What should I do if the noise or howling increases after ULPA upgrade? Airflow and structural troubleshooting

If the noise or whistling increases after the ULPA filter is upgraded, the fan speed, operating point, airflow narrowing and structural vibration should be compared. Sound changes may be related to increased resistance and speed, but the quality of the filter element cannot be judged by hearing alone. There are two typical sources of noise changes after the upgrade: one is aerodynamic, when the airflow speed increases when passing through denser filter materials or narrower gaps, resulting in high-frequency whistling; the other is structural, where the fan load changes after the resistance increases, or the installation state changes, resulting in vibration and resonance. The two sources have different processing directions. First distinguish the sources and then decide on the direction of adjustment. Aili Industry isFFU fan filter unit andIn the matching of the fan filter unit at the EFU equipment end , the fan speed, working point and filter resistance data come from the same system. The operating parameters before and after the upgrade can be compared, and when the noise changes, it can be determined whether it is aerodynamic factors or structural factors.

1. Check the conditions before and after the upgrade: comparison is only meaningful under the same air volume

Record the model, air volume, pressure difference, rotation speed and control method to confirm whether the noise increases at the same air volume or is generated after speed adjustment.

After upgrading, if the rotation speed is increased in order to maintain the air volume, the increase in noise may only be the result of the increase in rotation speed and has nothing to do with the filter element itself. If the air volume and rotation speed are the same, but the noise increases significantly, you need to check the filter material structure or installation status. Aili Industry isIn the HEPA/ULPA filter upgrade plan, check the working points before and after the upgrade according to the target air volume.The FFU computer group control system records speed, air volume and pressure difference parameters, and the data before and after the upgrade can be directly compared. The relationship between levels and filtering requirements can be found inISO cleanliness level comparison。

2. Locate aerodynamic and structural sound sources: howling, resonance and friction should be separated

Check the inlet obstruction, sealing gap, protective net, fastening and fan operating status to distinguish whistling, resonance and component friction.

Aerodynamic noise usually manifests as continuous high-frequency whistling, and the sound source is in the narrow part of the airflow channel: the gap between the inlet and the structure, the gap between the sealing strip and the box, and the seam between the edge of the filter material and the frame. Structural noise manifests as low-frequency vibration or intermittent sound, which may be caused by loose fasteners, unbalanced fans, or resonance between the box and the ceiling. Aili Industry isThe box structure of the fan filter unit at the EFU equipment end has process requirements for the inlet and sealing gap.The complete test of the FFU fan filter unit will check the balance and fastening status of the fan. If the noise is abnormal, it can be checked from the aerodynamic and structural directions. The relationship between sealing gap and noise can be referred toHEPA FAQs and Selection Guide。

3. Adopt targeted adjustments: check the air path first and then move the structure

Check the air volume target before rectifying the air path or structure to avoid excessive reduction in speed to eliminate sound but lose protection. After adjustment, re-measure the air volume and related performance at the same time.

If the sound source is in the air path, adjusting the inlet direction, expanding the airflow channel, or changing the sealing state may be effective; if the sound source is in the structure, retightening the fasteners, correcting the fan balance, or adding vibration reduction measures are the best directions. No matter what kind of adjustment, it must be based on maintaining the target air volume. Aili Industry isnon-standard ULPA filter upgrade project, the adjustment plan is evaluated according to the original system conditions.In the The FFU fan filter unit supports EC DC speed adjustment, and the operating parameters can be set according to the target air volume after adjustment;Compact models such as ultra-thin EFU consider the balance between airflow channels and noise in the structural design. Please refer to the adjusted verification method.ULPA ultra-high efficiency filter FAQ and selection guide。

4. When there is whistling from the local gap in the frame, the sealing and stress should be checked.

When there is whistling from a local gap in the frame, the sealing and stress should be checked. Do not just put sound-blocking materials on the outside. The whistling indicates that there is high-speed airflow passing through the narrow gap. The root cause is discontinuous sealing or insufficient pressing force.

Aili Industry isThe supporting instructions for the liquid tank seal ULPA filter and the mechanical compression structure clearly specify the sealing surface status and compression requirements. When gap whistling occurs after the upgrade, check from the three aspects of seal position, compression sequence and frame flatness, instead of covering it up with sound insulation materials. For the relationship between sealing status and noise, please refer toHEPA FAQs and Selection Guide。

5. Related questions and answers

Will it be solved if the speed is reduced and quieter?
It is also necessary to confirm that the air volume, uniformity and process protection are not lower than the requirements.

Is the increase in noise after the upgrade necessarily a quality issue with the filter element?
uncertain. Increases in rotational speed, changes in air flow channels, and changes in installation status may lead to changes in noise. The operating conditions before and after the upgrade should be compared.

How to deal with the howling at the border gap?
The sealing continuity and pressing force should be checked, and the problem should be solved starting from the sealing state. Don't just apply sound insulation materials on the outside.

6. Related articles

ULPA ultra-high efficiency filter FAQ and selection guide

Ultra-thin EFU

Liquid tank seal ULPA ultra high efficiency filter

FFU FAQ and technical support

7. Key points for selection and acceptance inspection

8. Product matching and technical support from Aili Industrial

Aili Industry isFFU fan filter unit andIn the matching of the fan filter unit at the EFU equipment end , the fan speed, working point and filter resistance data come from the same system. The operating parameters before and after the upgrade can be compared. When the noise changes, it can be judged whether it is aerodynamic factors or structural factors.The HEPA/ULPA filter upgrade plan checks the front and rear working points according to the target air volume.The FFU computer group control system records speed, air volume and pressure difference parameters;The box structure of the fan filter unit at the EFU equipment end has process requirements for the inlet and sealing gap.The complete test of the FFU fan filter unit checks the balance and tightening status of the fan.The non-standard ULPA filter upgrade project evaluates and adjusts the plan based on the original system conditions.The FFU fan filter unit supports EC DC speed regulation and sets operating parameters according to the target air volume after adjustment.Ultra-thin EFU balances airflow channels and noise in structural design.The supporting instructions for the liquid tank seal ULPA filter and mechanical compression structure clarify the sealing surface status and compression requirements. Provide process objectives, installation drawings, operating conditions and acceptance requirements, and can further communicate ULPA standard specifications, non-standard interfaces, samples and batch matching. The specific parameters and test range are based on the confirmed model and technical documents.