How to troubleshoot abnormally high initial resistance of ULPA?

The new filter element was installed, and the differential pressure gauge reading was much higher than expected. At this time, there are usually two reactions on site: either suspecting that there is a problem with the product, or thinking of increasing the fan speed to overcome it. Both of these approaches are not appropriate until the reasons are clear.

The initial resistance is abnormally high, which may be due to the product itself, or to the measurement method, installation status or system conditions. Check them in order first, and then decide how to deal with them.

Check the measurement range first

If the differential pressure gauge shows a high level, don’t blame it on the filter element. There may be problems with the measurement process itself.

Is the pressure pipe blocked or wrongly connected? The pipelines on the high and low pressure sides are connected reversely, the pressure inlet is blocked, and the pressure guiding tube is bent, which will cause the reading to deviate from the actual value. Check whether the pipeline is smooth and the connection is correct.

Are the measuring point locations consistent? What two points does differential pressure measure? If the measurement point is mixed with box loss, air duct resistance or pressure drop of other components, the reading will naturally be higher. The pressure difference on the filter element body and the pressure difference on the whole machine should be distinguished. For specific measuring point setting methods, please refer to the relevant instructions for differential pressure measuring points.

Is the instrument normal? The zero point, range and calibration status of the differential pressure gauge must be confirmed. If the readings of differential pressure gauges in other locations in the same system are normal and only this one is abnormal, the possibility of a problem with the instrument itself also needs to be considered.

Does the air volume working condition correspond? What is the current operating air volume? At what air volume was the initial resistance on the report measured? If the on-site air volume is significantly higher than the test air volume, the pressure difference will naturally be high. Align the working conditions first, and then look at the numerical differences.

Check filter element and installation status

After the measurement link is confirmed to be correct, the next step is to look at the filter element itself and its installation.

Do the model and specifications match? Is the one installed corresponding to the quoted price? Are the thickness, structure, and filter media type consistent? Sometimes models with similar appearance are mixed and the resistance characteristics may be different.

Have the packaging films been removed cleanly? Some filters come with a protective film or packaging material that needs to be completely removed before installation. Residual film can significantly increase drag.

Is the installation direction correct? Installing it backwards may cause the airflow path to change and the resistance may be abnormal. To determine the direction, please refer to the instructions related to the inlet and outlet wind directions.

Is the installation in place? Is the filter element completely seated within the mounting frame? Does the sealing surface fit well? Are the pressing parts pressed evenly? Installation deflection may lead to higher local wind speeds and overall resistance will also be affected.

Whether the filter material is damp or damaged. If it gets damp during transportation or storage, the resistance of the filter material may change. Deformation of pleats and local indentations may also affect airflow.

Is there any obstruction upstream? If there are foreign objects, packaging debris or other structural parts in front of the filter element blocking part of the ventilation surface, it is equivalent to reducing the effective area and the resistance will increase. Supporting The system of the FFU fan filter unit , the air inlet and internal channels of the unit must also be inspected; equipment-side applications such as The EFU equipment-end fan filter unit has a compact internal space, and the occlusion problem requires more attention.

How to arrange retesting with suppliers

If no problems are found during on-site inspections, or if there are questions about the product itself, retesting can be arranged.

Unify test conditions. Make it clear which air volume, which method and which points to measure. The test conditions must be aligned with the conditions on the report, otherwise the retest results will still be incomparable.

Keep the original reading. The pressure difference measured on site, the corresponding air volume, fan gear and environmental conditions must be recorded. This data is the basis for subsequent communications.

Associated product number. The retest should correspond to the specific filter element and record the serial number or batch number.

Provide complete information to suppliers. Includes field measurement data, installation photos, system conditions. After the supplier receives this information, it can compare it with the product curve to determine whether the difference is within a reasonable range.

If the retest still exceeds the agreed value, it will be handled according to the technical agreement. The treatment method may include replacement, adjustment or other agreed solutions, rather than simply increasing the speed to overcome it. involving HEPA/ULPA air filters have the same troubleshooting methods, and the criteria are implemented according to the corresponding standards. Products of different grades of

Project judgment example

After a U15 filter element was installed in a piece of equipment, the differential pressure gauge reading was nearly twice as high as the original H14.

The investigation found that the on-site measurement was the pressure difference between the inlet and outlet of the box, which included the resistance of the internal channel and diffuser plate of the box, while the data in the report was the pressure difference on the filter element body. The two measuring points are different, and the values ​​cannot be directly compared.

After adjusting the measuring points to the front and rear of the filter element, and re-measurement, it was found that although the pressure difference on the filter element body was high within a reasonable range, it did not reach an abnormal level. Further verification revealed that the on-site air volume was slightly higher than the design value, which also explained part of the difference.

The treatment direction is to adjust the air volume to the design working condition and then retest, rather than changing the filter element or increasing the rotation speed. involving For the selection of ULPA ultra-high efficiency filter , please refer to the corresponding product information.HEPA high-efficiency filter is the same. The resistance check method of

Selection and Acceptance Checklist

Regarding Aili Industrial’s cooperation in resistance investigation

To troubleshoot abnormal initial resistance, it is necessary to compare on-site data and product parameters together.

Aili Industrial's manufacturing system covers filters, motors, fans, control systems and complete machine assembly, and can provide HEPA high efficiency filter、ULPA ultra-high efficiency filter and supporting air supply equipment. filter with FFU fan filter unit、When the EFU equipment-end fan filter unit is matched, the filter element resistance and fan operating point can be calculated together in the planning stage to facilitate comparison and judgment during operation.

When encountering abnormal initial resistance on site, it is recommended to record the air volume, measuring point location and product number first, and then contact the supplier for verification. The specific handling method shall be subject to the on-site inspection results and project agreement.