© 2019 Department of Petroleum Resources. All rights reserved Department of Petroleum Resources (DPR) PROCEDURE GUIDE

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4.1.3.2 For the correction to be valid, however, the roof should be fully floating. In most
cases, floating roof displacement charts are either provided along with the
calibration tables of the tank or in the alternative is supplied. If neither a table nor a
formula is supplied in the tank calibration table, the following steps shall be taken to
obtain the appropriate roof displacement.
4.1.3.3 Convert the SG/Density of petroleum and petroleum product at laboratory
temperature to that at 60/60OF or 59OF using ASTM table 23A or 53B respectively.
4.1.3.4 Then obtain the SG/Density of petroleum and petroleum product at tank
temperature by converting that at 60/60ᵒF or 59ᵒF using ASTM table 23A or 53B
respectively.
4.1.3.5 Calculate the roof displacement by using the relationship W/T= Displacement, where
W = Weight of roof in long ton as given in the relevant tank table, and T = density at
tank temperature obtained from (4.1.2) above.
4.1.3.6 Subtract the roof displacement obtained (i.e. W/T) from the gross volume of tank
content at tank temperature to obtain the gross volume of petroleum and
petroleum product in storage in barrels/cubic meters. Tank content at tank
temperature is obtained by referring the tank dip to the appropriate tank calibration
table. Thereafter, proceed with other calculations to obtain the net volume and
weight of petroleum and petroleum product in the tank as set out under section 2.0
above.