Breathing of partially saturated headspaces in near-atmospheric storage tanks

Vapors in the gaseous headspaces of uninsulated near-atmospheric storage tanks contract and condense due to weather cooling by wind or precipitation. The latest editions of API 2000 and ISO 28300 standards recommend engineering reviews for uninsulated hot tanks. If those reviews are performed using the state-of-the-art literature models, headspaces are assumed saturated with vapors. However, vapors in the headspaces of tanks with frequent turnovers are seldom saturated, and condensation may be overestimated.

In this paper the authors present the first method to address thermal inbreathing of partially saturated single-component headspaces in near-atmospheric storage tanks. The comparison with available measurements from the open literature involving tanks with saturated headspaces infers that this simplified approach tends to minimize overestimation of the inbreathing requirements.