EN ISO 6974-6:2005 PDF

Overview

EN ISO 6974-6:2005 (ISO 6974-6:2002) specifies a gas chromatographic (GC) method for the quantitative determination of hydrogen, helium, oxygen, nitrogen, carbon dioxide and hydrocarbons from C1 to C8 in natural gas using three capillary columns. Designed primarily for laboratory analysis, the standard defines applicable mole-fraction ranges and the conditions under which the stated precision applies. It is intended to be used together with ISO 6974‑1 and ISO 6974‑2 and can also be applied to many natural gas substitutes (with additional provisions such as a methanizer).

Keywords: EN ISO 6974-6:2005, ISO 6974-6, natural gas composition, gas chromatography, capillary columns, laboratory gas analysis

Key topics and technical requirements

• Measurement principle: Separation using three capillary columns arranged across two gas chromatographs, with:
  • a PLOT precolumn for CO2 and ethane separation,
  • a molecular-sieve PLOT column for permanent gases (He, H2, O2, N2, CH4),
  • a thick-film WCOT column (apolar) for C2–C8 hydrocarbons.
• Detectors: Thermal conductivity detector (TCD) for permanent gases and methane; flame ionization detector (FID) for C2–C8 hydrocarbons.
• Mole-fraction application ranges: Example ranges (precision valid within these):
  • Helium: 0.002–0.5% | Hydrogen: 0.001–0.5% | Oxygen: 0.007–5%
  • Nitrogen: 0.007–40% | Methane: 40–100% (method only applicable for methane in this range)
  • CO2: 0.001–10% and other minor species (CO, acetylene, ethene, C3–C8) have specified ranges.
• Performance & uncertainty: Ranges indicate where stated precision applies (not detection limits). Method includes procedures for operating conditions, performance requirements, calculation and reporting.
• Natural gas substitutes: Guidance provided; a methanizer may be required for certain analytes.

Applications and users

• Primary uses:
  • Determination of gas composition for custody transfer, quality control and reporting.
  • Calculation of derived properties: calorific value, relative density and Wobbe index.
• Who uses it:
  • Analytical laboratories in the natural gas industry
  • Transmission/distribution network operators and quality assurance teams
  • R&D and process control groups dealing with natural gas or gas substitutes
• Benefits: High separation power of capillary columns enables detection and quantification of low-level components and some substitute gas constituents.

Related standards

• ISO 6974-1: Guidelines for tailored analysis
• ISO 6974-2: Measuring-system characteristics and data processing statistics
• ISO 6974-3 to -5: Alternative GC methods for packed or different column configurations
• Normative references: ISO 6142, ISO 6143, ISO 7504

EN ISO 6974-6:2005 is a key standard for accurate, repeatable laboratory determination of natural gas composition using capillary-column gas chromatography.