YY/T 0681.4-2021Test methods for sterile medical device package - Part 4: Detecting seal leaks in porous packages by dye penetration (English PDF)

2.1 Wicking

The liquid moves into the fibrous material.

2.2 Dye penetrant

A mixed aqueous solution of a coloring agent and a surfactant, which is designed to indicate the location of the defect in the period before wicking (which masks the existence of the defect).

2.3 Channel

Any undamaged path across the entire width of the intended sealing area.

If conditioning is required, it is recommended to be performed in a standard environment where the temperature is (23±2) °C and the relative humidity is (50±2) %; the conditioning shall last for at least 24 h before the test.

9.1 Method A (injection method)

9.1.1 Inject a sufficient amount of dye penetrant into the package, so that the dye penetrant can form a depth of about 5 mm on the longest side of the package. When piercing the packaging bag and injecting the dye penetrant, special care must be taken not to pierce or damage other surfaces of the package. It is easier to pierce in the position beside the virtual sample in the package. The sample will act as a bulge to separate the two surfaces of the packaging bag, so as to reduce the risk of accidentally piercing the two surfaces.

9.1.2 Visually inspect the sealing area through the transparent surface of the package. Observe the sealing area through which the dye penetrant flows, and the channel can be directly observed. For packages that are sealed on four sides, it's at most 5 s for each side, and the total time is less than or equal to 20 s. The long stay of the dye penetrant will cause the sealing area to be dyed due to the wicking of the porous material, making observation difficult. If necessary, use a 5 ~ 20 times optical magnifying glass for detailed inspection.

9.1.3 The packaging bag must be rotated, so that each side is in contact with the dye penetrant. If necessary, add more dye penetrant to ensure that each side can be in contact with the dye penetrant.

9.2 Method B (edge immersion method)

9.2.1 Choose a container of sufficient length to at least contain the longest sealed side of the to-be-tested package.

9.2.2 Pour enough dye penetrant into the container, so that the dye penetrant can cover the bottom of the container, with a minimum depth of about 3 mm ~ 6 mm. If there is extra material on the outer edge of the seal of the tested packaging bag, such as the skirt for the opening, some modifications must be made to the packaging. Use a cutting tool to cut off the excess material from the skirt along the outer edge of the sealing area at a distance of 3 mm; be careful not to cut it into the sealing area. Cutting off the excess material will bring the dye penetrant close to the sealing area.

9.2.3 Immerse one of the sealed edges of the package down into the dye penetrant so that the entire sealing edge of the sealing area is in contact with the dye penetrant for a short time. This immersion operation is short, but it is just enough to completely wet the sealing edge.

9.2.4 Remove the package along the immersion direction; confirm that the entire sealing edge is in contact with the dye penetrant. Observe the penetration of the dye penetrant in the sealing width direction of the package from the transparent surface of the package. For packages that are sealed on four sides, it's at most 5 s for each side, and the total time is less than or equal to 20 s.

9.2.5 If necessary, use a 5 ~ 20 times optical magnifying glass for detailed inspection.

9.2.6 Repeat the above edge immersion operation for other sealing sides.

9.3 Method C (drip method)

9.3.1 Pour the dye penetrant into an open container.

9.3.2 Use fingers or a paper clip to carefully separate the skirt of the transparent material from the porous material.

9.3.3 Insert the eye dropper or pipette into the dye penetrant.

9.3.4 Face the transparent surface of the package to the operator; drip the dye penetrant along the sealing side between the transparent material and the porous material. Make sure that the entire side is immersed in the dye penetrant.

9.3.5 For small packaging bags, slowly rotate the packaging, while continuously dripping the dye penetrant, until the sealing side of the whole package is in contact with the dye penetrant. If it is inconvenient to operate, drip on only one side at a time.

9.3.6 Observe the penetration of dye penetrant along the entire width in the sealing area of the package. For packages that are sealed on four sides, it's at most 5 s for each side, and the total time is less than or equal to 20 s.

A.2 Edge immersion method and drip method

A.2.1 Test example

Laboratory studies on the edge immersion method and drip method in the standard were carried out in 2012. 12 laboratories participated, 7 of which tested the edge immersion method, and 5 tested the drip method. The defect is made by the wire of 50 µm that is artificially placed in a sealing area; after the wire is drawn out, a channel of the same diameter as the wire is formed. For 5 materials, each laboratory tested 50 samples (25 with channels and 25 without channels). Each laboratory reported the presence or absence of the channel.

Put all the results into the table, and there are results of correct recognition, false positive and false negative.

A.2.2 Edge immersion method test results

A.2.2.1 When the edge immersion data of all laboratories are combined, the results show that these two methods also have a 95% accuracy rate for 50 µm channels. The 95% confidence interval ranges from 93.8% to 96%. Table A.2 ~ Table A.4 show the results of correct recognition, false positive and false negative.

A.2.2.2 When using the analysis of variance to compare the edge immersion laboratories, the test results of the laboratories 6520 and 6521 are significantly different from those of the other 5 laboratories. This may contain other reasons causing a larger error rate. If the results of these two laboratories are not recorded, the accuracy can be increased to 98%.

A.2.2.3 The remarks of laboratory

6521 describe the observation that some samples have a unique path highlighted by the dye penetrant, but only part of them pass through the sealing area of the package. These samples cannot be recorded as having channel defects. Because the definition of the channel is a complete channel through which the dye penetrant can pass through the entire sealing area. All partial channels in this laboratory are considered channels

B.1 Wicking

The dye penetrant used in this Standard has strong activity and will quickly pass-through TYVEK or other porous materials to produce wicking. It will partially penetrate the sealing area and cause a false judgment as a test failure.

The difference is that the channel defect in the sealing area provides a path through the entire sealing area, which will be found immediately when exposed to the dye penetrant. The test time is very important because it can distinguish between wicking and channel leakage. The test time is 5 s, because the penetration in the channel will be clearly noticed in the first few seconds. If the penetration time of the dye penetrant is 20 s, the wicking will be more serious.

For the entire package, 20 s is the maximum exposure time, that is, 5 s x 4 = 20 s.

B.2 Oxidation sterilization

The oxidation sterilization process can change the hydrostatic pressure of the porous material. Due to excessive wicking, this change in surface tension can cause false positive results. Before conducting a liquid-based seal integrity test, it is very important to evaluate the effect of sterilization on the hydrostatic pressure of the material.

B.3 Bending/folding

When the permeable and porous material is bent, folded or wrinkled, it may cause false positive test results. Folding will cause the internal sealing area to separate from the venting surface. This happens when the bag needs to be folded to match a container or the bag needs to be folded or bent during a pressure test. Folding porous materials is not recommended, but in most cases, it is difficult to avoid. Sheet separation can be observed in all porous panel materials. The porous material is easy to be separated, because the outer surface of the porous material is less flexible than the inner surface. The bending will make the inner fiber material and the board tightly to be bond together. The tighter the bend, the greater the force value. Until the load is overloaded, the fiber structure fixed together with materials will separate and compress on one side of the bend, and expand on the other side, forming a gap or channel between the fibers inside the bend. When the material becomes straight or flat again, there will still be low-strength areas or gaps inside the material. For porous materials, such a channel will be formed between the soft