Various air filter use site cases

Various air filter use site cases

Summary

Analyze several typical cases of the use of electronic factory filters, and introduce ideas and methods to solve those problems. Issues include design, filter performance and quality, and field operations. Experience has shown that as long as the work is done carefully, many faults can be avoided or eliminated in time.

Air filters are used extensively in electronics factories. The author is an ordinary engineer who is on the scene all the year in the power plant of the electronics factory. In the process of dealing with the filter, my colleagues and I have encountered many faults, and those faults and troubleshooting procedures are headaches, but they are very instructive. The following paragraphs may give some inspiration to the peers.

Case 1, the pre-filter can not be broken

A clean room clean room producing color display, the construction time is not long, the air supply air supply volume is reduced, the temperature and humidity are out of control, the temperature is far higher than the set value of 22±1°C, reaching 30°C, and rising with the outside temperature. High and rising. The positive pressure of the factory building and the outside world is also out of control, and the dirty air from the outside enters the plant along the conveyor path of the material. The indoor cleanliness exceeds the standard and it is necessary to stop production.

The maintenance personnel immediately find the fault. First, it is suspected that the filter is clogged. First remove the filter at the end of the clean house and remove it to see that the HE is not dirty. Next, remove the medium-efficiency filter in the air-conditioner. It is a bit dirty. It is cheaper than HE. First, the first-effect filter in the air conditioner is the cheapest and new. After some tossing, I did not see how much air supply increased, but turned to the problem of the filter itself. The manufacturer came to do a comparative test, and the same batch of filters was given to the problem factory and another factory. Replace it for use. As a result, the problematic factory problem remains, while the other plant is functioning properly. The test showed that it was not a problem with the company's filter.

Next, we carefully inquired along the air-conditioning system, and the careful people found that the newly-removed primary filter had a crack in the filter cloth near the frame. After further investigation, the reason was found: the filter cloth was made of fiberglass, and the operator accidentally broke it. The broken filter material is blown onto the heat exchanger together with the dust. In the early summer, the chilled water was passed through the heat exchanger, and the condensed water on the surface of the heat exchanger made the dust and broken fibers become mud, and the heat exchanger was dead. The airflow passage is blocked, and the cold wind does not enter the factory, and the temperature and humidity are out of control.

We spent several tens of thousands of dollars, hiring people to clean the heat exchanger year after year, the problem was solved, and since then, the operator remembered to take care when replacing the filter. We also got another inspiration from it, and encountered a filter that used a long time to resist the alarm, maybe it was broken, and the airflow was short-circuited.

Case 2, the seal of the filter

The HE filter has a ring of elastic seals on the frame that fits snugly against the sealing end faces of the high-efficiency air supply. During the use process, some maintenance and construction personnel will stand on the tuyere. If the care is not careful, or the structure of the high-efficiency air supply port is inferior, the structure of the tuyere may be deformed, and there is a gap between the filter and the sealed end of the structure. The air enters the purification plant from the gap and destroys the cleanliness. This phenomenon can not be detected in a short time, we thought it was a problem with the HE filter, but for a long time, there will be dust marks around the gap. When it is found that the cleanliness is beyond the standard, we first open the flow orifice plate of the air supply port and use the instrument to check for air leakage. In addition, the seals on some HE filters are elastic, semi-circular cross-section, continuous jointless seals, which are in line contact with the filter mounting end faces, while other HE seals are four flat mats. It is face contact. Line contact seals are preferred over face contacts.

The primary and secondary filter in the air-conditioning box generally does not have a gasket, and it is difficult to detect even if it leaks around the air during operation. If there is a lot of air leakage, the differential pressure resistance reading may not increase normally, but the HE filter at the end of the clean room protected by these pre-filters is not effectively protected, and the service life will be shortened.

Sometimes the pre-filter is not efficient, but the life of the protected HE filter is still short. That problem is often found in the pre-filter seal in the air conditioning box. Although not as strict as the HE filter seal, it must be sealed. The air conditioning box should provide a reliable sealing structure for the filter. There are good performance seals, but also a convenient and reliable clamping mechanism. If the clamping mechanism is missing or those mechanisms are not working properly, the air will return when the air conditioner is turned off, and the filter may be blown off. The filter is not in the home position, which is equal to the absence of the filter section. At the site, pre-filter sealing and clamping faults often occur, with equipment problems, filter problems, and operational problems.

