Overview
EN ISO 5175-2:2017 (Corrected version 2019-01) - published by CEN - specifies general requirements and type tests for safety devices used with fuel gases and oxygen or compressed air in gas welding equipment that do not incorporate a flame (flashback) arrestor. The standard applies to devices installed downstream of manifold, cylinder and/or pipeline outlet regulators and upstream of blowpipes for welding, cutting and allied processes. It does not prescribe installation location in the gas system and is not applicable to devices that include a flame arrestor (see ISO 5175‑1).
Keywords: EN ISO 5175-2:2017, gas welding equipment, safety devices, flashback arrestor, CEN.
Key topics and technical requirements
- Scope and definitions: terminology aligned with ISO 15296 (vocabulary) and definitions for non-return valves, pressure relief valves, excess-flow cut-off valves and multifunctional safety devices.
- Design and materials:
- Threaded connections up to G1 per EN 560; quick-release couplings per ISO 7289.
- Materials to conform to ISO 9539.
- Required safety functions:
- Non-return (check) valves to prevent reverse gas flow.
- Pressure relief valves to vent at predetermined overpressure and re-seal.
- Excess-flow cut-off valves to stop flow when a preset flow is exceeded.
- Multifunctional devices combining two or more functions.
- Performance and testing:
- Type tests for gas tightness, pressure resistance, valve function tests (non-return, relief, excess-flow), and internal leakage where applicable.
- Test methods, measurement accuracy and recommended test gases are specified.
- Documentation and marking:
- Manufacturer’s instructions and marking requirements are included to ensure safe selection and use.
- Informative annexes: gas flow measurement (Annex A) and third-party testing guidance (Annex B).
Keywords: gas tightness test, pressure resistance, excess flow cut-off, non-return valve test, type testing.
Applications and users
- Manufacturers of gas welding safety devices and multifunctional units - for product design, type testing and compliance.
- Test laboratories and certification bodies - for conducting required performance and safety tests.
- Welding equipment suppliers and OEMs - to specify compliant safety devices for regulators, manifolds and blowpipes.
- Safety engineers, procurement and maintenance teams - to verify device suitability, marking and manufacturer instructions for welding, cutting and allied processes.
- Regulators and standards committees - for harmonised safety requirements across CEN member countries.
Keywords: welding safety, equipment testing, regulator downstream devices.
Related standards
This standard is essential where gas safety device performance and consistent testing are required but does not substitute for installation rules or device placement in gas systems.
