Overview - ISO 18955:2025 (Railway rubber diaphragms)
ISO 18955:2025 defines the characteristics, inspection and test methods for rubber diaphragms used in pneumatic suspension springs for railway applications. It applies to diaphragms (inflated with air) fitted on railway and similar vehicles running on dedicated track systems. The standard covers diaphragm construction (elastomer, textile fabrics, metallic beads), functional and geometrical characteristics, environmental and operating conditions, and procedures for product approval and qualification. It does not cover other air-spring system components (air reservoirs, piping, levelling systems, frames, emergency or series springs), which can nevertheless influence diaphragm performance.
Key topics and technical requirements
- Materials and construction: Requirements for elastomers, reinforcement plies, metallic beads and adherence between plies.
- Resistance to operating conditions: Tests and criteria for low temperature performance, ozone resistance, cleaning agents, abrasion and fire behaviour.
- Physical performance: Pressure resistance, airtightness, fatigue resistance and burst resistance.
- Functional characteristics: Stiffness parameters, the relationship between internal pressure and axial static force, and axial isobar characteristics.
- Geometrical and dimensional checks: Mass, space envelope, overall dimensions and appearance (new and under extreme deformation).
- Inspection and test methods: Defined test conditions, instrumentation, specimen preparation, and specific test procedures for each characteristic.
- Quality and conformity: Marking, traceability, supplier production plan qualification, approval and product qualification procedures, and ongoing inspection/surveillance.
- Annexes: Informative examples (types of diaphragm, fatigue test programmes) and a normative qualification procedure.
Practical applications and value
- Ensures reliable, safe performance of air suspension diaphragms in rail vehicles by providing standardized acceptance and verification methods.
- Helps designers, manufacturers, suppliers and procurement teams specify diaphragms with consistent mechanical, environmental and dimensional properties.
- Supports maintenance and quality assurance programs by defining tests for fatigue, airtightness and burst resistance, and by specifying traceability and marking requirements.
- Useful in lifecycle planning where resistance to ozone, cleaners, abrasion and temperature extremes affects reliability and replacement intervals.
Who uses ISO 18955:2025
- Railway vehicle manufacturers and designers (OEMs)
- Suspension and air-spring component manufacturers and suppliers
- Quality, testing and certification laboratories
- Procurement teams and maintenance engineers specifying replacement diaphragms
Related standards
- Standards for general railway suspension systems, air-spring assemblies and test methods (refer to normative references in ISO 18955 for specific cross-references).