Field case of air filter in cleanroom-Filter enjoying "Turkish bath"

The air conditioning box in the clean workshop of Factory C is manufactured by a new air conditioning factory. It is said that the designer of the air conditioning box is an air conditioning expert from Southeast Asia. The factory began to operate in early autumn. Soon, the weather became cool and the air was dry. The indoor air humidity required by the process was 57 ± 5%. Therefore, the air conditioner enters the humidification operation state, and the humidification of the air conditioning box directly uses steam. On the second day of humidification, the problem occurred: the temperature in the plant rose, the humidity fell, and all products on the production line were scrapped. We immediately organized experts to check the fault, and found that the air supply volume of the air conditioner was small, there was more water in the air conditioner box, and all the medium efficiency filters near the humidifier were wet. The control system of the air conditioner still commands the humidification of the air conditioning system because it detects that the indoor humidity is low. The spray pipe of the humidifier spurts dry steam (the drainage works normally), forms wet steam when encountering cold air, and soaks the medium efficiency filter only 50cm away from the humidifier. After the filter is soaked in water, the wind resistance increases sharply, resulting in the reduction of the air volume of the air conditioner. If more steam is added, it will not reach the clean workshop and will be left in the air conditioning box.

Some filter manufacturers took the opportunity to come to Factory C to promote the "anti wetting filter". We tested several times, and none of the filters could withstand that kind of steam bath for a long time. Several manufacturers failed several tests, and nothing happened.

Southeast Asia has a tropical marine climate, and almost all air conditioners operate in dehumidification state. We estimate that the expert seldom encountered humidification problems in the past. Our working environment needs to be humidified for half of the year. The humidification control of that air conditioner has only one switch, and the humidification amount is not adjustable. When humidification is required, the valve will be fully opened once, and the ejected steam will immediately condense into liquid water when it meets the cold filter surface. In addition, the outlet of the steam nozzle is too close to the filter and the atomization distance is too short, so the steam containing small water droplets is blocked by the filter as particles before it is fully diffused into gaseous water. If the filter is blocked by water, the air conditioning system will be disordered.

After finding the reason, we replaced the simple switch control with a linear steam regulating valve with good linearity, which widened the distance between the humidifier and the filter, and added a spoiler. After taking these measures, the phenomenon of moisture wetting the medium efficiency filter will no longer occur.