GOST 31371.2-2020 PDF

Full title and description

GOST 31371.2-2020 — Natural gas. Determination of composition by gas chromatography method with evaluation of uncertainty. Part 2. Uncertainty calculations. This part establishes procedures for calculating the uncertainty of the molar fraction of each natural gas component determined by gas chromatography as defined in the companion part (Part 1).

Abstract

This standard specifies the method for computing measurement uncertainty (including combined and expanded uncertainties) associated with molar fractions of natural gas components determined by gas chromatography. It is intended to be used together with the analytical and procedural guidance given in the related parts of the GOST 31371 series and is aligned with ISO 6974‑2:2012 principles for uncertainty calculations.

General information

• Status: Active (current national/interstate standard).
• Publication date: 1 July 2021 (designated GOST 31371.2‑2020; entry into national registers took place later in some jurisdictions).
• Publisher: Interstate / national standards bodies (GOST series — developed under the interstate technical committee MTK 52 with participation of industry organizations and institutes, and published as an interstate/national GOST).
• ICS / categories: 75.060 (Natural gas and manufactured gas).
• Edition / version: 2020 (GOST 31371.2‑2020 — supersedes the 2008 edition).
• Number of pages: ≈24 pages (commercial copies and registries list 23–28 pages depending on formatting; a 24‑page electronic PDF is commonly referenced).

Scope

The standard covers the mathematical and procedural framework for evaluating uncertainty components that affect the determination of component molar fractions by gas chromatography. It addresses sources of uncertainty in the measurement system, propagation of uncertainty through chromatographic quantitation and calibration, computation of combined and expanded uncertainties, and requirements for reporting uncertainty together with analytical results. It is intended to be applied where results from GOST 31371.1 (and related measurement procedures) are used for trade, regulatory reporting or technical control.

Key topics and requirements

• Definition and classification of uncertainty components (type A and type B) relevant to gas‑chromatographic analysis of natural gas.
• Characterisation of the measurement system (repeatability, reproducibility, calibration, detector response stability) and how each contributes to overall uncertainty.
• Formulas and procedures for combining uncertainty contributions and for calculating expanded uncertainty (typically with a stated coverage factor).
• Guidance on uncertainty propagation for derived quantities such as molar fractions and summed fractions (including treatment of correlations between components).
• Requirements for documenting and reporting uncertainty alongside analytical results to support traceability and comparability.
• Alignment and equivalence with ISO 6974‑2:2012 methodology for uncertainty calculations in gas‑chromatographic composition analysis.

Typical use and users

Primary users are analytical laboratories (commercial and research), gas producers and suppliers, metrology and certification bodies, pipeline and distribution operators, and regulatory authorities. The standard is used to: implement laboratory quality systems, quantify measurement confidence for trade and custody transfer, prepare conformity and compliance reports, and support interlaboratory comparisons and method validation.

Related standards

GOST 31371.2‑2020 is part of the GOST 31371 series on natural gas composition by gas chromatography and is associated with other parts such as GOST 31371.1 (analytical procedures), GOST 31371.5 (isothermal methods for certain components), and GOST 31371.7 (measurement procedures for component molar fractions). The standard is also aligned with the ISO 6974 series (notably ISO 6974‑2:2012).

Keywords

Natural gas, gas chromatography, composition, molar fraction, uncertainty, measurement uncertainty, expanded uncertainty, calibration, measurement system, GOST 31371, ISO 6974.

FAQ

Q: What is this standard?

A: GOST 31371.2‑2020 is the second part of the GOST 31371 series that specifies how to calculate the measurement uncertainty associated with determining natural gas composition by gas chromatography.

Q: What does it cover?

A: It covers identification of uncertainty sources, statistical treatment of measurement data, formulas for combined and expanded uncertainty, treatment of correlations between components, and reporting requirements for analytical results (molar fractions). It is intended for use alongside the procedural parts of the series.

Q: Who typically uses it?

A: Analytical laboratories, gas suppliers and transporters, regulatory agencies, metrology institutes, and organisations involved in custody transfer, quality control, and method validation for natural gas composition.

Q: Is it current or superseded?

A: The 2020 edition (published/entered into force in 2021 in many registries) is the current version that supersedes the 2008 edition (GOST 31371.2‑2008). The standard is listed as active in commercial and registry listings.

Q: Is it part of a series?

A: Yes — it is Part 2 of the GOST 31371 series on determination of natural gas composition by gas chromatography with uncertainty estimation. Other parts cover measurement procedures, component‑specific methods, and reporting/measuring instructions. The series generally follows the structure and principles of the ISO 6974 family.

Q: What are the key keywords?

A: Natural gas, gas chromatography, measurement uncertainty, molar fraction, expanded uncertainty, calibration, GOST 31371, ISO 6974.