What will be the impact if the wind speed facing the filter is too high?

The filter head-on wind speed is the average speed of air passing through the front of the filter. It is directly related to air volume and filter area. When many sites encounter insufficient air volume, they will increase the air supply by increasing the fan speed. However, if the filter area is not checked simultaneously, the oncoming wind speed will increase, causing increased resistance, increased power consumption, increased noise, and even affecting the life of seals and filter materials.

Excessive headwind speed does not necessarily improve cleanliness protection, but may cause the system to deviate from the original confirmed operating conditions. The following will start from the aspects of area diameter, resistance change, sealing effect, and air volume distribution.

Heading wind speed should be calculated using the correct area

The head wind speed is usually calculated by dividing the actual air volume passing through the filter by the corresponding windward area. It should be noted here that the front area of ​​the filter is different from the unfolded area of ​​the folded filter material. Using the wrong area can lead to numerical distortion.

For specific conversion methods, please refer to How to convert face wind speed and air volume? , area diameter can be referred to How should we look at the effective air outlet area of ​​FFU? . If calculated only based on the box outer area, the actual head-on wind speed may be underestimated.

Too high head wind speed will push up the filter resistance

Filter resistance is related to head wind speed. As wind speed increases, the pressure drop caused by the filter material and structure usually increases. On a given fan curve, an increase in system resistance will shift the operating point, and the air volume may decrease instead of rising.

If the filter area is insufficient, the fan will require higher pressure to maintain flow. For specific impacts, please refer to How does insufficient filter area affect fan selection? . If you only increase the speed without checking the operating point, you may enter an inefficient operation zone.

Impact on efficiency and sealing conditions

Filter efficiency is confirmed under specified test conditions. If the head-on wind speed is too high, the operating conditions of the filter may exceed the original confirmation range and affect the efficiency performance. At the same time, a higher pressure difference will act on the frame, sealing strips and installation interfaces, increasing the risk of bypass leakage.

If there are abnormal particles on site but the filter efficiency is acceptable, priority should be given to checking the sealed bypass and airflow short circuit. Can be referenced What particle problems can airflow short circuits cause? and What should be checked when cleaning equipment is accepted?。

Power consumption, noise and filter material life

An increase in head-on wind speed is usually accompanied by an increase in fan speed and input power, and the noise may also become louder. Long-term high wind speed operation will increase the load on the filter material, which may affect the service life.

When comparing operating costs, the input power of the complete machine under the same load should be used, and calculated separately based on actual work and duty hours. Rated power cannot be used directly to calculate annual expenses. For details, please refer to What is the difference between FFU rated power and actual power consumption?。

Air volume distribution and system balance

When multiple filters are running in parallel, if the head-on wind speed of each filter is very different, uneven distribution of air volume may occur. The wind speed of some filters is too high, the resistance increases, and the air volume decreases; the wind speed of other parts is too low, and the capacity is not fully utilized.

When debugging the system, the air volume and pressure difference of each filter should be measured, and the air valve or operating settings should be adjusted if necessary. If multiple devices require partition duty and troubleshooting, they can be combined FFU group control system provides unified management.

The relationship between rated air volume and actual operating air volume

The rated air volume of the filter is used to describe its specified test or design conditions. The actual operating air volume should fall within the usage range confirmed by the manufacturer. If the actual air volume is significantly higher than the rated value, the headwind speed may exceed the recommended range.

For specific judgment, please refer to How does the rated air volume of the filter match the actual operating air volume? . If you are not familiar with the reading of working point with filter, you can read Why should we look at the complete performance curve when selecting FFU? and Is FFU's nominal air volume tested with a filter?。

The solution is not just to reduce the speed

When the head-on wind speed is too high, you can deal with it from several directions:

• Increase the filtration area : choose a model with a larger windward size or more filter elements;

• Optimize the filter element structure : select low-resistance filter material or reasonable folding structure under the same appearance;

• Distribute the air supply load : increase the number of air supply units and reduce the air volume of a single unit;

• Adjust the working point of the fan : reduce the rotational speed on the premise of meeting the air volume of the workstation;

• Improve air path distribution : reduce local short circuits and resistance concentration.

After reducing the speed, it is still necessary to verify the airflow coverage of the workstation to avoid solving the resistance problem but leaving insufficient protection. For relevant judgments, please refer to Is excessive FFU air volume good for cleanliness?。

Filter thickness and resistance are not simply corresponding

Increasing filter thickness does not necessarily reduce resistance. The pressure drop is determined by the characteristics of the filter material, folding structure, filter area, air volume and internal support. Specific model data under the same working conditions should be used for comparison. Resistance or service life cannot be inferred from appearance thickness. Related analysis can refer to Does increasing filter thickness definitely reduce resistance?。

Heading wind speed under initial resistance and final resistance

The initial resistance usually describes the pressure drop of a new filter under a specified air volume, and the final resistance is used to judge maintenance or replacement during the agreed use period. When selecting the model, the operating points at the initial resistance and final resistance should be confirmed to ensure that the head wind speed is within a reasonable range during the entire service life.

For specific judgment, please refer to What are the initial resistance and final resistance used to judge? . If the operating pressure differential is abnormally low, a breakage or bypass should be investigated rather than a performance improvement.

Equipment selection and terminal matching

Filter selection should correspond to target particle size and actual resistance.The HEPA and ULPA filter pages have parameters for different levels of products. When selecting, check the efficiency of the specific model at the target air volume. If you are still unclear about how HEPA and ULPA match the goals, you can read How do HEPA and ULPA match cleanliness goals? . To choose between different levels, please refer to How to choose between H13, H14 and U15?。

Please refer to the room background air supply FFU clean air supply products , please refer to the local protection of the equipment side. EFU equipment side fan filter unit . The logic of division of labor between the two lies in The division of labor between device-side EFU and room FFU is explained in detail.

If it involves sealing the equipment cavity, please refer to How to plan clean air supply for closed equipment cavities? , first confirm the cavity boundary and airflow path. When it comes to ceiling installation, please refer to How does the FFU appearance size match the ceiling module?。

Project judgment example

In a certain project, in order to increase the wind speed at the workstation, the FFU speed was increased. After operation, it was found that the filter pressure difference increased, air leakage occurred in some frames, and power consumption and noise also increased. The investigation found that the original filter area was too small and the headwind speed exceeded the recommended range. Adjustment method: Change to a model with a larger filter area, reduce the air volume of a single unit, and re-tighten the seal. After adjustment, the wind speed at the workstation became stable, and the pressure difference and noise were restored.

In another project, multiple filters were connected in parallel. The wind speed facing some equipment was too high and some was too low. Adjustment methods: Rebalance air volume distribution, adjust dampers and operating settings. After adjustment, the operating conditions of each filter tend to be consistent.

These two situations illustrate that too high a wind speed facing the filter will cause resistance, sealing and energy consumption problems, which should be dealt with comprehensively in combination with the filter area, fan operating point and system distribution.

Key points for selection and acceptance inspection

Aili industrial equipment supporting support

If the head wind speed is too high, it often cannot be solved by changing the filter alone. It involves filter area, filter material structure, fan working point, sealing conditions and air volume distribution. Aili Industrial has collaborative capabilities in air filter manufacturing, fan independent research and development, control systems and complete machine assembly. It can check the filter area, initial and final resistance, fan speed and power based on the project target air volume and allowable headwind speed to help determine whether to increase the filter area, adjust the fan working point or reallocate the air path. Specific filter parameters can be viewed HEPA and ULPA filters , the complete machine package can be viewed FFU clean air supply products and EFU equipment side fan filter unit。