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ISO 594 | Medical Devices and Equipment | Axial-Torsion Testing

ISO 594 is a testing standard that defines and measures the general requirements for 6% taper conical fittings. The requirements tested in this method include gauging, liquid and air leakage, separation force, unscrewing torque, ease of assembly, resistance to overriding, and stress cracking. A noteworthy additional standard, ISO 80369, focusing on small bore tubing connections has been and currently is in a global collaborative development. This standard aims to reduce cross connections between applications through connector differentiation.

An axial-torsion testing system is required to test Luer fittings. ADMET’s eXpert 8602 Axial-Torsion test system is designed to be a completely automated Luer Fitting assembly and testing solution. This equipment allows the end user to assemble the fittings within the loads set forth in the new ISO 80369 and the older ISO 594 standards. Tests should be carried out using the appropriate reference fitting, the dimensions and material of which are in accordance with those explained in the standard.

Before conducting ISO 594, it is important to read the entire specification in the relevant ISO publication.

ISO 594 | Medical Devices and Equipment | Axial-Torsion Testing

  1. Test Procedure to Test Liquid Leakage: Connect the sample fitting to the reference fitting by applying an axial force not exceeding 27.5N (6.18 lbf) while applying a torque not exceeding 0.12 Nm (1.06 inlbf). Introduce water into the fitting assembly making sure the outside of both fittings is dry. With the axis of the lock fitting horizontal, seal the assembly outlet and bring the internal water pressure up to 300 kPa to 330 kPa. Maintain the pressure for 30 seconds. Check for liquid leakage. Record the results.
    1. Test Procedure to Test Air Leakage of a Male Fitting: Connect the sample male fitting to the female reference fitting by applying an axial force not exceeding 27.5N (6.18 lbf) while applying a torque not exceeding 0.12 Nm (1.06 inlbf). Connect the female reference fitting, via a leakproof joint of minimal volume, to a syringe. Draw into the syringe, through the assembly, a volume of recently boiled and cooled water. Adjust the volume of the water to 25% of the graduated capacity of the syringe. Occlude the device below the fitting assembly. With the nozzle of the syringe pointing downwards, withdraw the plunger to nominal capacity. Hold for 15 seconds and check for air leakage. Record the results.
    2. Test Procedure to Test Air Leakage of a Female Fitting: Connect the sample female fitting to the male reference fitting by applying an axial force not exceeding 27.5N (6.18 lbf) while applying a torque not exceeding 0.12 Nm (1.06 inlbf). Connect the male reference fitting, via a leakproof joint of minimal volume, to a syringe. Draw into the syringe, through the assembly, a volume of recently boiled and cooled water. Adjust the volume of the water to 25% of the graduated capacity of the syringe. Occlude the device below the fitting assembly. With the nozzle of the syringe pointing downwards, withdraw the plunger to nominal capacity. Hold for 15 seconds and check for air leakage. Record the results.
  2. Test Procedure to Test the Separation Force of the Fitting Assembly: Connect the sample fitting to the reference fitting by applying an axial force not exceeding 27.5N (6.18 lbf) while applying a torque not exceeding 0.12 Nm (1.06 inlbf). Apply an axial force progressively up to 35 N (7.86 lbf) at a rate of 10 N/s and maintain it for at least 10 seconds. Record the force at separation.
  3. Test Procedure to Test the Unscrewing Torque of Fitting Assembly: Connect the sample fitting to the reference fitting by applying an axial force not exceeding 27.5N (6.18 lbf) while applying a torque not exceeding 0.12 Nm (1.06 inlbf). Apply an unscrewing torque of 0.02 Nm and maintain it for at least 10 seconds. Record the results.
  4. Test Procedure to Test the Ease of Assembly: Mount the sample fitting to the reference fitting by hand. For semi-rigid fittings, apply an axial force not exceeding 20N (4.5 lbf) together with a torque not exceeding 0.08 Nm (0.7 inlbf).
  5. Test Procedure to Test the Resistance to Overriding: Connect the sample fitting to the reference fitting by applying an axial force not exceeding 27.5N (6.18 bf) while applying a torque not exceeding 0.12 Nm (1.06 inlbf). Apply a torque not less than 0.15 Nm (1.33 inlbf) to the fitting and hold constant for 5 seconds. Record the resistance force.
  6. Test Procedure to Test Stress Cracking: Connect the sample fitting to the reference fitting by applying an axial fore not exceeding 27.5N (6.18 bf) while applying a torque not exceeding 0.12 Nm (1.06 inlbf). Allow the fittings to remain assembled for 48 ± 1 h at 20 ± 5 ˚C (68 ± 41 F).

ISO 594 | Medical Devices and Equipment | Axial-Torsion Testing

ISO 594 Recommended Equipment
Testing System
Fixturing
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