Overview - EN ISO 7326:2016 (Rubber and plastics hoses, ozone resistance)
EN ISO 7326:2016 specifies standardized laboratory methods to assess the ozone resistance of outer covers of rubber and plastics hoses under static conditions. The document defines five test methods (depending on hose bore and construction), required conditioning and test-piece preparation, test cabinet and fixture requirements, and reporting essentials. The standard is intended to determine susceptibility to ozone cracking that can occur during storage or service in ozone-containing atmospheres.
Key topics and technical requirements
- Five test methods for outer covers:
- Method 1: test on the hose itself for bore ≤ 25 mm.
- Method 2: strip from hose wall for bore > 25 mm.
- Method 3: strip from cover for bore > 25 mm (remove reinforcement impressions).
- Method 4: hose sample wound around a cylinder (all bore sizes).
- Method 5: testing expandable hoses (e.g., textile‑reinforced) in the expanded state.
- Test conditions: default exposure to ozone concentration (50 ± 5) pphm at (40 ± 2) °C for 72 h (unless a product standard specifies otherwise).
- Test pieces and counts: three test pieces per evaluation; specified dimensions (e.g., 150 × 25 mm strip for Method 2; 25 mm width for cover strips in Method 3).
- Conditioning: no testing within 24 h of manufacture; mount and condition test pieces 48 h in substantially ozone‑free atmosphere at standard temperature.
- Apparatus: ozone cabinet with ozone generation and monitoring (per ISO 1431‑1), purpose‑made holders, cylinder or rods for specified methods; materials used inside the cabinet must not absorb or decompose ozone.
- Comparability note: results from different methods (e.g., Method 1 vs Method 2/3) may not be directly comparable; the product standard should specify which method to use.
- Alternative for hoses with fixed fittings: assess slabs/test sheets per ISO 1431‑1 when test pieces cannot be taken.
Applications - who uses EN ISO 7326:2016
- Hose manufacturers and compound formulators validating cover compounds for ozone resistance.
- Third‑party test laboratories performing conformity and warranty testing.
- Quality, R&D and materials engineers specifying hoses for outdoor, industrial or automotive applications where ozone exposure is a risk.
- Procurement and compliance teams requiring documented test evidence for product standards and certifications.
Related standards
- ISO 1431‑1: Resistance to ozone cracking - static and dynamic strain testing (referenced for ozone cabinet and alternative slab testing).
- ISO 23529: Conditioning and preparation of rubber test pieces.
- ISO 8330: Terms and definitions for rubber and plastics hoses and assemblies.
Keywords: EN ISO 7326:2016, ozone resistance, rubber and plastics hoses, static conditions, hose testing, ISO 1431-1, hose cover assessment, ozone cracking.
