How to determine the air inlet and outlet direction of ULPA filter?

Reverse installation is not very common at the end of the suspended ceiling. The air outlet faces downward and the direction is basically fixed. But inside the equipment, where the air path has a turning point, judging the direction is not so intuitive.

What’s even more troublesome is that the air inlet and outlet surfaces of ULPA sometimes don’t look much different in appearance. The protective screen, filter material color, outer frame structure, and different models have different designs. It is easy to make mistakes based on experience. Direction confirmation should be based on the manufacturer's logo, structural drawings and installation instructions, and cannot be inferred from appearance.

First check the logo and sealing position

Different models of ULPA may have different arrangements of protective nets, liquid tanks or gaskets. When judging the direction, confirm the correspondence between the arrow mark, the windward side and the clean side, and check whether the version of the installation diagram you have is consistent with the actual product.

You need to look at the logo, but you can’t rely on it alone. The protective net or sealing surface design of some products is symmetrical and can be installed front or back, but only one direction is correct. If the logo is obscured by packaging, worn, or the drawing version does not match, cross-validation based on structural characteristics is required.

The location of the gasket or liquid tank is usually on the air inlet side or the air outlet side, depending on the box design. The arrangement of the pressing surface and protective net can also provide directional clues. Comparing these features with the box structure is more reliable than just looking at the arrows. For the verification method of the liquid tank sealing structure, please refer to the instructions related to the knife edge size.

Confirm along actual airflow path

For ULPA inside the equipment, it is not enough to just look at the filter element itself, but also to go through the entire airflow path.

The starting point is the blower. Find the fan position of the air supply unit and confirm the air outlet direction. Then follow the air duct and diversion structure downwards to see which structural parts the airflow passes through, where it turns, and which side it finally enters the filter element from.

The air path inside the equipment is often not straight and may have diffusers, flow nets, or elbows. These structures will affect the direction of airflow and also affect judgment. Marking this path on the equipment drawing and comparing it with the actual assembly position is more reliable than inferring from experience. Device-side applications such as The internal structure of the EFU equipment-end fan filter unit is complex, so this step is particularly important.

Inspection after reverse installation and operation

If you find that it has been running for a period of time when it is installed upside down, you cannot just turn it over and reinstall it.

Record the operation history : how long it has been running with the installation reversed, the air volume, dust, temperature and humidity conditions during the period. This information can help determine how the filter has been affected.

Check the filter material and edge sealing : reverse installation may cause the stress state of the sealing surface to change, and the pressure direction of the filter material may also be different. Check whether the filter material has been pressed out, whether there are any abnormalities in the edge sealing glue, and whether the protective net has shifted.

Check the status of the gasket : the gasket that is pressed when installed upside down may have been deformed or displaced. If the gasket loses its resilience, continued use may not form an effective seal. For specific evaluation methods, please refer to the instructions related to gasket compression.

Don’t just flip it and pass it off. The condition of a filter element that has been operated is different from that of a brand-new one, and it needs to be judged based on the actual inspection results.

Rechecking needs to cover the installation interface

After the direction is corrected, reassemble according to the normal installation process, and then complete the re-inspection.

Air volume and pressure difference : Confirm that they are restored to the design range. Readings taken during reinstallation cannot be used as a baseline.

On-site leak detection : Scan the filter material surface and surrounding interfaces according to project requirements. Reverse installation and re-disassembly may change the sealing state. Leak detection is a necessary step to confirm whether the seal has been restored. involving For HEPA/ULPA air filter products of different grades, the testing requirements are implemented in accordance with corresponding standards.

Wind speed distribution : Confirm that the wind speed on the air outlet surface is even and there are no new problems caused by disassembly and assembly.

Record : Record the reasons for direction correction, inspection findings and retest results. For multiple devices of the same model, it is recommended to unify the recording format of the assembly direction to avoid subsequent maintenance personnel from making incorrect installations again.

Project judgment example

The old equipment did not have direction markings, and the installer judged the installation direction based on the appearance.

In this case, the correct approach is to first confirm with the supplier with physical photos and drawings, rather than inferring from disassembling the filter material. Disassembling the filter material will damage the product structure. Even if it is installed in the correct direction later, the state of the filter element itself has changed.

If it is a batch installation, it is recommended to confirm the direction at one location first, record the basis for judgment, and then process other locations in the same way. Supporting For the FFU fan filter unit system, the air flow direction inside the unit and the installation direction of the filter element must also be confirmed accordingly.

Selection and Acceptance Checklist

About Aili Industrial’s installation direction matching

Regarding direction confirmation, if the product leaves the factory with clear markings and complete drawings, there will be less trouble on site.

Aili Industrial's manufacturing system covers filters, motors, fans, control systems and complete machine assembly, and can provide ULPA ultra-high efficiency filter and supporting air supply equipment. filter with When the FFU fan filter unit and EFU are matched in the same system, the air flow direction, sealing surface position and assembly structure can be uniformly confirmed before leaving the factory, reducing problems caused by unclear directions on site.

When enquiring, provide the internal structure diagram of the equipment, the location of the fan and the available installation space, which will help confirm the basis for direction judgment. Specific installation requirements are subject to product descriptions and project technical documents.