Field case of air filter in cleanroom-Consequences of pre-filter damage

A clean workshop producing color displays has not been built for long. The air supply volume of the air conditioner has become smaller, and the temperature and humidity are out of control. The temperature is far higher than the set value of 22 ± 1 ℃, reaching 30 ℃, and increases with the increase of the external temperature. The positive pressure between the building and the outside is also out of control, and the dirty air from the outside enters the building along the conveyor belt. The cleanliness of the room exceeds the standard, and production will be stopped.

The maintenance personnel immediately find ways to find and solve the fault. First, they suspected that the filter was blocked. They removed the HEPA filter at the end of the clean plant and found that HEPA filter was not dirty. Then, they remove the medium efficiency filter in the air conditioning box, it is a bit dirty. It is cheaper than HEPA filter, so replace it first. The primary filter in the air conditioner is the cheapest, and it is also replaced with a new one. After these replacements, we didn't see the air supply volume increased.

Instead, we suspect that the problem is the filter itself. The manufacturer sent someone to do a comparative test, and provided the same batch of filters to the factory that gave the problem and another factory, and replaced them with new ones. As a result, the problem of the faulty factory remained, while the other factory was operating normally. The test shows that it is not the filter problem.

Next, we checked carefully along the air conditioning system. Careful people found that there was a crack in the filter media near the frame of the primary filter. After further investigation, the reason was found: the filter media was made of glass fiber, and the operator accidentally broke it. Broken filter debris is blown to the heat exchanger together with dust. In early summer, the heat exchanger was filled with chilled water, and the condensed water on the surface of the heat exchanger turned dust and broken fibers into mud, which made the heat exchanger dead. The airflow channel is blocked, and the cold air cannot enter the plant, so the temperature and humidity will lose control.

We spent tens of thousands of RMB to hire people to clean the heat exchanger year by year, and the problem was solved. Since then, the operator has remembered to handle the filter with care when replacing it. We also got another inspiration from it. The filter that has used resistance for a long time but still does not alarm may be broken and the air flow is short circuited.