Overview
ISO 11425:2018 specifies performance requirements for rubber hoses and hose assemblies used in automobile power‑steering systems. The standard covers five hose types that differ by pressure rating and volumetric expansion, and applies to operation with fluids from −40 °C to +135 °C. ISO 11425 is performance‑based (tests and criteria) and does not mandate specific materials or detailed construction, allowing for technological development and innovation.
Key topics and technical requirements
- Hose types:
- Type 1 - low‑pressure hydraulic return hoses
- Type 2 - medium‑pressure, low volumetric expansion
- Type 3 - medium‑pressure, medium volumetric expansion
- Type 4 - medium‑pressure, high volumetric expansion (includes cold‑start tests)
- Type 5 - high‑pressure, low volumetric expansion
- Pressure and burst requirements: design working pressures range by type (e.g., Type 5 design pressures up to ~15.5 MPa) and minimum burst pressures up to ~62 MPa for some sizes (see Table 2 in ISO 11425:2018).
- Impulse resistance: hoses must withstand a pulse test (ISO 6803) - typically a minimum of 225 000 cycles at elevated temperatures without rupture or excessive leakage.
- Volumetric expansion: specified at 9 MPa for type‑3 and type‑4 hoses (type‑4 example range ~26 to 55 cm³/m at 9 MPa; type‑3 is lower - see the standard for exact values).
- Mechanical and environmental tests: low‑temperature flexibility (−40 °C), adhesion (ISO 8033), ozone resistance (ISO 7326), contamination limits (max particle size and mass), corrosion resistance of fittings (salt spray ISO 9227), proof and burst pressure tests (ISO 1402).
- Marking: each hose must be indelibly marked with manufacturer ID, “ISO 11425:2018” and year, hose type, inside diameter (mm), manufacture date (quarter + year), and design working pressure. Example format: XXX /ISO 11425:2018/3/9,5/4Q18/15,5.
Applications and users
ISO 11425:2018 is intended for:
- Automotive OEMs (power‑steering system designers and specifiers)
- Hose and hose‑assembly manufacturers and suppliers
- Quality and test laboratories performing hydraulic and environmental testing
- Aftermarket parts manufacturers and certification bodies
Use cases include specification of hose assemblies for rack‑and‑pinion and other hydraulic power‑steering circuits, production acceptance testing, and supplier qualification.
Related standards
ISO 11425 references several test standards; key related documents include:
For exact numeric limits, test procedures and full tables, consult the official ISO 11425:2018 publication.