API TR 2567:2005 pdf download

API TR 2567:2005 pdf download.Evaporative Loss from Storage Tank Floating Roof Landings.
1.4 Proposed Estimating Methods
Floating.roof tanks were segregated into the following categories for purposes of estimating landing losses:
a. internal floating-roof tanks (IFRTs) with a full or partial liquid heel.
b. external floating-roof tanks (EFRTs) with a full or partial liquid heel, and
C. IFRTs and EFRTs that drain dry.
The two modes of vapor loss (standing idle and filling) are evaluated differently for each of these categories of floating-roof tanks.
1.4.1 Standing Idle Loss.
The first two categories are described as having a liquid heel, which is a reference to stock liquid remaining in the bottom of the tank as it stands idle after having been emptied (see Figure 4). This heel of stock liquid provides a continuing source of vapors to replace those expelled by breathing (in the case of an internal floating-roof tank) or wind action (in the case of an external floating-roof tank). For each of these cases, then. standing idle loss is a process that is repeated on a daily basis.
The third category is described as drain dry, which refers to a tank that is designed to drain its entire bottom to a sump (see Figure 5). The tank’s withdrawal line is located in the sump in a manner that leaves virtually no free-standing liquid in the tank after it has been emptied. The only stock liquid available for evaporation, then, is that which clings to the tank bottom and other wetted surfaces under the floating roof. Once this thin film has evaporated, there is no free stock liquid remaining to replenish vapors under the floating rooI Standing idle loss t’rom a drain dry tank does not continue to occur day after day, but rather is limited to a one-time evaporation of the liquid clinging to the wetted surfaces.
A tank only qualifies as a drain-dry tank if all of the free-standing liquid has been removed. If the tank drains to a sump, hut a heel of free-standing liquid is left in the sump. then the tank would he considered to have a partial liquid heel. Flat bottom tanks that have most of the free-standing liquid removed by means of a vacuum truck typically have pools of liquid remaining, and should generally be considered to have a partial heel as well.
1.4.2 Filling Loss.
Each of these categories experiences filling loss in addition to the standing idle loss. The filling loss is assumed to include vapors from two sources. The first source is those vapors that remain under the floating roof at the end of the standing idle period.