ISO 15500-11:2015

Road vehicles - Compressed natural gas (CNG) fuel system components - Part 11: Gas/air mixer

ISO 15500-11:2015 specifies tests and requirements for the gas/air mixer, a compressed natural gas fuel system component intended for use on the types of motor vehicles defined in ISO 3833. ISO 15500-11:2015 is applicable to vehicles using natural gas in accordance with ISO 15403-1 (mono-fuel, bi-fuel, or dual-fuel applications). It is not applicable to the following: a) liquefied natural gas (LNG) fuel system components located upstream of, and including, the vaporizer; b) fuel containers; c) stationary gas engines; d) container mounting hardware; e) electronic fuel management; f) refuelling receptacles. NOTE 1 It is recognized that miscellaneous components not specifically covered herein can be examined to meet the criteria of this part of ISO 15500 and tested according to the appropriate functional tests. NOTE 2 All references to pressure in this part of ISO 15500 are to be considered gauge pressures unless otherwise specified. NOTE 3 This part of ISO 15500 is based upon a service pressure for natural gas as a fuel of 20 MPa (200 bar[1]) settled at 15 °C. Other service pressures can be accommodated by adjusting the pressure by the appropriate factor (ratio). For example, a 25 MPa (250 bar) service pressure system will require pressures to be multiplied by 1,25. [1] 1 bar = 0,1 MPa = 105 Pa; 1 MPa = 1 N/mm2.

Véhicules routiers — Composants des systèmes de combustible gaz naturel comprimé (GNC) — Partie 11: Mélangeur air/gaz

General Information

• Status: Published
• Publication Date: 29-Nov-2015
• ICS: 43.060.40 - Fuel systems
• Technical Committee: ISO/TC 22/SC 41 - Specific aspects for gaseous fuels
• Drafting Committee: ISO/TC 22/SC 41/WG 3 - Fuel system components and refuelling connector for vehicles propelled by gaseous fuel
• Current Stage: 9092 - International Standard to be revised
• Start Date: 14-Feb-2023
• Completion Date: 13-Dec-2025

Relations

• Revises: ISO 15500-11:2001 - Road vehicles - Compressed natural gas (CNG) fuel system components - Part 11: Gas/air mixer
• Effective Date: 20-Aug-2011

Overview

ISO 15500-11:2015 is an international standard developed by the International Organization for Standardization (ISO) that specifies the tests and requirements for gas/air mixers used in compressed natural gas (CNG) fuel system components for road vehicles. This part of the ISO 15500 series focuses specifically on the gas/air mixer, an essential component in motor vehicles that use natural gas as a fuel source. The standard applies to vehicles as defined in ISO 3833 and is relevant for mono-fuel, bi-fuel, or dual-fuel vehicles complying with ISO 15403-1. It excludes components related to liquefied natural gas (LNG) fuel systems, fuel containers, and other specified hardware.

Key Topics

• Scope and Applicability
  The standard covers gas/air mixers intended for CNG systems operating at a typical service pressure of 20 MPa (200 bar) at 15 °C, with provisions to adjust for other service pressures. It applies only to CNG fuel systems and excludes LNG systems, refuelling receptacles, electronic fuel management, and stationary engines.

• Marking Requirements
  Components must be clearly marked with traceable information such as manufacturer identification, model designation, working pressure, temperature range, and optional details like flow direction, fuel type, and certification symbols.

• Construction and Assembly
  Gas/air mixers must conform to the construction guidelines outlined in the general parts of ISO 15500 (Parts 1 and 2), ensuring durability and compatibility with other fuel system components.

• Testing Protocols
  ISO 15500-11:2015 defines several critical tests to ensure safety and reliability:

  • Hydrostatic Strength Test: Verifies the component withstands pressures at 4 times the recommended working pressure or 600 kPa, whichever is higher.
  • Leakage Test: Conducted across temperature ranges from -40 °C to +120 °C, verifying the mixer’s sealing integrity at pressures above working pressure.
  • Continued Operation Test: For mixers with moving parts, a durability test involving 100,000 cycles simulates long-term operational wear.
  • Corrosion Resistance Test: Ensures that materials used can withstand environmental exposure and maintain functionality.

• Types of Gas/Air Mixers Covered
  The document accommodates three mixer designs: positive and negative pressure venturi mixers (no moving parts) and variable orifice mixers.

Applications

ISO 15500-11:2015 provides critical guidance for manufacturers, designers, and testing laboratories involved in the production and certification of gas/air mixers in CNG fuel systems for road vehicles. Its practical applications include:

• Assurance of Fuel System Safety
  By specifying stringent testing methods and construction criteria, the standard helps prevent leaks, failures, and malfunctions related to gas/air mixing in CNG vehicles.

• Compatibility and Interchangeability
  Uniform marking and performance requirements enable seamless integration of gas/air mixers with other CNG fuel system components, contributing to vehicle reliability.

• Support for Clean Energy Vehicles
  Facilitates the adoption of natural gas as a cleaner alternative fuel by ensuring components meet international safety and performance benchmarks.

• Regulatory Compliance and Certification
  Enables manufacturers to demonstrate conformity with globally recognized standards, aiding market acceptance and regulatory approvals.

Related Standards

• ISO 15500 Series
  ISO 15500 comprises a comprehensive set of parts covering CNG fuel system components such as valves, injectors, regulators, and fuel lines. Part 11 complements these by focusing on gas/air mixers.

• ISO 3833
  Defines types of motor vehicles and relevant terminology for consistent classification.

• ISO 15403-1
  Specifies the quality and composition requirements for natural gas used as a compressed fuel, ensuring fuel consistency in accordance with which this standard applies.

• ISO 15500-1 and ISO 15500-2
  Provide general requirements, definitions, and performance test methods for CNG fuel system components, forming the foundation for Part 11 requirements.

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Keywords: ISO 15500-11:2015, gas/air mixer, compressed natural gas (CNG), fuel system components, CNG vehicle standards, natural gas fuel system, automotive CNG components, gas/air mixer testing, CNG safety standards, natural gas vehicle regulations.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 15500-11
Second edition
2015-12-01
Road vehicles — Compressed natural
gas (CNG) fuel system components —
Part 11:
Gas/air mixer
Véhicules routiers — Composants des systèmes de combustible gaz
naturel comprimé (GNC) —
Partie 11: Mélangeur air/gaz
Reference number
©
ISO 2015
© ISO 2015, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
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ii © ISO 2015 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Marking . 2
5 Construction and assembly . 2
6 Tests . 2
6.1 Applicability . 2
6.2 Hydrostatic strength . 3
6.3 Leakage . 3
6.4 Continued operation . 3
6.5 Corrosion resistance . 3
Bibliography . 4
Foreword
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The committee responsible for this document is ISO/TC 22, Road vehicles, Subcommittee SC 41, Specific
aspects for gaseous fuels.
This second edition cancels and replaces the first edition (ISO 15500-11:2001), which has been
technically revised.
ISO 15500 consists of the following parts, under the general title Road vehicles — Compressed natural
gas (CNG) fuel system components:
— Part 1: General requirements and definitions
— Part 2: Performance and general test methods
— Part 3: Check valve
— Part 4: Manual valve
— Part 5: Manual cylinder valve
— Part 6: Automatic valve
— Part 7: Gas injector
— Part 8: Pressure indicator
— Part 9: Pressure regulator
— Part 10: Gas-flow adjuster
— Part 11: Gas/air mixer
— Part 12: Pressure relief valve (PRV)
— Pa
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