ASTM D1250 standard guide for use of the petroleum measurement tables
5. Historical Background
5.1 The 1980 Petroleum Measurement Tables were based on data obtained using the International Practical Temperature Scale 1968 (IPTS-68). This has been superseded by the International Temperature Scale 1990 (ITS-90). API MPMS Chapter 11.1-2004/Adjunct to IP 200/04/Adjunct to ASTM D1250-04 (ADJD1250CD) takes this into account by correcting the input temperature values to an IPTS-68 basis before any other calculations are performed. Standard densities are also adjusted to take into account the small shifts in the associated standard temperatures.
5.2 The accepted value of the standard density of water at 60°F has changed slightly from the value used in the 1980 Petroleum Measurement Tables. This new water density only affects those tables based on relative density and API gravity, that is, the historical Tables 5, 6, 23 and 24. It also affects the intraconversion tables, API MPMS Chapter 11.1-1980 Volumes XI and XII/Adjunct to ASTM D1250-80 (ADJD125011).
5.3 In 1988 the IP produced implementation procedures for 20°C (Tables 59 A, B and D and 60 A, B and D) by extending the procedures used for the 15°C tables. This was in response to the needs of countries that use 20°C as their standard temperature. Although API never published these tables, they were adopted internationally as the reference document for International Standard ISO 91-2. ISO 91-2 complements ISO 91-1, the International Standard for temperatures of 60°F and 15°C that is based on Volume X of API MPMS Chapter 11.1-1980/Adjunct to IP 200/Adjunct to ASTM D1250-80 (ADJD125010). The 2004 revision to API MPMS Chapter 11.1/Adjunct to IP 200/Adjunct to ASTM D1250 (ADJD1250CD) incorporates the 20°C tables. The procedures adopted for the metric tables give results that are identical to those obtained using the 60°F tables. Furthermore, these procedures may be adapted to provide tables at any desired temperature base.
5.4 Implementation procedures for the lubricating oil tables first appeared in the IP's Petroleum Measurement Paper No 2: Guidelines for Users of the Petroleum Measurement Tables (API Standard 2540; IP 200; ANSI/ASTM D 1250), and later in their 20°C tables. The implementation procedures are now incorporated in API MPMS Chapter 11.1-2004/Adjunct to IP 200/04/Adjunct to ASTM D1250-04 (ADJD1250CD).
5.5 Rounding of density in metric tables changed from 0.5 kg/m3 to 0.1 kg/m3 to improve discrimination.
5.6 To satisfy industry needs, the tables have been extended to lower temperatures and higher densities (that is, lower API gravities).
5.7 Real-time density measurement using density meters has become more prevalent in the industry. These density measurements are often made at pressures greater than atmospheric. This pressure effect must be taken into account simultaneously with any temperature effect when determining the density at standard conditions. Hence, pressure and temperature corrections have been combined into one procedure.
5.8 Rounding and truncation of initial and intermediate values have been eliminated. Rounding will only be applied to the final VCF values.
5.9 The final VCF values will now be rounded to a consistent 5 decimal digits. API MPMS Chapter 11.1-2004/Adjunct to IP 200/04/Adjunct to ASTM D1250-04 (ADJD1250CD) also provides a mechanism to provide intermediate unrounded factors that, when combined, give the overall rounded CTPL (VCF).
5.10 The 1980 Petroleum Measurement Tables' implementation procedure used integer arithmetic in order to allow all existing computer equipment to achieve consistent results. This procedure now uses a double-precision floating-point math procedure.
5.11 Revised API MPMS Chapters 11.2.1 and 11.2.1M are now incorporated into API MPMS Chapter 11.1-2004. The 1984 versions of both will continue to be available on an historical basis.
5.12 Previous editions of the printed tables were based on density measurements made using a glass hydrometer. API MPMS Chapter 11.1-2004/Adjunct to IP 200/04/Adjunct to ASTM D1250-04 (ADJD1250CD) is based on the input of density values and no glass hydrometer corrections are applied. If density is measured using a glass hydrometer, hydrometer readings shall be corrected to density values before they are applied in the calculations.
6. Keywords
6.1 crude oil; density correction; lubricants; lubricating oils; Petroleum Measurement Tables; petroleum products; volume correction; volume correction factor
