8.7.4 Combining Trim and List Corrections
This is called the "observed temperature." In order to calculate the volume of a liquid at standard temperature, a correction factor is applied to the volume at the observed temperature. This correction factor is called the "Volume Correction Factor" (VCF) or "Correction for the Effect of Temperature on the Liquid" (CTL). The latter term is used more in dynamic measurement such as meter proving; however, both terms refer to the same thing. The function of this correction factor is to adjust the volume of liquid at observed temperature to its volume at a standard temperature, by calculation. These correction factors are usually obtained from the Petroleum Measurement Tables, API MPMS Chapter 11.1, ASTM D 1250 or IP 200. These tables were a joint effort of API, ASTM and IP, hence the three different designations for the same set of tables. These tables are entered with the observed average temperature and an API Gravity at 60 ° F, Table 6 series; a density at 15 ° C, Table 54 series; a relative density at 60 ° F/ 60 ° F, Table 24 series; or, a coefficient of thermal expansion, Table C series. To determine which table is applicable you should be guided by the below table.
8.8 To Calculate Gross Standard Volume (GSV), Shore Tanks and Marine Vessel’s Tanks Gross Standard Volume (GSV) is calculated by multiplying the gross observed volume by the volume correction factor.
Caution must be exercised when applying trim and list corrections collectively. In many cases these corrections are only applicable when the other condition does not exist. When both conditions do exist, it is preferable where possible, to eliminate one of them. List is usually the easiest for a vessel to remove. 8.7.5 Free Water Volume (FW) This is obtained from the vessel's capacity tables which are entered with the free water innage or ullage. As with any liquid in a marine vessel's tank, free water is subject to the effects of trim and list and the previously referenced trim and list corrections are applicable to free water, provided the free water is touching all bulkheads of the tank. If the free water does not touch all tank bulkheads, a wedge condition exists.
GSV = GOV x VCF
8.8.1 Volume Correction Factor (VCF) If a quantity of oil is subjected to a change in temperature, its volume will increase as the temperature rises or decrease as the temperature falls. The amount of change is determined by the thermal coefficient of expansion of the liquid. In the U.S.A. and many other countries, crude oil and petroleum products are sold on the basis of volume at standard temperature. The two most common units are "barrels at 60 ° F" and "cubic meters, m 3 at 15 ° C". Of course, the temperature of the liquid when measured will be at whatever temperature it happens to be stored at.
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