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The Norres Baggerman Group specifies pressure ratings for its hoses. There is no uniform ISO standard for the pressure ratings or test methods applicable to different types of hoses. Many manufacturers do not specify the test method used, nor do they explain how the specified overpressure and underpressure values are to be understood. This makes it very difficult or even impossible for users to compare the catalogue specifications of different suppliers.
This information page is intended to provide an overview of the various standardised test methods and relevant pressure values depending on the type of hose.
The relevant standards are as follows:
- DIN EN ISO 1402
Among other things, the standard specifies procedures for the hydrostatic testing of rubber and plastic hoses and hose assemblies. These include, for example, the change in length at a specified test pressure and the determination of the burst pressure, i.e. the pressure at which the hose or hose assembly bursts. - DIN 26057
The standard applies to spiral hoses made of thermoplastic polyurethane (TPU) with steel wire reinforcement for granulates and powdery substances. Among other things, it covers the procedure for testing overpressure and vacuum resistance. - DIN EN ISO 7751
The standard specifies the ratios of test and minimum burst pressure to maximum working pressure for rubber and plastic hoses and hose assemblies.
Pressure ratings and hose types
Testing AIRDUC®and PROTAPE® hoses made of TPU
The Norres Baggerman Group specifies overpressure and underpressure ratings for AIRDUC® and PROTAPE® TPU hoses in accordance with German standard DIN 26057 on the data sheets. In some cases, pressure ratings are also shown in brackets, indicating the overpressure at short-term loads with 25% and 50% elongation, as well as vacuum ratings for approximately 1 m long, axially fixed hose lengths close to collapse, as specified by other manufacturers.
Measurement of pressure resistance in accordance with DIN EN ISO 1402 and German DIN 26057:
- Test equipment: Pressure generator that generates a medium pressure of at least 6 bar. Test specimen, hose length with a free length of 1,000 mm between the hose connections/fittings.
- Conditioning: The test must be carried out at least 24 hours after the hose length has been manufactured. The test specimens must be conditioned at room temperature for at least three hours before the start of the test.
- Procedure: The test specimens are clamped into the test fixture by pushing the hose ends onto the connectors and securing them with suitable hose clamps without damaging the hose. The test specimen must be secured to the connector securely and tightly using the hose clamps. The free hose length between the connectors must be 1,000 mm. The test specimen must be stretched and aligned as straight as possible in the test fixture. The test temperature must correspond to room temperature. The pressure resistance is defined as the pressure that remains unchanged for one minute without the hose elongating by more than 10%. The corresponding pressure resistance values must be specified. The test requirement of a maximum elongation of 10% may mean that no values can be determined for type 1 hoses due to their design.
- Test results: The test result is the overpressure in bar measured at a hose elongation of 10%. In addition, we sometimes show pressure ratings in brackets for short-term loads with 25 to 50% hose elongation, as some other manufacturers do, but we advise against using the products under these conditions.
Measurement of vacuum resistance in accordance with German DIN 26057:
- Test equipment: Vacuum pump for test medium air, with which an absolute pressure of 0.2 bar (−0.8 bar vacuum) is achieved with uniform evacuation, test specimen with a hose length which has a free length of 1,000 mm between the hose connections.
- Conditioning: The test must be carried out at least 24 hours after the hose length has been manufactured. The test specimens must be conditioned at room temperature for at least three hours before the start of the test.
- Procedure: The test specimen is installed in a test device by sliding the hose onto the test connection and securing it with hose clamps without damaging the hose. The test specimen must be stretched and aligned as straight as possible in the test device. The outer diameter of the test connection corresponds to the inner diameter of the test specimen and is designed so that the test medium cannot escape during the test. One test connection is rigidly connected to the test device and cannot be rotated. The other test connection is rotatable, allowing the test specimen to rotate during the test. The slide is mounted so that it moves smoothly, allowing the test specimen to change length during the test. The vacuum resistance is defined as the pressure that remains unchanged for one minute without the hose shortening by more than 10%. The corresponding vacuum resistance values must be specified. The test requirement of a maximum 10% reduction may mean that no values can be determined for type 1 hoses due to their design.
- Test results: The test result is the vacuum in bar measured with a 10% reduction in hose length. In addition, we sometimes show vacuum ratings in brackets for 1 m straight and axially fixed hose lengths close to collapse, as some other manufacturers do, but we advise against using the products under these conditions. Due to their design, the 10% hose shortening cannot be measured for some PROTAPE® hoses with wall thicknesses of 0.4 to 0.6 mm. In these cases, we specify recommended operating limits.
Testing rubber hoses
The Norres Baggerman Group tests rubber hoses in accordance with DIN EN ISO 7751 and DIN EN ISO 1402:
| Application | Ratio of test pressure to maximum working pressure | Ratio of burst pressure to maximum working pressure |
|---|---|---|
| Hose for water, all other liquids or suspended solids in liquids or air | 1.5 | 3.0 |
| Hose for steam | 5.0 | 10.0 |
The working pressure can be found on the hose (standard marking). For all other hose types, the pressure specifications are recommended operating limits at 20°C.
Do you have any questions about pressure values and the associated measurements? The Norres Baggerman Group's team of experts will be happy to help you!
Engineering modifications subject to change.