How to check the effective treatment area of ​​small-sized EFU chemical filters?

The filter section of small-sized EFU is often only the size of a palm or smaller. The internal space of the equipment is tight, and the disassembly and assembly openings are also limited. After installing it, it is necessary to ensure that the gas treatment, air volume and sealing can be established.

At this size, the effective processing area is particularly prone to overestimation. Some people directly use the length times the width of the filter element frame as the processing area, while others directly apply it according to the rated air volume of a single unit on the sample. The actual area of ​​air passing through, the amount of media that can be filled, and the airflow distribution inside the equipment will all affect the treatment effect. Checking these conditions clearly is more important than just looking at the dimensions.

First distinguish the shape and flow area

The effective treatment area refers to the area of ​​the filter material that air can actually pass through, not the outer frame size.

The outer frame area includes the frame, sealing edge, supports and installation structure. These parts do not participate in gas treatment and should be deducted when calculating the flow area. In a small-size EFU, the frame and sealing structure may account for a higher proportion, and the effective area after deduction will be significantly smaller than the outer frame area.

Porous or folded structures must also be understood according to the product definition. Some chemical filter media are folded, and the unfolded area and the windward area are not the same value. If the area definition is given in the product information, you should confirm whether it refers to the effective windward area or the expanded area of ​​the filter material. The two cannot be mixed. For specific product forms, please refer to the chemical filter product range . Description of

Document occupancy of supports and shelters. There may be flow equalizing plates, protective nets, and fasteners inside small-sized EFUs, which will further reduce the actual flow area. When measuring and checking, it is recommended to record the net flow size in the installed state instead of just measuring the filter element itself.

Determine flux based on air volume

After the effective area is determined, it should be considered together with the actual air volume.

The air volume and effective area jointly affect the passing wind speed. Under the same air volume, the smaller the effective area, the higher the passing wind speed. When the wind speed is high and the contact time between the gas and the medium is short, the treatment effect may decrease and the resistance may also increase. For specific calculation methods, please refer to Discussion on whether the chemical filter air volume should be selected based on the total air volume of the system or the air volume of a single unit .

The rated air volume of small-sized filter elements cannot be directly applied. Single unit data on the sample usually corresponds to specific dimensions, media and pressure loss conditions. If the effective area under actual installation conditions is smaller than the sample conditions, the performance under the same air volume will be different.

Check the data for the target gas at this flux. If the supplier provides the efficiency, capacity or penetration curve of the target gas, it should be confirmed whether the corresponding air volume, area and installation conditions are close to the project. If the conditions are far worse, the reference value of the data will be limited. For specific report interpretation, please refer to Discussion of why chemical filter performance reports list specific target gases .

Check the bias flow in the equipment

The airflow distribution inside the equipment will affect the utilization of the effective area.

When the inlet is close to the edge, the airflow may be deflected to one side. If the air inlet position of a small-sized EFU is offset, the air volume in the filter material area close to the inlet may be larger, and the air volume in the area far from the inlet may be small. The average wind speed looks normal, but may be higher or lower in places.

Blockage of pipelines, covers or structural parts can also cause biased flow. If there is partial obstruction in front of the filter material, the actual area participating in the flow will be reduced. This reduction is not necessarily reflected in form factor, but affects handling and drag.

Combined with the airflow distribution verification, you cannot just calculate the average value. After installation, the wind speed can be measured at multiple points before and after the filter material or on the air outlet surface to determine whether the air flow is uniform. involving The overall solution of the EFU equipment end fan filter unit , the internal structure of the equipment and the air flow path need to be checked together.

Installation interface and maintenance

Small-sized filter sections also need to check sealing and replacement conditions.

The sealing surface cannot be ignored. If the sealing gasket or slot between the filter element and the box is not pressed tightly or is misaligned, air may bypass the frame. No matter how large the effective treatment area is, sealing problems will also affect the outlet concentration. For specific inspection methods, please refer to Discussion on how to check frame bypass after chemical filter installation .

The replacement space must be confirmed during design. The small size EFU is compact internally, and other components may need to be disassembled when replacing the filter element. Maintenance access and operating space must be confirmed during the planning stage to avoid being unable to fit in or replace them.

Recheck after replacement. After replacing the filter element or adjusting the filter section, it is recommended to re-confirm the air volume and outlet concentration. Small-sized systems often have little margin, and the difference before and after replacement may be more obvious than in larger systems.

Project judgment example

The EFU of a certain equipment needs to add a chemical filtration section in a limited space, and the two small-sized filter elements that are candidates have similar shapes.

In the initial comparison, just looking at the external dimensions, both models can fit in. However, further inspection revealed that one model has a wider frame and takes up more internal supports, and its actual effective flow area is about 20% smaller than the other model. Under the same air volume, the first model has a higher passing wind speed and greater resistance.

Adjustment plan: Choose one with a larger effective area, and check the position of the air inlet inside the device to prevent the airflow from deflecting to one side. After installation, measure wind speed distribution and outlet concentration to confirm that targets are met. The filter replacement cycle is also recorded based on actual operating data.

This case illustrates: When checking the effective area of ​​a small-size EFU, you must look at the net flow area, not just the appearance. For device-side filtering configuration, please refer to The matching idea of ​​FFU matching chemical filter is combined with the confirmation of equipment structure.

Key points for selection and acceptance inspection

About Aili Industrial’s small size filter section package

The chemical filtration section of the small-sized EFU often does not just need to be installed in a ready-made size. The internal space, air ducts, maintenance ports and gas indicators of the equipment should be looked at together.

Aili Industrial has independent manufacturing capabilities in filters, fans, control systems and sheet metal processing. It can discuss the flow area, interfaces and sealing methods of small-sized chemical filtration sections in conjunction with equipment drawings. If you already have a prototype or old filter element, you can also check the configuration against the actual dimensions and operating data. Related products can be viewed Chemical filter product series , specific selection shall be subject to the technical documents and test results confirmed by the project.