(31a) Storage Tank Thermal Breathing Under Extreme Weather Conditions

Storage tanks are generally designed to tolerate a certain amount of overpressure and vacuum. Among the possible causes API 2000 and ISO 28300 cite the variation in volume in an empty tank due to weather changes. In this regard, overpressure is caused by an increase in ambient temperatures or extreme solar radiation and vacuum by a decrement in ambient temperature or extreme rain shower intensity. In the last years Europe experienced some of its most extreme summers in history with prolonged periods of abnormally hot temperatures and droughts, eventually followed by intense tempests and floods. Unfortunately, similar occurrences ware observed elsewhere in the world.

In a recent project conducted for AIChE DIERS, the authors outlined the thermodynamic approach behind the simplified formulas in API 2000 and ISO 28300 and discussed their assumptions and limitations in relation to extreme weather situations. The impact of extreme weather on tank head space variation as well as in the local phase equilibrium is often neglected in risk analyses.

In this paper, the authors present the major conclusions of the DIERS project and discuss the suitability of API 2000 and ISO 28300 when the occurrence of extreme weather events is increasing worldwide.