The Principle and Method of Waterproof and Flow Test of Filter Membrane of Infusion Set

In medical infusion sets, the filter membrane is a key component to prevent particles, air bubbles and bacteria from entering the patient's blood. Membrane materials are usually hydrophobic (water-repelling) to prevent water or any liquid from penetrating the membrane surface. The test method generally used in the laboratory is to test the water resistance of the filter membrane to ensure that the membrane can effectively prevent the passage of water while still allowing air to pass through, because this is essential to maintain a sterile barrier in the infusion system.

The main reason why water cannot seep from the membrane surface is the hydrophobicity of the membrane material, which forms a barrier that water cannot penetrate, but air can still pass through. The waterproof test usually adopts the WBT (water breakthrough test) method. Take 30-50PCS of film samples, set the pressure<=0.19kgf/cm2, 0.10kgf/cm2, and the time setting range is 5 seconds, and carry out the waterproof test. The final result is that no water can seep out of the surface of each PCS, otherwise it will be judged as a substandard product.

Flow testing of filtration membranes is usually done by applying a specific pressure to one side of the membrane and then measuring the flow of air or gas through the membrane under these conditions. The goal is to ensure that the membrane allows adequate air flow rates while preventing fluid and particles from passing through. The exact flow rate a membrane should achieve may vary depending on the requirements of the specific application and the standards set by regulatory agencies. However, the general standard for infusion set vents is that they should allow an airflow rate of at least 1 L/min at a pressure of 300 mbar while not allowing water to pass at a pressure of up to 200 mbar.
For example, ISO 8536-4:2010 is a standard that specifies design and performance requirements for infusion sets (including filter membranes), and ISO 8536-5 specifies requirements for disposable infusion sets (including filter membranes) with a maximum capacity of 1,000 mL and a maximum infusion rate of 1,000 mL/h. The infusion time required for each 100ml is less than 330 seconds, aiming to ensure the safety and effectiveness of the infusion process. The infusion time here refers to the time required to infuse a given volume of fluid (in this case 100 mL) through the infusion set. An infusion time that is too fast may result in an overdose, while an infusion time that is too slow may result in underdosing or ineffective treatment.

The test method for the filtration membrane flow rate in the laboratory is also in compliance with the ISO 8536-5 standard. By setting the maximum infusion time to 330 seconds per 100 ml, take 20-30 PCS of membrane samples, and use 100ML as the test volume to conduct a speed test. If it is lower than 330 seconds, it should not be too slow in principle. Usually, the membranes that meet the specifications are all above 100 seconds. Of course, the main purpose here is to control the upper limit. For the lower limit in actual use, press the Adjust to the actual situation.

The use of medical filter membranes is related to the safety of human life. Therefore, the safety standards stipulated by the country must be followed from production, testing to use. The specific details may vary depending on the country and region, depending on the exact nature of the infusion set and detailed regulations. Therefore, all industries involved must refer to relevant local regulations and guidelines to obtain the most accurate information.