What is the difference between ULPA filter and ordinary air filter?

Let me first talk about a fact that is easily overlooked: these two types of products have different problems to solve when designing.

The task of ordinary air filters (primary efficiency, medium efficiency, etc.) is to protect the equipment behind, reduce the end load, and maintain the air quality of the general ventilation environment. ULPA's mission is to control fine particles at the end of the process. Different goals lead to different evaluation methods, testing requirements and installation conditions.

Putting them together to compare 'whose filtering accuracy is higher' is equivalent to asking 'which one is better, a wrench or a screwdriver' - there is no problem with the tools, the problem is that they are used to do the same thing.

The evaluation systems are different and the values ​​cannot be directly compared.

Ordinary ventilation filters are usually evaluated according to the standards of general ventilation filters. The efficiency indicators may be gravimetric efficiency, colorimetric efficiency or filtration efficiency corresponding to a certain particle size. ULPA evaluates according to the relevant system of high-efficiency filters, focusing on the penetration rate under the specified particle size and the judgment of the overall and local levels.

The testing methods, particle size selection and measurement calibers of the two are different. It is easy to draw erroneous conclusions by comparing the percentages under different standards together. If the procurement document only says 'efficiency ≥99.9%' without specifying the standard and particle size, this sentence itself cannot be verified.

Why do we need both in the system?

For a complete clean air supply system, the division of labor between the front end and the end is clear.

The front filter bears most of the dust load. Coarse particles, fibers, and larger dust in the air are intercepted first. This part has high maintenance frequency and the replacement cost is relatively controllable.

The end filter provides the final fine control. ULPA blocks the remaining fine particles here to ensure that the air sent to the process area meets the standards.

What will happen if the ULPA is placed directly in a high dust location? The filter element is quickly filled with particles, the resistance increases, and the frequency of replacement increases significantly. This is not because ULPA is not easy to use, but because the end filter is placed where it should not be. This kind of problem is very common in projects where the front-stage protection is not in place. For specific troubleshooting ideas, please refer to the instructions related to the increase in filter pressure difference.

Common misunderstandings when replacing

The most common problem in actual projects is that 'it can be installed' as if 'it can be used'.

The medium-efficiency filter at the front of the unit and the ULPA at the end of the equipment are sometimes similar in appearance and size, and can even be stuffed into the same frame. However, the structural strength, sealing method, resistance characteristics and testing requirements of the two are different. After it is installed, a series of problems such as loose pressure, air leakage, and deviation of the fan's working point may occur.

To determine whether it can be replaced, at least check these items: the resistance at the rated air volume, whether the sealing structure matches, the pressure-bearing capacity of the installation frame, and whether the air volume of the replaced system is still within the design range. involving FFU fan filter unit or When the fan filter unit on the EFU equipment side is used together, the working points of the fan of the unit must also be checked together.

What should you compare when choosing?

Not all locations require ULPA, nor is it a waste to use ULPA in all locations. The judgment is based on process objectives and verification requirements.

You need to look at the full cost, not just the purchase price. In addition to the price of the filter element itself, it is also necessary to check the operating energy consumption corresponding to the resistance, fan matching, space for testing and element replacement. When ULPA resistance is high, long-term operating costs may be more worthy of attention than the purchase price difference.

The level of filtration should serve the process objectives. Upgrading all locations uniformly is neither economical nor necessarily solves the problem - the root cause of some substandard cleanliness lies in sealing or air flow organization, and improving the filter element level will provide limited improvement. For the rationality of front-end configuration, please refer to Consider HEPA/ULPA air filter selection information together.

Project judgment example

When particle control in a certain equipment becomes unstable, the first reaction is to change the terminal filter element from HEPA to ULPA.

However, after investigation, the problem was that the front-stage filter section had not been maintained for a long time, and the dust load was directly pressed to the end. After the ULPA was installed, the resistance rose rapidly, and the air volume decreased instead. In this case, the right direction is to resume front-level maintenance first, confirm the system air volume, and then evaluate whether it is necessary to upgrade the level.

Selection and Acceptance Checklist

About Aili Industrial’s filtering configuration support

The matching of ULPA and ordinary filters is essentially a matter of system division of labor. If the front-stage protection is done well, the burden on the terminal filter element will be light, and the replacement cycle will be more controllable.

Aili Industrial's manufacturing system covers filters, motors, fans, control systems and complete machine assembly, and can provide different levels of HEPA/ULPA air filters and supporting air supply equipment. For projects involving both the front-end filtration section and the end-end ULPA, the configurations at all levels can be checked together according to system conditions instead of selecting and installing one product separately.

Providing the target area, particle control requirements, design air volume and existing filter section configuration during the inquiry will help determine which stage needs to be adjusted. The specific configuration is subject to the technical documents and test results confirmed by the project.