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Analysis of leak detection methods for HEPA filter Aug 10, 2018

In the purification system, the HEPA filter is the key equipment.leakage detection for HEPA filter is the key equipment. leakage detection for HEPA filter. The purpose is to determine whether filter itself and the system installation has significant leakage take for remedial action.

HEPA filters are installed or replaced after a certain period must detect again.

DOP method is widely used in the world. Leak detection instruments used are: DOP generator, aerosol photometer.The dust sourch of DOP method is DOP solvent, spray out become to particles, since the leakage detection principle of DOP is to generate DOP aerosol on the windward side of the filter as test dust source, and sample with a photometer on the down wind side. The dust through photometer generate scattered light, by photoelectric effect transformed and amplified into electric, and display quickly by microammeter. The relative concentration of aerosol can be measured by a photometer.Check a filter in 5 minutes.Its characteristic is  fast and simple, accurate and reliable. However, according to international data, DOP solvent dust dource, has been pointed out to have mutagenic properties.

But because DOP leak detector very expensive difficult to equip with.For this reason, the expert of clean technology of air conditioner and drug production workshop designer discussed how to solve the problem of leakage detection of purification system for general enterprices. Studied the drug production verification guide of the principle of air clean technology, It is believed that the traditional dust particle counter method can slso achieve the purpose of detecting the leakage of HEPA filter. The method is introduced as flolows.

1, Test method: Dust particle count scanning method

2, Test range: between the filter material of the filter, the seal of the filter frame and the support frame of the filter group

3,Detection instrument: dust particle counter

4,Testing principle: According to the particles in a certain intensity of light will cattering luninous flux is proportional to its particle size this principle.After amplification and computer processing, the particle equivalent diameter and corresponding particle number are displayed.

5, Detection procedure:

5.1 Dust particle counter is used to scan the air outlet side of the filter, and the samplling head is about 2cm distance from the filter. The scanning speed is less than 5cm/s.

5.2 When the cetection period is 10min., the number of 0.5 um paticles isTwo methods, DOP leak detector and dust particle counter, are qualified test methods for air conditioning purification system.>20and the alarm sounds, indicating the start of the leakage, need mending or more.

5.3 After plugging the leakage or fastening the bolt with epoxy resin, carry out th scanning inspection.

6, Detection period 

6.1 Normal use shall be tested at least once every quater

7.2 Newly installed high efficiency filters shall be tested.

Although the detection time is longer by using the dust counter scanning method, generally it takes one hour for filter to detectg leakage, but testing equipment is cheap, there is no negative effect hidden danger, it is more suitbable for general drug manufactures, Two methods, DOP leak detector and dust particle counter, are qualified test methods for air conditioning purification system.