ISO 15500-21:2023

Overview

ISO 15500-21:2023 is an international standard published by the International Organization for Standardization (ISO) that specifies tests and requirements for discharge line closures in compressed natural gas (CNG) fuel system components for road vehicles. Applicable to vehicles utilizing mono-fuel, bi-fuel, or dual-fuel CNG systems as defined in ISO 3833 and aligned with the natural gas quality requirements of ISO 15403-1, this standard ensures that discharge line closures meet rigorous safety, durability, and performance criteria.

Discharge line closures are essential for preventing contamination in relief lines while allowing the safe release of gas to the atmosphere during normal or emergency conditions. This standard is vital for manufacturers, automotive engineers, and regulatory bodies concerned with the safety and reliability of CNG-powered vehicles.

Key Topics

ISO 15500-21:2023 addresses several critical aspects of CNG discharge line closures for road vehicles:

• Scope of Application: Covers only discharge line closures, excluding LNG system components upstream of vaporizers, fuel containers, stationary gas engines, container-mounting hardware, electronic fuel management, and refuelling receptacles.
• Marking Requirements: Mandates clear identification of manufacturer data, model designation, serial numbers, applicable pressures, flow direction, type of fuel, and reference to this ISO standard for traceability.
• Construction and Assembly: Requires compliance with general provisions and test methods outlined in ISO 15500-1 and ISO 15500-2, with additional specifications relating to discharge line closure function.
• Test Methods and Performance Criteria: Specifies tests for hydrostatic strength, leakage, bending moment, corrosion and ageing resistance, vibration, vent tests, and water jet protection, ensuring robust performance in various operational conditions.
• Operational Endurance: Outlines repeat-use testing procedures, including temperature cycling and flow/pressurization endurance, to validate long-term reliability.
• Safety Requirements: Includes tests such as internal leakage vent and protection against high-pressure water jets to guarantee safe venting and resistance to environmental ingress.

Applications

CNG discharge line closures standardized under ISO 15500-21:2023 have practical applications in the design, production, and integration of CNG fuel systems for:

• Automotive Manufacturers: Ensuring the supply and installation of compliant discharge line closures for new CNG vehicles.
• CNG Vehicle Retrofit and Maintenance: Supporting safe conversion of conventional vehicles to CNG and providing clear criteria for maintenance and replacement of discharge line closures.
• Component Suppliers: Guiding the design and testing of discharge line closures intended for international automotive markets.
• Regulatory Bodies and Inspectors: Offering a unified set of requirements to evaluate vehicle safety and compliance with international standards.
• Fleet Operators: Helping in the procurement of vehicles and components that meet globally recognized safety and performance benchmarks for CNG fuel systems.

Implementing this standard enhances vehicle safety, promotes interoperability of CNG system components, and supports the broader adoption of natural gas vehicles by instilling confidence in performance and regulatory compliance.

Related Standards

For full compliance and context within the CNG fuel system component framework, ISO 15500-21:2023 should be used in conjunction with the following related standards:

• ISO 15500-1: Road vehicles - Compressed natural gas (CNG) fuel system components - Part 1: General requirements and definitions
• ISO 15500-2: Road vehicles - Compressed natural gas (CNG) fuel system components - Part 2: Performance and general test methods
• ISO 3833: Road vehicles - Types - Terms and definitions
• ISO 15403-1: Natural gas - Natural gas for use as a compressed fuel for vehicles - Part 1: Designation of the quality

These interlinked standards help ensure the reliability, compatibility, and safety of CNG fuel system components implemented globally in the automotive sector.