API TR 2569:2008

INTRODUCTION This report addresses evaporative loss from internal floating-roof tanks (IFRTs) with closed vents, a subject not currently addressed by API. Nomenclature is provided in Appendix A. The API Manual of Petroleum Measurement Standards Chapter 19, Section 1 (19.1) addresses evaporative loss from fixed-roof tanks, and specifically excludes fixed-roof tanks that have an internal floating roof (19.1.1.1). The API Manual of Petroleum Measurement Standards Chapter 19, Section 2 (19.2) addresses evaporative loss from freely-vented internal floating-roof tanks, and specifically excludes 'closed internal floating-roof tanks (that is, tanks vented only through a pressure-vacuum relief vent, blanketed with an inert gas, vented to a vapor processing unit, or otherwise restricted from being freely vented)' (1d).