ISO 6578-2017 PDF

Full title and description

St ISO 6578-2017 — Refrigerated hydrocarbon liquids — Static measurement — Calculation procedure. Specifies calculation methods to convert volumes of liquefied petroleum gas (LPG) and liquefied natural gas (LNG) measured under static tank conditions to equivalent volumes at standard conditions (15 °C and 101,325 kPa absolute), and to convert those quantities to mass or energy (calorific content).

Abstract

ISO 6578:2017 (second edition) provides the calculation procedure for adjusting the measured volume of refrigerated hydrocarbon liquids (LPG and LNG) to standard reference conditions, including corrections for vapour phase, conversion to mass and calorific content, and procedures for computing liquid density from composition. It applies to static (tank) measurement and does not cover pressurized gas measurement.

General information

• Status: Withdrawn (second edition ISO 6578:2017 — replaced by a later edition).
• Publication date: October 2017 (second edition, published 13 October 2017).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 75.180.30 (Volumetric equipment and measurements).
• Edition / version: Edition 2 (2017).
• Number of pages: 25 (second edition).

Scope

Applies to quantities of refrigerated hydrocarbon liquids (LPG and LNG) that are stored in, or transferred to/from, tanks and measured under static storage conditions. The standard defines the calculation workflow to convert measured volumes at measurement conditions to equivalent volumes at the standard reference condition (15 °C and 101,325 kPa absolute), and to calculate equivalent mass and calorific content. Calculation of pressurized gases is excluded.

Key topics and requirements

• Procedure to correct measured liquid volume to standard conditions (15 °C, 101 325 kPa).
• Methods to calculate mass of liquid phase and corrections for vapour phase and buoyancy.
• Calculation of calorific (energy) content from composition and conversion between volumetric and mass bases.
• Algorithms to compute liquid density from composition for LPG and LNG mixtures.
• Normative and informative annexes providing component molar volumes, correction factors, and gross calorific values for common components.

Typical use and users

Used by custody transfer and storage operators, LNG/LPG terminal engineers, metrology and calibration laboratories, pipeline and tank gauging system vendors, energy accountants, and software developers implementing quantity-conversion and custody-transfer systems. The standard is applied where static tank measurement and accurate conversion to mass or energy basis are required for commercial or regulatory purposes.

Related standards

Relevant standards and documents include earlier and later editions of ISO 6578 (1991 and the 2025 edition that replaces the 2017 edition), and other gas-property and calculation standards such as ISO 6976 (calculation methods for calorific values and related physical property data). The 2025 revision explicitly aligns calculation data with ISO 6976:2016.

Keywords

refrigerated hydrocarbon liquids; LPG; LNG; static measurement; tank gauging; volume correction; density from composition; mass conversion; calorific content; custody transfer.

FAQ

Q: What is this standard?

A: ISO 6578:2017 is the second-edition International Standard titled "Refrigerated hydrocarbon liquids — Static measurement — Calculation procedure," which specifies calculation methods for converting measured LPG and LNG volumes in static tanks to standard conditions and to mass or energy.

Q: What does it cover?

A: It covers the calculation workflow for volume correction to 15 °C and 101 325 kPa absolute, mass determination (including vapour corrections and buoyancy), conversion to calorific (energy) content, and density calculations from mixture composition for LPG and LNG. It excludes pressurized gas calculations.

Q: Who typically uses it?

A: Terminal operators, custody-transfer specialists, metrology labs, engineers responsible for tank gauging and LNG/LPG measurement, and software vendors implementing commercial quantity-conversion and billing systems.

Q: Is it current or superseded?

A: The 2017 edition has been withdrawn and superseded by ISO 6578:2025 (third edition, published in 2025); users should adopt the 2025 edition for current, published technical requirements.

Q: Is it part of a series?

A: Yes — ISO 6578 has previous and subsequent editions (ISO 6578:1991, ISO 6578:2017, and ISO 6578:2025). It is part of the suite of standards addressing measurement and calculation of hydrocarbon gas and liquid properties and custody-transfer practices (work by ISO/TC 28/SC 5).

Q: What are the key keywords?

A: Refrigerated hydrocarbon liquids; LPG; LNG; static measurement; tank gauging; volume-to-standard conversion; density from composition; calorific content; custody transfer.