement results, distance to in estimates and compariso n between the field and wind tunnel observations are described in this paper.