Overview
EN ISO 8973:1999/A1:2020 is Amendment 1 to ISO 8973:1997, adopted by CEN in April 2020. It updates the international calculation method for density and vapour (vapor) pressure of liquefied petroleum gases (LPG). The amendment clarifies references, corrects wording in the calculation clause, and adjusts an essential density factor used for ethane in the standard’s annex table. This document is relevant for suppliers, laboratories and engineers who perform LPG property calculations for design, safety, quality control and trade.
Key topics and technical requirements
- Scope: Calculation method for LPG density and vapour pressure (as per ISO 8973 methodology); amendment only (no change to main standard structure).
- Reference updates:
- Replaces the cited reference for gas chromatography analysis with ISO 7941 (no year specified in the amendment text).
- Moves ISO 6578:1991 (distillation characteristics) to the bibliography.
- Clause change (6.3.2):
- Clarifies the instruction to “Calculate the absolute vapour pressure of the LPG, p in kilopascals at 37.8 °C, 40 °C, 50 °C or 70 °C as follows:” - improving wording to explicitly state absolute vapour pressure and units (kPa).
- Annex A correction:
- Updates the density factor for ethane in Table A.1 from 375.76 to 359.78, a numerical correction that affects density computations for LPG mixtures containing ethane.
- Units and temperatures: The amendment reinforces calculation at standardized temperatures commonly used in LPG property reporting (37.8 °C, 40 °C, 50 °C, 70 °C).
Applications and users
Who uses EN ISO 8973:1999/A1:2020:
- Petroleum and LPG producers calculating product density and vapour pressure for specification sheets.
- Analytical laboratories performing gas chromatography and property calculations for quality control and certification.
- Process, storage and transport engineers designing LPG tanks, pipelines and safety systems where accurate vapour pressure and density are required.
- Regulators and metrology labs for compliance testing, custody transfer calculations and safety assessments.
Practical uses include density-based mass/volume conversions, pressure-temperature safety margins, tank design calculations and product grading.
Related standards
- ISO 8973:1997 - original calculation method for LPG density and vapour pressure (this amendment).
- ISO 7941 - Commercial propane and butane - Analysis by gas chromatography (referenced).
- ISO 6578:1991 - Petroleum products - Determination of distillation characteristics (moved to bibliography).
Keywords: EN ISO 8973:1999/A1:2020, liquefied petroleum gases, LPG density, vapor pressure calculation, ISO 8973 amendment, ethane density factor.