ISO 91:2017 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 compressibihty. volumes arc 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 measurement, 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 oinUy by the American Society of Testing Materials (ASTM) in 1952 and the Institute of Petroleum (IP) (metric edition) In 19S3lJl. 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- 196611U1 (also designated ASTM 01250-56). A few amendments to ISO/H 91 resulted in the publication of a second edition in 19701Z1. ISO/R 91:1970/Amd 1:1975131 was published In 1975 for tables based on a relerence temperature ol 20 °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 at Petroleum Measurement Standards (MPMS) Chapter 11.1 (also designated API/Standard 2540. ASTM 01250-80 and lP 200/80) following the development of a new database by API in cooperation with the US NBS. This study Included the examination of 463 samples of crude oil and refined products. The crude oil samples represented 67 % of world production in 1974. The 1980 standard also constituted a ma)or conceptual departure from previous versions in the recognition of the use of computers in the petroleum industry. The actual standard represented by API MPMS Chapter 11.1-1980/ASTM 1)1250-SOuP 200/80 was
neither the hardcopy printed tables nor the set of equations used to represent the density data, but was an explicit implvnwntation procedure used to develop computer subroutines. The standardization of an implementation procedure implied the standardization ol the set of mathematical expressions, including calculational sequence and round-off procedures, used within the computer code. Adherence to the procedures given In API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80 was an attempt to ensure that all computers and computer codes meeting the stated specifications and restrictions would be able to produce identical results. Hence, the published implementation procedures were the primary standard, the distributed subroutines the secondary standard, and the published tables produced for convenience.
API MPMS Chapter 11.1-1980/ASTM D1250-80/IP 200/80 was referenced in Iso 91-1:1982141. Corrections to the 1980 standard were listed in ISO 91-1:1992151.
Computer implementation procedures developed by the IP for corrections to 20 °C were published in 1988. These implementation procedures were prepared as standard procedures to enable users to produce their own computer programmes either for the generation of 20 °C tables or for use an calculations without the generation of tables. IP Petroleum Measurement Paper No. 31111 was referenced In ISO 91-2:199 1lI, superseding Addendum 1:1975 to ISO/R 91.
Compressibility factors for hydrocarbons In the 0 to 100 API gravity range were developed in 1945 and published in 1960 as API/Standard 11011121. Appendix B, Table II. This table was superseded by API MPMS Chapters 11.2.11131 and 1 1.2 1M1141 published in 1984. API MPMS Chapter 11.21 M-1984 was adopted by ISOfTC 28 and published as ISO 9770:19891U1.
Compressibility factors for hydrocarbons in the 0,500 to 0,611 relative density range and 20 °F to 128 °F were published in 1984 as API MPMS Chapter 1 1,2.2L1.5J. A second edition of API MPMS Chapter 11.2.2
1 Scope
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 tinder pressure to the corresponding volumes at the equilibrium pressure for the measured temperature.
Table 1 shows the defining limits and their associated units of correction factors referenced in this document far crude oil, refined products and lubricating oils. These values are shown in bold Italics. Also shown in the table are the limits converted to theirequlvalent units (and. In the case of the densities. other base temperatures). Tablel shows defining limits of correction factors for light hydrocarbons (natural gas liquids and liquefied petroleum gases).
2 Normative references
The folIowng documents are referred to In the text In such a way that some or all of their content constitutes requirements of ISO 91. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (Including any amendments) applies.
API Manual of Petroleum Measurement Standards (MPMS) Chapter 11.1-2O04’)/Adunct to ASTM fl1250-042)/Adjunct to IP 200/04. Temperature and Pressure Volume Correction Factors for Generalized Crude Oils, Refined Products, and Lubricating Oils/Addendum 1-2007
API MPMS Chapter 11.2.2-1986, compressibility Factors for Hydrocarbons: 0.350-0.637 Relative Density (60 °F/60 °F) and -50 °F to 140 °F Metering Temperature/Errata June 1996
API MPMS Chapter 11.2.2 M- 1986, Compressibility Factors for hydrocarbons: 350-637 Kilograms per Cubic Metre Density (15 °C) and -46 °C w 60°C MeterIng Temperature
API MPMS Chapter 1 1.2.4-2007/GPA Technical Publication TP-27-2007, Temperature Correction for the Volume of NGL and LPG. Tables 23E, 24E, 53E, 54E 59E, and 60E
API MPMSChapter I 1.5) Part 1-2009/Adjunct to AS1’M D1250-08/Adjunct to IP 200/08, Density/Weight,’ Volume Intraconversion — Part 1: Conversions of API gravity at 60° F
API MPMS Chapter 1 1.5) Part 2-2009/Adjunct toASTM D1250-08/Adjunct to IP 200/08. Denslty/Weight/ Volume Intraconversio, — Part 2: Conversions for Relative Density (60/60° F)
API MPMS Chapter 1 t.S) Part 3-2009/Adjunct to ASTM D1250-08/Adjunct to lP 200/08. Density! Weight/ Volume Intraconversion — Port 3: Conve rslons for Absolute Density at 15° C
TP-27-2007. The implementation procedures describe how to calculate the CTL given an appropriatc density factor at basis temperature and an observed temperature, and calculate the appropriate density factor at basis temperature given a relative density at an observed temperature. The implementation procedures are presented in pairs by base temperature. First, the procedures for Tables 23E and 24E of API MIM.S Chapter 11.2.4-2007/CPA TP-27-2007 at a 60°F base temperature are given. The procedure for Table 23E makes use of the procedure described in Table 24E. thus Table 24E is presented firL These are followed by procedures for Table 54E and Table 53E at a base temperature of 15 °C, which themselves make use of the procedures in Table 23E and Table 24E; these in turn are followed by the procedures for Table 60E and Table 59E at a base temperature of 20 °C, which also make use of the procedures described in Table 23E and Table 24E.
To correct NGL and LPG volumes metered under pressure to the corresponding volumes under equilibrium pressure for the process temperature at the meter. reference shall be made to API MPMS Chapter 11.2.2-1986 (including Errata tune 1996) or API MPMS Chapter 1 1.2.2M-1986 or if outside of the density range of these standards, API MPMS Chapter 11.2.1-1984 or API MPMS Chapter 11.2.1 P41984.
These methods require a knowledge of the equilibrium bubble point pressure (vapour pressure) at the measured conditions. Uowever, the vapour pressure of the process liquid Is generally not measured. The vapour pressure can also be calculated from compositional information, but the composition Is not always measured for natural gas liquids (NGLs). Therefore, a correlation for the vapour pressure of NGLs based upon normally measured properties is required, and API MPMS Chapter 1 1.2.5-2007/GPA Technical Publication TP-15(ii can he used for this purpose. The procedure given in API MPMS Chapter 11.2.5/GPA TP-15 provides a simplified means of estimating equilibrium vapour pressures of various NGLS from a knowledge of the fluid’s relative densIty (60 °F/60 W) and process temperature. The intended application of this procedure is to provide the values of P (equilibrium vapour pressure) required to determine the pressure effect contributions to volume correction factors as specilied.
See Annex C for titles of petroleum measurement tables given in the 1980 editions of the API. ASTM, and lP volume correction factor standards, as well as a list ol the documents that have superseded these documents.