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Flow-X─ Function Reference
2-9
Introduction - Flow-X Function Library
Chapter 2 - Introduction
This document describes the spreadsheet functions for the Flow-X series of flow computers. It also
provides background information on related standards and calculation methods used in the industry for
quality and quantity measurement of hydrocarbon and other type of fluids.
The document serves as a reference manual for application engineers who have in-depth knowledge of
the configuration software used for programming the Flow-X products.
Flow-X Function Library
The Flow-X series of flow computer uses Microsoft Excel as its configuration environment. Each Flow-X
application consists of a single Excel workbook that contains one or more worksheets.
Flow-X functions are configured as regular Excel functions. By using the output of one function as an
input (argument) in another function a complete calculation scheme can be made. Functions can be
defined on multiple sheets in order to organize the application.
API Petroleum Measurement Tables
History
The first version of the API Petroleum Measurement Tables was published in 1952. In those days
measurement readings were taken manually and the tables were used to convert the observed density
or gravity at the observed temperature to the value at the reference temperature. So the table values
were the actual standard.
The 1952 Tables consists of 58 tables containing all kind of correction and conversion factors used in
the measurement of hydrocarbon liquids. Each table deals with a particular conversion of units,
correction of density, or correction of volume. The 1952 tables that have to do with the conversion of
density and volume are: 5, 6, 23, 24, 53 and 54.
Table 5, 6, 23 and 24 convert density or volume to or from to a reference temperature of 60°F, while
tables 53 and 54 refer to 15°C.
In 1980 a complete new set of tables was published together with computer routines to allow
electronic devices to automatically calculate the volume conversion factors and API gravity / (relative)
density at the reference temperature. Back then most electronic devices were not capable of
performing double-precision floating point calculations, so the standard prescribed all kind of rounding
and truncating rules to make sure that the calculations would always provide the same result. For the
1980 version the calculation procedures are the standard rather than the table values.
In the 1980 version, which is also referred to as API-2540, the tables are divided into 3 product groups
and a letter designation was used to distinguish between the sub-tables. "A" was used for crude oil, "B"
for refined products and "C" for special applications. The 1980 tables, however, did not cover the LPGs
and NGLs density ranges and the 1952 Tables were left valid for these products. Furthermore, the
lubricating oil tables (designated as "D") were not complete at the time of the printing in 1980 and
were released two years later. As opposed to the A, B and C tables no implementation procedures were
defined for the D tables.
In 1988 the Institute of Petroleum released its Paper No. 3 with tables 59 and 60 that are based on a
reference temperature of 20°C.
This resulted in the following Petroleum Measurement Tables dealing with the conversion of volume
and density to and from a reference temperature.