Case 3, filter enjoy "Turkish bath"

The air conditioning box of the clean factory of Factory C is manufactured by a newly-built air-conditioning factory. It is said that the designer of the air-conditioning box is an air-conditioning expert in Southeast Asia. The factory started running in the early autumn. Not long after, the weather turned cold and the air was dry. The indoor air humidity required by the process was 57±5%, so the air conditioner entered the humidification operation state, and the humidification of the air conditioner box directly used steam. On the second day of humidification, the problem arose: the temperature inside the plant rose, the humidity dropped, and all the products on the production line were scrapped.

We immediately organized an expert to check the fault and found that the air supply volume of the air conditioner was small, and there was more water in the air conditioner box. The medium efficiency filter close to the humidifier was all wet, and the air conditioner control system was still detected due to low humidity in the room. The air conditioning system is commanded to humidify. The nozzle of the humidifier sprays dry steam (hydrophobic normal work). When it encounters cold air to form wet steam, the medium efficiency filter is only 50cm away from the humidifier. After the filter soaks in water, the wind resistance increases sharply, causing the air conditioning to reduce the air volume. Adding more steam, it is not possible to get to the clean plant, and it stays in the air conditioner. Some filter manufacturers took the opportunity to come to the C factory to promote the "anti-wet filter". We tested it several times. No filter can withstand the steam bath for a long time. Several manufacturers have tried several times without success, and they have not moved.

Southeast Asia is a tropical maritime climate, and air-conditioning boxes are almost always dehumidified. We estimate that the experts rarely encountered humidification problems in the past. In our working environment, we need to humidify half of the year. The humidification control of the air conditioner has only one switch, and the humidification amount is not adjustable. When humidification is required, the valve is fully opened, and the sprayed steam encounters the surface of the cold filter and immediately condenses into liquid water. In addition, the steam nozzle outlet is too close to the filter, the atomization distance is too short, and the steam containing small water droplets is blocked by the filter as particles before it is completely diffused into gaseous water. The filter was blocked by water and the air conditioning system was messed up.

The reason was found. We changed the simple switch control to a linear steam regulator with better linearity, widened the distance between the humidifier and the filter, and installed a spoiler. After taking these measures, there is no longer a phenomenon in which the water vapor wets the medium effect filter.

Case 4, filter life

The service life of the HE filter is related to the amount of air in the air conditioner. Our company has been building factories for more than 10 years. The service life of high efficiency filters in early plants is generally 5 years. At the beginning of 2001, a new workshop was put into operation. After more than two years, the resistance of the high-efficiency filter reached 650 or more, and the filter was scrapped. When we found the reason, we found that the workshop's 1220×610mm, high-efficiency filter design air volume is 3150m3/h, which is much higher than other workshops in our company.

The life of the filter is also related to the quality of the air supply in the air conditioner. It is also the C factory mentioned in the previous case. There is a large factory building of 400 meters long and 50 meters wide in the north of the factory. The weather in autumn, winter and early spring is relatively dry, and it often blows north wind. The dust that rises with the wind directly hits the C plant. The primary filter on the air conditioning box in the C building was blocked in less than half a month. In the D building, which is far away from the C plant, the replacement period of the filter in the air conditioning box is normal. At that time, it was thought that the filter used in the C plant had a low dust holding capacity. We observed the filter material with a microscope and saw that the size of the dust particles accumulated on the filters of the C and D buildings was different. The diameter of the particles on the filter replaced by the C factory was significantly larger. The air conditioner in the C plant draws in a lot of dust, and the service life of the filter is of course short.

The forklift is required in the E factory, and the diesel engine is used in the initial stage because the diesel forklift is powerful. But these diesel forklifts also make the filter problem. The incompletely burned multi-carbon oxides disperse in the air, enter the air-conditioning box through the return air, and condense on the filter. We observed with a high power microscope and found that the agglomerates were semi-flowing on the primary and secondary filters. Those condensates may migrate to the back of the filter and volatilize due to uneven heating and humidified air, entering the downstream HE filter, exacerbating the clogging of the HE filter. Later, the E factory switched to an electric forklift, which reduced the chemical pollution in the plant and eased the filter blockage.

In a highly automated production line, no one can observe such a small particle splash with the naked eye, and everyone is accustomed to blaming the purification system. Filter promoters don't have the habit of wearing overalls, they rarely go to the site to help us find the cause, and often these customers are clarifying their responsibilities.

In the process of daily processing of the filter, I got the patient and meticulous help of my colleagues, and I was encouraged and supported by the leaders. Dr. Cai Jie from the Chinese Academy of Agricultural Sciences has suggested that I summarize the filter failures I have encountered and urge me to write this article.

Note: The above information comes from the Internet!

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