Luer and small-bore connector torque testing

Requirement

International standards relevant to small-bore connectors for liquids and gasses in healthcare applications focus on their ease of use and resistance to leakage or mishandling. The current ISO 80369 standards cover a set of test methods, which provide a broad matrix of functionality checks recommended for quality assurance in such components. Mecmesin torque and force testing systems assist you with preparing connectors for performance testing according to these ISO methods.

Small-bore connectors are used in medical devices or accessories intended for use with a patient and convey liquids or gases in healthcare applications ranging from anaesthesiology, neuro-radiology, oncology, haematology and radiology, through to in vitro diagnostics laboratory and pharmacy activities.

The current standard, ISO 80369-20 specifies the test methods to evaluate the performance requirements for small-bore connectors. Other methods described in withdrawn and superseded standards (e.g. ISO 594 and BS EN 1701) are broadly identical and are still followed by some medical device manufacturers, as the FDA continues to recognise devices tested to this method until 31.12.2019.

The latest ISO 80369 documents have been revised as different connector designs have been restricted to certain fields— the well-known 6% taper Luer varieties now being limited to intravascular or hypodermic syringe applications. Also included is additional clarification for locking, non-locking (slip) and floating or rotating-collar connectors. The ease-of-assembly test, present in ISO 594, was considered too subjective and removed. However the equipment used here is suitable for evaluating this functionality by correlating to user perception.

ISO 803969 test standards are designed to ensure ease of use for those using these components; patients themselves, relatives, home-care providers as well as clinical users such as physicians, nurses and emergency medical technicians.

Part 20 of ISO 80369 covers test methods to evaluate the connector system’s performance against:

• leakage,
• stress cracking,
• resistance to overriding,
• disconnection by unscrewing, and
• resistance to separation by axial force.

These methods are used to indicate the performance values appropriate to connectors described in:

• Part 7: IV and hypodermic (6% Luer) connectors.
• Part 3: Connectors for enteral applications.
• Part 5: Connectors for limb cuff inflation applications.
• Part 6: Connectors for neuraxial applications.

Solution

The force and torque apparatus for these methods require an appropriate male/female ‘reference connector’ (or ‘reference fitting’) in order to test the mating specimen connector. A dimensionally different reference connector may be required for different tests. All methods require preparation of the test joint connection to be to a consistent specification; by the application of a simultaneous axial force and a light torque of the order of 0.08 – 0.12 N.m.

Mecmesin’s Helixa software-controlled precision torque measurement system, with its ability to apply an axial load, is ideal for this procedure.

The means of evaluation of the assembled specimen against the performance requirement varies; with visual inspection or measurement of pressure being relevant to several tests.

The tests of “resistance to separation by axial load”, “disconnection by unscrewing” and “resistance to overriding” all require force or torque testing systems to apply the load and measure the resulting parameters against acceptable values. Pass or fail criteria are easily checked and indicated with software-controlled Mecmesin systems. Additionally, the captured data enables Luer connector manufacturers to implement ISO 80369 Annex J and generate variable data for statistical analysis. As a manufacturer you not only receive a single load value but also benefit from a graphical output, which provides much more insight into the performance characteristics of the test specimen. Mecmesin’s fully programmable software easily enables R&D departments to apply unique loading conditions beyond the requirements of the test standard.

The precision afforded by the torque tester integrates perfectly with the robust VectorPro software, which has functionality and back-end architecture to support organisations in the medical devices industry. Meeting 21 CFR Part 11 compliance for electronic records and signatures is fundamental in this domain.

Audit trail of actions, with events logging against authorised users is recorded with security of records provided by the option of SQL database implementation.

Test equipment

• VortexPro, HelixaPro (previously Vortex or Helixa) torque testing system
• ETC (previously HTC or ITC Torque Sensor) of 0.3 N.m maximum
• OmniTest (or MultiTest) tensile testing system with an appropriate loadcell for axial pull-off measurement (50 N)
• VectorPro software (previously Emperorᵀᴹ Torque and Emperorᵀᴹ Force fully programmable software)
• Appropriate Luer reference connectors