Plastic hoses and hose assemblies – Textile reinforced types for hydraulic applications – Specification (ISO 3949:2020); German version EN ISO 3949:2020
1Key Takeaways
This document specifies requirements for three types of textile-reinforced thermoplastic hoses and hose assemblies with nominal diameters from 3.2 to 25 mm. Depending on the electrical conductivity requirements, each type is divided into two classes. They are suitable for use with: ——the oil-based hydraulic fluids HH,…
2Expert Interpretation
This in-depth analysis of the DIN EN ISO 3949:2020 standard covers the technical requirements, performance test methods, classification system, and quality control points for textile-reinforced thermoplastic hydraulic hoses. It also provides detailed analysis of key parameters such as pressure ratings, dimensional tolerances, and fluid compatibility for the three hose types R7, R8, and R18, providing professional guidance for hose selection in hydraulic systems.
Standard Overview and Technical Evolution
DIN EN ISO 3949:2020 is the international standard specification for textile-reinforced thermoplastic hoses and hose assemblies for hydraulic systems, replacing the 2018 version. The standard was jointly developed by ISO/TC 45, Rubber and rubber products, and CEN/TC 218, Rubber and plastic hoses and hose assemblies. The German version was published by the DIN Technical Standards Committee for Elastomers (NET).
The main technical changes in this revision include:
- In clause 7.9.3, the volume change rate of the inner and outer layers in the water-based liquid resistance test is adjusted from 0% to +25% to 15% to +35%
- In clause 7.9.4, the volume change rate of the inner and outer layers in the water resistance test is adjusted from 10% to +25% to 15% to +35%
- Editorial revision of the standard text
Scope of application and classification system
This standard applies to three types of textile reinforced thermoplastic hoses with a nominal inner diameter of 3.2 to 25 mm. Each type is divided into two grades according to the conductivity requirements:
| Hose type | Maximum working pressure characteristics | Grade classification | Applicable fluid media |
|---|---|---|---|
| R7 Type | One or more reinforcement layers | Grade 1: No electrical requirements Grade 2: Non-conductive type | • HH, HL, HM, HR, HV oil-based hydraulic fluids as specified in ISO 6743-4 (-40°C to +93°C) • HFC, HFAE, HFAS, HFB water-based fluids (0°C to +60°C) • Water (0°C to +60°C) |
| R8 Type | One or more reinforcement layers, higher working pressure | Same as above | |
| R18 Type | Designed based on 21.0MPa working pressure | Same as above |
Application Case: In hydraulic systems of construction machinery, R8-type Class 2 non-conductive hose is often used to connect high-pressure pump stations and actuators. Its textile reinforcement structure can effectively withstand pressure pulses, while its non-conductive nature avoids the risk of static electricity accumulation.
Material Structure and Manufacturing Requirements
The hose must consist of a seamless thermoplastic inner layer resistant to hydraulic fluids, a suitable textile yarn reinforcement layer, and an outer layer resistant to hydraulic fluids, water, and weathering. The outer layer of the Class 2 hose must not have pinholes and must be orange (RAL 2004).
Hose assemblies can only be manufactured using hose connectors that meet the requirements of 7.1, 7.4, and 7.5. Class 2 hoses must also meet the electrical requirements of 7.8.
Dimensions and Tolerance Requirements
Diameter Tolerance
When measured in accordance with ISO 4671, the hose diameter must conform to the values specified in Table 1:
| Nominal Diameter | Inside Diameter (mm) | Maximum Outside Diameter (mm) | ||||||
|---|---|---|---|---|---|---|---|---|
| Minimum Value | Maximum Value | Type R7 | Type R8 | Type R18 | ||||
| 3.2 | 3.4 | 4.0 | 9.5 | 10.5 | 9.5 | 10.5 | 9.5 | 10.5 |
| 5 | 4.6 | 5.4 | 11.4 | 14.6 | 11.4 | 14.6 | 10.8 | 14.6 |
| 6.3 | 6.2 | 7.0 | 13.7 | 16.8 | 13.7 | 16.8 | 13.5 | 16.8 |
| 8 | 7.7 | 8.5 | 15.6 | 18.6 | 15.6 | 18.6 | 16.6 | 18.6 |
| 10 | 9.3 | 10.3 | 18.4 | 20.3 | 18.4 | 20.3 | 18.4 | 1.0|
| ＞19 | 1.3 | |||||||
Physical Property Requirements
Hydraulic performance requirements
Hoses and hose assemblies shall not leak when tested in accordance with ISO 1402 at the relevant test pressure. 84.0
Length Variation
When tested in accordance with ISO 1402, the hose shall not vary in length by more than ±3% at Maximum Working Pressure.
