These Losses are called standing idle Losses. The breather vent remains open until the roof is again floated, so whenever the roof is landed, vapor can be lost through this vent.
Then, a vapor space is formed between the Floating roof and the liquid. To prevent damage and to equalize the pressure, a breather vent is actuated.
The equations needed to estimate Landing Losses from internal Floating roof tanks are contained in Table equations for external Floating roof tanks are contained in Table and equations for drain-dry Floating roof tanks are contained in Table The following sections explain these equations in more detail.ģ Standing Idle Losses After the Floating roof is landed and the liquid level in the tank continues to drop, a vacuum is created which could cause the Floating roof to collapse. This relationship may be written in the form of an equation: LLLTLSLFL=+ (2-10) where: LTL = total Losses during roof Landing, lb/yr LSL = standing idle Losses during roof Landing, lb/yr LFL = filling Losses during roof Landing, lb/yr The group of applicable equations to estimate the Landing Losses differs according to the type of Floating roof tank that is being used. Therefore, these emission estimate calculations are applicable each time there is a Landing of the Floating roof.Ģ The total loss from Floating roof tanks during a roof Landing is the sum of the standing idle Losses and the filling Losses. These emissions continue until the tank is refilled to a sufficient level to again float the roof. However, when the tank is emptied to the point that the roof lands on deck legs, there is a period where the roof is not Floating and other mechanisms must be used to estimate emissions. 1 DRAFT 6/30/06 Insert this on Page before Section Floating Roof Landing Losses21 When using Floating roof tanks, the roof floats on the surface of the liquid inside the tank and reduces evaporative Losses during normal operation.
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