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Pressure Ratings

The pressure and vacuum testing of thermoplastic hoses varies from country to country and from manufacturer to manufacturer. There is no international ISO standard for most of those products and the general rule of rubber hoses that working pressure is 1/3 of bursting pressure could not be applied to thermoplastic materials.

Most manufacturers do not name their testing methods or how stated pressure and vacuum figures should be understood. For end users it is difficult or impossible to compare catalogue data of different suppliers.

Since 2016 Germany has the national DIN 26057 standard which is binding for testing of “Spiralled hoses made of thermoplastic polyurethane (TPU) with steel wire reinforcement for granulated and powdered materials”.

NORRES is stating pressure and vacuum figures for those AIRDUC® and PROTAPE® hoses according to this German DIN 26057. Additionally we show sometimes in brackets pressure figures for special operational conditions.

Test of pressure resistance according to ISO 1402 and German DIN 26057:

  • Test device: A pump for test medium water which generates a media pressure of at least 6 bar = 90 psi. Test specimen, hose length, which has a free length of 1 m = 3 ft between the hose spigots / fittings.
  • Conditioning: The test may be carried out at the earliest 24 hours after the hose length has been produced. The test specimens must be conditioned at least three hours before the start of testing at room temperature.
  • Procedure: The test specimens are clamped into the test fixture by pushing the hose ends onto the nozzles and fixing them by means of suitable hose clips without damaging the hose. By means of the hose clamps, the test specimen must be securely and tightly attached to the neck. The free hose length between the nozzles must be 1 m = 3 ft. The test specimen must be stretched and aligned as straight as possible in the test fixture. The test temperature must correspond to the room temperature. The compressive strength is the pressure which remains unchanged for one minute, at which an elongation of the hose of 10 % is not exceeded. The corresponding compressive strength values shall be indicated. The test requirement is a maximum of 10 % elongation can mean that no values can be determined for hoses with wall thickness up to 0,6 mm = 0.025 inch.
  • Test results: As a test result, the pressure is measured at a hose elongation of 10 %. Additionally we show in brackets pressure figures for short-term stress with 25 to 50 % elongation as some other manufacturers but we do not advise to operate the product under these conditions.

Test of vacuum resistance according to German DIN 26057:

  • Test device: Vacuum pump for test medium air, which generates an absolute pressure of at least 0,2 bar = 2.9 psi = 5.9 inHG (-0,8 bar = 11.6 psi = 23.6 inHG vacuum) is achieved with a uniform evacuation, test specimen with a hose length which has a free length of 1 m = 3 ft between the hose spigots / fittings.
  • Conditioning: The test may be carried out at the earliest 24 hours after the hose length has been produced. The test specimens must be conditioned at least three hours before the start of testing at room temperature.
  • Procedure: The test specimen is installed in a test device, by pushing the hose onto the test pieces and fixing it with hose clips without damaging the hose. The test specimen must be stretched and aligned as straight as possible in the test fixture. The outer diameter of the test sockets corresponds to the internal diameter of the sample body and is designed in such a way that the test medium cannot escape during the test. A test fitting is rigidly connected to the test device and is non-rotatable. The other test piece is rotatable and then mounted. Next, a twisting of the test piece during the test is thus possible. The carriage is mounted moveable in a axial direction, which means that it is possible to change the length of the sample during the test. Vacuum strength is the one minute pressure that remains unchanged, with a 10 % shortening of the hose. The corresponding vacuum strength values shall be indicated. The test requirement of a maximum of 10 % shortening can lead to no values being determined for hoses with wall thickness up to 0,6 mm = 0.025 inch.
  • Test results: As a test result, the vacuum is measured at a hose shortening of 10 %. Additionally we show sometimes in brackets vacuum figures for 1 m = 3 ft long straight and axially fixed hose lengths close to collapsing as some other manufacturers but we do not advise to operate the product under these conditions. Due to the design, the 10 % hose shortening of some PROTAPE® hoses with wall thicknesses of 0,4 to 0,6 mm = 0.015 to 0.025 inch cannot be measured and in these cases we name recommended operating limits.

Do you have questions about pressure ratings and the associated measurements? The NORRES competence team will be happy to help you!

 

Engineering modifications subject to change.