ISO 91:2017 pdf download.Petroleum and related products — Temperature and pressure volume correction factors (petroleum measurement tables) and standard reference conditions.
Custody transfer of crude petroleum and its products are generally transacted in volumetric quantities. Since crude oils and petroleum products have relatively high coefficients of thermal expansion and compressibility, volumes are corrected to standard conditions of temperature and pressure in order to provide a meaningful and consistent basis for measurement. The definition of standard reference conditions is therefore of fundamental importance in measurdnwnt, calculation and accounting of petroleum quantities.
Volume correction factors are used to account for the thermal expansion of liquid hydrocarbons and convert observed volumes to volumes at standard temperature and pressure. Tables of volume correction factors were originally developed by collecting empirical data relating to the volumetric change of hydrocarbons over a range of temperatures and pressures. Cooperative international work on volume correction factors dates from 1932. The temperature volume correction factor tables (petroleum measurement tables) referenced in ISO Recommendation (R) 91:1959111 were developed during the late 1940s and published jointly by the American Society of Testing Materials (ASTM) in 1952 and the Institute of Petroleum (IP) (metric edition) in 1953191. These tables corrected to standard temperatures of 15 °C and 60 °F only, and were based on data for crude petroleum and petroleum fractions published in 1916 by the (United States) National Bureau of Standards (NBS) and some later data on natural gasoline reported in 1942. These 1952 tables were referenced in API/Standard 2540- 19661101 (also designated ASTM D1250-56). A few amendments to ISO/R 91 resulted in the publication of a second edition in 1970121. ISO/R 91:1970/Arnd 1:19751.iI was published in 1975 for tables based on a reference temperature o120 °C.
In the early 1970s. it was demonstrated that the previously published tables were not satisfactorily applicable to many crude oils of current economic importance. A revised standard was published in 1980 by the American Petroleum Institute as the API Manual of Petroleum Measurement Standards (MPMS) Chapter 11.1 (also designated API/Standard 2540. ASTM D1250-80 and IP 200/80) following the development of a new database by API in cooperation with the US NBS. This study
ISO 91 refers to temperature volume correction factors, which allow users to convert volumes. measured at ambient conditions, to those at reference conditions for transactional purposes. ISO 91 also refers to compressibility factors required to correct hydrocarbon volumes measured under pressure to the corresponding volumes at the equilibrium pressure for he measured temperature.
TabhLl shows the defining limits and (heir associated units of correction factors referenced in this document for crude oil, refined products and lubricating oils. These values are shown in bold italics. Also shown In the table are the limits converted to their equivalent units (and, in the case of the densities, other base temperatures). TahIe2 shows defining limits of correction factors for light hydrocarbons (natural gas liquids and liquefied petroleum gases).
no later than two years after the publication date. An application for this purpose is defined as the point where the calculation is applied.
Once the revised standard is implemented In a particular application, the previous standard will no longer be used in that application.
It Is important to note that calculation results for crude oil, refined products or lubricating oils (but not NGL or LPG) based on Iso 91-1 and ISO 91-2 do not differ significantly from ISO 91. ISO 91 t also reflects changes that have been made to the calculation procedures leading to increased precision. The ranges of the volume correction factor tables referenced in ISO 91 have also been expanded (see AnnexA).
If an existing application for crude oil, refined products or lubricating oils (but not NGL or LPG) complies with ISO 911 or ISO 91-2, then It shall be considered in compliance with ISO 91. Once ISO 91 is implemented in a particular application, neither ISO 91-1 nor ISO 91-2 shall he used in that application.
however, the use of International Standards is voluntary and the decision on when to utilize a standard is an issue that is subject to the negotiations between the parties involved in the transaction.
NOTh Some ISO density standards might not have comparable discrimination levels to those speciIled in ISO 91.ISO-91-2017