How to check the target wind speed after the FFU is equipped with a chemical filter?

After installing a chemical filter, changes in wind speed cannot be judged by hand feel. It is necessary to measure the outlet wind speed at the specified measuring points at the same operating gear, and then compare it with the baseline or design value before modification. If you only look at 'the wind seems to be smaller', or only look at the total air volume as a number, it is easy to confuse local bias flow, seal bypass or fan operating point changes.

First, measure the baseline before the transformation

If wind speeds are not recorded before the retrofit, there will be no baseline for comparison after the retrofit.

The baseline content includes: wind speed distribution on the original air outlet surface, unit gear position, filter status, environmental conditions, measuring instruments and measuring point locations. The measurement methods must be consistent, otherwise the data before and after the transformation will not be comparable.

If the original FFU particle filter has accumulated dust, record the pressure difference and operating time to avoid taking the resistance of the old filter element as new. For equipment-side applications or modification projects, it is recommended to complete a baseline measurement before construction.

The wind speed on the outlet surface should be measured according to the measuring point

Wind speed verification does not only measure the center point.

Divide measuring points into equal areas. The air outlet surface is divided into several areas, each area represents a representative point, and the average value after stabilization is read. The measuring point location, probe distance and measurement time should be recorded.

Focus on uniformity. After the chemical filter section is installed, the air outlet surface may be partially higher or lower due to changes in the internal structure. If the wind speed deviation at different locations of the same FFU is obvious, it is necessary to check the installation status, sealing and flow equalization structure of the filter section. For specific installation inspection, please refer to Discussion on how to check frame bypass after chemical filter installation .

Different gears are recorded separately. If the FFU has a working gear and a duty gear, the wind speed in both states must be confirmed. The operating parameters may change after modification, so you cannot only measure one gear.

The resistance change should be put into the fan operating point

Chemical filtration sections increase resistance. If the original fan is at the same gear, the air volume may decrease.

How much it drops depends on: chemical filter section resistance, original fan curve, and other system resistance. The impact cannot be judged solely by the thickness of the chemical filter section. For specific accounting methods, please refer to Discussion of how much the added resistance of the chemical filter will increase the fan's electricity consumption .

The terminal air volume cannot be lower than the design range. If the FFU serves a clean area or inside equipment, reduced air speed may affect airflow coverage and particle control. When calculating, it is necessary to confirm that the air volume corresponding to the target wind speed still meets the requirements.

When multiple FFUs are connected in parallel, the air volume distribution may change. After the chemical filter section is installed, the resistance of each unit is different, and the air volume distribution may deviate. Measure the wind speed one by one and adjust the gear or damper if necessary.

When adjusting the operating gear, review other indicators

If the air volume is insufficient, it is common practice to increase the rotation speed. But when the speed increases, other indicators will also change.

Motor and controller allowable ranges. Current, power, noise and vibration may increase. It is necessary to confirm that these parameters are within the allowed range.

Gas treatment effect. After increasing the wind speed, the contact time between the gas and the chemical medium is shortened. If the outlet concentration rises, it is necessary to evaluate whether to adjust the filter section configuration. For specific effect verification, please refer to Discussion of sampling points for chemical filter performance verification .

Particle cleanliness. If the FFU was originally responsible for particle control, the particle cleanliness cannot be reduced after the transformation. Leak detection and particle detection shall be carried out according to the original requirements. Can be referenced HEPA high-efficiency filters . Testing instructions for

Gas treatment effects or particle control cannot be ignored in order to restore wind speed. Both need to be satisfied at the same time.

Seal bypasses can distort wind speed data

If the border of the chemical filter section is not tightly sealed and some air bypasses the media, the wind speed on the outlet surface may appear to be normal, but the gas treatment effect will be reduced.

When checking the wind speed, it is recommended to also check: the installation interface of the chemical filter section and the particle filter, the status of the sealing gasket, and the distribution of the pressing parts. If the bypass is found, deal with it first, and then re-measure the wind speed.

The gas outlet concentration should also be confirmed. Qualified wind speed does not mean that gas treatment is up to standard. The two are verified separately and the records are filed separately.

Record new baseline

After the adjustment is completed, record the new operating data.

Record content: wind speed distribution, operating gear, pressure difference, outlet concentration, environmental conditions. These data serve as a baseline for subsequent maintenance.

After replacing the chemical filter section or particle filter, it is recommended to retest under the same conditions. The system margin on small-sized devices is limited, and the difference before and after replacement may be more obvious than in large systems. involving The FFU supporting chemical filter system, interfaces and maintenance methods can be confirmed at the planning stage.

Project judgment example

After a certain FFU was equipped with a chemical filtration section, the operator felt that the air volume became smaller and directly increased the rotation speed from 60% to 80%. The wind speed in the center of the outlet surface recovered, but the edge wind speed was still low.

The inspection found that the sealing gasket at one corner of the chemical filtration section frame was displaced, causing a partial bypass; at the same time, the unit noise increased significantly after increasing the speed. The treatment method is to restore the seal, retest at the original gear, and confirm that the wind speed distribution meets the requirements before determining the operating parameters.

This example illustrates: To check the wind speed, you need to measure the distribution, check the seal, and look at the working point, not just adjust the speed.

Key points for selection and acceptance inspection

About Aili Industrial’s FFU chemical filtration package

Aili Industrial has independent manufacturing capabilities in filters, fans, control systems and sheet metal processing, and can provide chemical filter product series and supporting air supply equipment. For FFU installation of chemical filtration section or complete machine supporting projects, we can assist in checking the configuration and interface of the filtration section based on the target gas, original unit parameters, installation space and wind speed requirements.

Related products:Chemical filter product series、FFU comes with chemical filter . The specific selection is subject to the technical documents and test results confirmed by the project.