How does the chemical filter size fit into the existing filter frame?

In renovation or replacement projects, we often encounter a situation: we already have a filter frame on site and want to directly switch to a chemical filter. I measured the length and width, and they felt about the same, so I thought it could be installed.

But just because it looks like it can be put in, doesn't mean it can be used. The matching of chemical filters is not only about the external dimensions, but also includes the sealing contact surface, pressing method, air flow direction, maintenance space and system resistance. If any of the items does not match, there may be a bypass after installation, the pressure may not be tight, the replacement may not be possible, or the gas treatment effect may not be up to standard. For specific structural forms, please refer to Discussion of the common product forms of chemical filters .

First measure the real installation interface

The first step in size verification is to clearly measure the actual interface on site, rather than just copying the old filter element label.

Frame clear opening. Measure the internal dimensions of the mounting frame, including length, width, and available depth. The depth must be deducted from the occupation of gaskets, pressing parts and frame structures to obtain the truly usable space.

Seal contact surfaces. Chemical filters may be sealed by gaskets, tanks, or other means. It is necessary to confirm where the corresponding contact surface on the frame is, how wide it is, and whether it is flat. The position of the gasket must correspond to the contact surface, otherwise it will not seal even if it is pressed up.

Holder position. Check the type, number and location of hold-downs on the frame. Does the structure of the chemical filter's outer frame allow for uniform application of force by these compression members? Can the compression point cover the entire length of the sealing surface? These must be confirmed before installation.

Condition of old filter element. If the old filter element is still there, you can observe its gasket position, airflow direction and installation marks as a reference. However, the old filter element may have been deformed or aged, so you cannot place an order directly based on its size. For specific measurement methods, please refer to Discussion of what dimensions should be covered for chemical filter retrofit field measurements .

Check load and resistance

After the dimensions are matched, it is also necessary to confirm whether the structure can withstand it and whether the system can drive it.

Weight and support. Chemical filters may have more media than older filters and may weigh more. Can the frame and support structure withstand it? If the weight increases, will the support need to be reinforced or adjusted?

Added resistance. Chemical filters usually have a different resistance than the old filter element. After replacement, the total system resistance will change and the fan operating point may shift. It is necessary to calculate whether the fan can still maintain the target air volume under the design air volume. For specific methods, please refer to Discussion of how much the added resistance of the chemical filter will increase the fan's electricity consumption .

Handle air volume. What is the air volume passing through this filter section? Is the passing wind speed of the chemical filter within a reasonable range at this air volume? An air volume that is too high may affect the treatment effect, and an air volume that is too low may result in insufficient processing capacity. For specific selection 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 .

Filter capacity. When space is limited, the number of media that can be installed is limited. It is necessary to check the target gas, inlet concentration and replacement cycle to confirm whether this capacity can meet the requirements. Just because it can fit in doesn’t mean the plan is valid. For specific life assessment, please refer to Discussion of how long chemical filters last .

Review sealing after installation

Installing it is just the beginning, and the sealing status needs to be verified in practice.

Check bezel fit. Does the outer frame of the filter element fit tightly with the frame? Are there any obvious gaps on the four sides and corners? Is the gasket or tank continuous?

Check the compression uniformity. Are the pressing parts evenly stressed? Is there a single corner that is compressed first, causing the outer frame to warp? Is the pressing force within a reasonable range and not too loose or too tight?

Check the access door seal. If the filter section has an access door, are the door frame seals intact? Is it tight after closing? Air leakage at these locations will also affect outlet concentration.

Bypass inspection. If the system permits, a simple smoke or pressure check can be done to confirm that there is no obvious bypass. For projects with higher requirements, leak detection is carried out according to the plan. For specific seal inspection, please refer to Discussion on how to check frame bypass after chemical filter installation .

Maintenance space and replacement paths

Size matching also requires subsequent maintenance.

Remove the filter element and make space. When replacing, the filter element needs to be removed from the frame. Are there any pipes, cables, or structural parts blocking the removal path? Is there enough operating space? If other parts must be removed for each replacement, maintenance costs will increase.

Installation direction. Chemical filters may have airflow direction requirements. Is it easy to confirm the direction during installation? Are there any markings or structural features to help determine this? If the direction is reversed, the processing effect may be affected. Please refer to the specific directions to confirm Discussion on whether the transportation direction and installation direction of chemical filters must be consistent .

Sampling and maintenance interface. If the project requires testing outlet concentration, is the location of the sampling port convenient? Is it possible to access the front and rear of the filter section during maintenance? These should be reserved in the renovation plan. involving MAU box chemical filter or For FFU systems equipped with chemical filters , the interface locations need to be checked together.

Project judgment example

In a factory renovation project, the original filter frame was equipped with an ordinary particle filter, which was planned to be replaced with a chemical filter.

Preliminary measurement: The length and width are close, so I think they can be replaced directly. However, further inspection revealed that the original frame's compression parts only covered the four corners, and there was no compression point in the middle. The sealing gasket of the chemical filter needs to be pressed continuously throughout the entire length. Pressing at the four corners cannot ensure the middle seal. At the same time, the resistance of the new filter element is about 30% higher than that of the original filter element. If the original fan has insufficient margin, the air volume will decrease.

Adjustment plan: Add a compression point in the middle of the frame to ensure uniform stress on the sealing surface; after calculating the fan working point, select a chemical filter structure with a larger effective filtration area to reduce resistance. After installation, check the seal point by point and measure the air volume to confirm that the system is operating normally.

This case illustrates: Dimensional matching is only the first step, sealing, compression, resistance and maintenance must all be checked together. involving When selecting a chemical filter product series , it is recommended that the frame drawings, installation conditions and target gases be provided to the supplier for verification.

Key points for selection and acceptance inspection

About Aili Industrial’s frame matching support

The core of matching the chemical filter to the existing frame is to match the size, sealing, resistance and maintenance conditions.

Aili Industrial has independent manufacturing capabilities in filters, motors, fans, control systems and sheet metal processing, and can provide chemical filter product series and supporting air supply equipment. For retrofit or replacement projects, frame drawings, installation conditions, target gases, and system air volumes can be combined to assist in checking filter size, sealing methods, and structural configuration. When the filter is matched with MAU, FFU, EFU and other equipment, the interface, resistance and maintenance methods can be confirmed uniformly.

Related products:Chemical filter product series、MAU box chemical filter、FFU comes with chemical filter . Provide frame dimensions, installation conditions and system parameters when inquiring to help confirm a suitable matching solution. The specific selection is subject to the technical documents and test results confirmed by the project.