Five common leak detection methods of high efficiency filter!
Five common leak detection methods of high efficiency filter!
As one of the testing items in the clean workshop, the leak detection of high efficiency filter has been paid more and more attention by us since the implementation of the 2010 GMP. Now, it has become a must check item for pharmaceutical enterprises. More and more units in hospitals, electronics, food, cosmetics and other industries carry out leak detection of high-efficiency filters. The following is a detailed introduction to the leak detection method of high efficiency filter
1、 Sodium flame method
The test dust source of sodium flame method is sodium chloride salt spray of multi loose phase, and the "amount" is the brightness of hydrogen flame when burning with salt spray.
The brine splashes under the agitation of compressed air, forms tiny salt crystal particles through drying and enters the air duct, and samples before and after the filter.
The salt fog sample makes the color of the hydrogen flame blue and the brightness increase. The brightness of the flame is used to determine the salt fog concentration of the air, and to confirm the filter power of the filter for salt fog.
The primary detection instrument is the flame photometer. This method can only detect sponge with low sensitivity, and cannot detect ultra-high efficiency filter.
2、 Oil mist method
The test dust source of the oil mist method is oil mist, and the "amount" is the turbidity of the oil mist air. The filter power of the filter to oil mist particles is determined by the difference in the turbidity of the gas samples before and after the filter.
In Germany, paraffin oil is specified to be used, and the particle size of oil mist is 0.3~0.5 μ m. When the oil mist method is used to detect the filter, it simply causes damage to the filter, and cannot directly read the value, which wastes time.
3、 DOP method
This method was once commonly used internationally to test the sponge of high efficiency filter.
Its test dust source is 0.3 μ m single loose dioctyl phthalate (DOP) droplet, also known as "hot DOP", and "amount" refers to the turbidity of air containing DOP.
The DOP liquid is heated into steam, and the steam condenses into tiny droplets under specific conditions. After removing the oversized and undersized droplets, particles of about 0.3 μ m are left, which enter the air duct. After measuring the turbidity of the gas sample before and after the filter, the filter power to 0.3 μ m dust is determined.
4、 Fluorimetry
The test dust source of fluorescence method is sodium fluorescein dust generated by spray.
The test method is to first sample before and after the filter sponge, then dissolve the sodium fluorescein on the sampling filter paper with water, measure the fluorescence brightness of the aqueous solution containing sodium fluorescein under specific conditions, and the brightness reflects the weight of the dust, so as to calculate the filter power of the filter.
5、 Particle counting
This method is commonly used in Europe, and the test method of ultra high efficiency air filter in the United States is also similar, which is the current international mainstream sponge test method.
The dust source is multi loose phase liquid drop or solid dust with confirmed particle size. Sometimes, the filter manufacturer shall use atmospheric dust or other specific dust according to the special requirements of users.
If the condensation nucleus counter is used in the test, it is necessary to use a single loose phase experimental dust source with known particle size. The primary measuring instrument is the high flow laser particle counter or condensation nucleus counter.
The counter is used to scan and check the whole air outlet surface of the filter. The counter gives the number of dust at each point and can also compare the local power of each point.
