Publication No. 11-04-148
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Pages: 1, 2, 3, 4, 5, 6, 7, 8
Vertical asphalt tanks
Volumes and levels
SCOPE
This document applies to vertical asphalt tanks currently manufactured by Heatec (Figure 1). It defines different types of tank volumes and enables users to convert levels to volume.
Figure 1. Heatec vertical asphalt tanks.
VOLUME
This is the amount of space available for a specific use. Most of the space inside an asphalt tank is used to store liquid asphalt. However, some of the space is occupied by heating coils. And some of the space is reserved for overflow control.
It is helpful to call different spaces by names that indicate their use. These names and definitions are presented below and shown in Figure 2.
In this document volume is expressed in gallons. This is the most common unit of measure used for storage of liquid asphalt at HMA plants in the U.S.
NOMINAL VOLUME
This is the approximate capacity of an asphalt tank. This amount is usually a number rounded off in thousands of gallons. It is useful in classifying tank sizes, but is not an exact indication of how much asphalt can be stored in a tank.
GROSS VOLUME
This is the total amount of space inside an asphalt tank. It does not include the amount of space occupied by insulation. But it does include the space occupied by heating coils and the amount of space reserved for overflow control. Therefore, gross volume is always somewhat more than the amount of asphalt that can be stored in the tank.
NET VOLUME
This is the amount of liquid asphalt that can be stored in an asphalt tank. It is equal to the gross volume less the space occupied by the heating coils and less the amount of space reserved for overflow control. It ignores other components such as vent/overflow piping, fill piping, and mixer impellers because the space they occupy is not significant.
COIL DISPLACEMENT VOLUME
This is the amount of space occupied by the heating coils. In vertical tanks this space is relatively small. The number of gallons displaced by the coils is listed in Figure 2. Be sure to deduct this amount from the gallons shown in Figure 5 when converting levels to gallons.
RESERVED SPACE
This is empty space in the top of the tank reserved for overflow control. It also allows for thermal expansion of the liquid asphalt. This space extends downward several inches below the top inside bulkhead. Overflow controls cut off the unloading pump before asphalt fills this space. This space is significant. It is not included in net volumes shown in Figure 2.
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