Pulse resistance
Pressure pulse test must comply with ISO 6803, test fluid temperature 93°C:
- R7 hose: withstand at least 150,000 pulse cycles at a pulse pressure of 125% of the maximum working pressure
- R8/R18 hose: withstand at least 200,000 pulse cycles at a pulse pressure of 133% of the maximum working pressure
Fluid compatibility test
Tested using molded plates of inner and outer material with a thickness of at least 2mm:
| Test type | Test conditions | Volume change rate requirement |
|---|---|---|
| Oil resistance | Immersed in No. 3 oil for 72±2h, (100±3)°C | 15%～+35% |
| Resistant to water-based liquids | A mixture of equal volumes of 1,2-ethylene glycol and distilled water, 168±2h, (70±1)°C | 15%～+35% |
| Water resistance | Immersed in distilled water for 168±2h, (70±1)°C | 15%～+35% |
Test frequency and quality control
Type test and piece test
Type testing is necessary to prove that hoses or hose assemblies manufactured with specific structures, specific processes, and specific materials comply with all the requirements of this standard. It must be repeated every 5 years or when the manufacturing process/material is changed.
Piece-by-piece testing is a test that must be performed on each finished hose before delivery, including:
- Appearance inspection (internal and external surfaces)
- Inner diameter measurement
- Outer diameter measurement
- Concentricity measurement
- Test pressure test
Manufacturing process test
It is recommended to conduct a manufacturing process test every 3,000 meters of production or every 12 months (whichever comes first), including a bursting pressure test, length change test, etc.
Identification and marking requirements
Hose marking
The hose must be marked with the following information at least, and the marking shall be repeated at least every 760mm:
- Manufacturer’s name or trademark
- Nominal number of this standard ISO 3949
- Type and grade (e.g. R7-1)
- Grade 2 hose marked with "NON-CONDUCTIVE"
- Nominal diameter
- Maximum working pressure (MPa and bar)
- Quarter and year of manufacturing (e.g. 2Q21)
Example: XXX/ISO 3949/R7-1/16/10.5 MPa (105 bar)/2Q21
Hose assembly marking
Hose assemblies manufactured using hoses conforming to this standard must be marked in accordance with ISO 17165-1 manufactured and marked.
Implementation Recommendations and Best Practices
Selection Guide
Select the appropriate hose type according to the hydraulic system working pressure, media type and environmental conditions:
- R7 type: Suitable for medium pressure applications, cost-effective
- R8 type: Suitable for high-pressure systems, excellent pulse resistance
- R18 type: Designed for 21.0MPa working pressure, highest reliability
Installation and Maintenance
It is recommended to follow the selection, storage, use and maintenance guidelines in ISO 8331:
- Avoid excessive bending during installation and ensure that the minimum bend radius meets the requirements of Table 6
- Regularly inspect the appearance of the hose and replace it promptly if any abnormalities such as cracks or expansion are found
- Store away from direct sunlight and extreme temperatures
Key Quality Control Points
Manufacturers should establish a comprehensive quality control system, focusing on:
- Raw material inspection, especially the fluid compatibility of the inner and outer layer materials
- Production process control to ensure uniformity and bonding quality of the reinforcement layer
- Finished product inspection, strictly implementing piece-by-piece testing requirements
- Labeling management to ensure traceability
Technological Trends: As hydraulic systems evolve toward higher pressures and intelligent systems, textile-reinforced hoses are moving toward higher working pressures, improved flexibility, and longer service lives. The use of new materials, such as specialty thermoplastic elastomers, is expanding the temperature range and chemical compatibility of hoses.
Conformity Assessment and Certification
Manufacturers should establish a comprehensive test record system, including type test reports, piece-by-piece test records, and manufacturing process test data. Test certificates should be provided to customers upon request, demonstrating compliance with all requirements of DIN EN ISO 3949:2020.
Certification bodies typically audit manufacturers' quality assurance systems, test equipment, and personnel qualifications to ensure ongoing compliance with standards. Regular surveillance audits are necessary to maintain the validity of certification.