ISO 15403-1:2006

Overview

ISO 15403-1:2006 - Natural gas for use as a compressed fuel for vehicles - Part 1: Designation of the quality defines the international requirements and terminology for compressed natural gas (CNG) used in natural gas vehicles (NGVs). The standard helps manufacturers, vehicle and fuelling-station operators, and other stakeholders specify and verify fuel quality so that CNG systems operate safely, reliably and with satisfactory performance under all climate and driving conditions. It applies predominantly to on‑board gaseous CNG (typical storage pressures up to 20 000 kPa; maximum container pressure 25 000 kPa) and contains elements relevant to some stationary combustion engines. ISO 6976 is cited as a normative reference for calculating calorific values and Wobbe index.

Key topics and technical requirements

• Gas composition requirements - defines compositional attributes (methane-dominant mixtures, presence limits for ethane, propane, nitrogen, CO2, trace contaminants) relevant to fuel quality designation.
• Gas properties - calorific value (superior/inferior), density, relative density and related derived parameters used for metering and performance assessment.
• Driveability and performance - parameters such as Wobbe index and methane number (engine knock propensity) that affect combustion, drivability and engine protection.
• Protection of fuel systems - limits and guidance to avoid corrosion, poisoning, and liquid/solid deposition in fuel lines, storage and engine components.
• Test methods and sampling - recommended approaches for sampling CNG and tests needed to verify conformity to quality designation.
• Informative annexes - guidance on propane/butane content, Wobbe index ranges, engine knock, methane/octane relationships and water content considerations.

Practical applications and who uses it

• Vehicle manufacturers and engine designers use ISO 15403-1 to design fuel systems and calibrate engines for expected CNG qualities.
• Fleet operators and vehicle converters rely on the standard to specify acceptable fuel quality for procurement and conversions.
• Fuelling station operators and gas suppliers use the designation to ensure delivered CNG meets requirements and to configure treatment/blending processes.
• Regulators, testing laboratories and maintenance teams apply sampling and test-method guidance to verify conformity and investigate driveability or durability issues.
• Stationary engine operators may apply relevant clauses where CNG is used for power generation.

Related standards

• ISO 15403-2 (Technical Report) - specification and detailed composition data.
• ISO 6976 - calculation of calorific values, density and Wobbe index (normative reference).

Keywords: ISO 15403-1, CNG fuel quality, compressed natural gas, NGV fuel specification, Wobbe index, methane number, gas composition, natural gas vehicles.