Number of views: 5832 Author: Aili Industry Release time: 2027-06-24 Source: Ai Li Industrial
How to match ULPA and fan curve? Operating point and performance margin
The matching of ULPA filter and fan should determine the working point based on the system resistance curve composed of the filter element and other components, combined with the performance of the fan at the specified speed. The free air supply volume cannot represent the installed air volume. Working point matching is the most easily simplified step in selection: there is a maximum air volume on the fan sample, and a rated air volume on the filter sample. If the two numbers look similar when put together, the matching is considered complete. However, the actual operating point is the intersection point of the fan performance curve and the system resistance curve. When there is no accurate data on both curves, the intersection point cannot be determined. Aili Industry also produces fans, filters and complete machines.FFU fan filter unit andthe fan filter unit at the EFU equipment end come from the same system, and the working point calculation can be performed on the basis of complete data.The fan performance curve and filter resistance data of
1. Collect complete pressure loss: ULPA is only part of the system resistance
In addition to ULPA, it also includes pre-filtration, air ducts, inlets, outlets and internal losses of equipment, and unified definitions of flow and pressure.
The total resistance of the system is the sum of the resistances of each section. The initial resistance of ULPA is usually in the range of 180-280 Pa. The final resistance is recommended to be controlled at 2 times the initial pressure difference or no more than 600 Pa. However, the resistance of pre-filtration, air duct elbows, inlet grilles and internal structures of the equipment also need to be taken into account. If only the filter resistance is calculated, the fan selection will be too small; if all the resistance is calculated on the filter head, the filter demand will be overestimated. Aili Industry isThe HEPA/ULPA filter matching plan lists the resistance by system components.During the complete test of the FFU fan filter unit , the pressure drop of each section is recorded, and the working point calculation has complete itemized data. The relationship between levels and filtering requirements can be found inISO cleanliness level comparison。
2. Check the old and new resistance ranges: both the initial point and maintenance status should be checked
Check the clean filter element and the operating ability when reaching the project maintenance limit, and evaluate the speed range, power and noise, rather than just looking at a single initial point.
Filter resistance will increase with operating time. If the fan is only matched according to the initial resistance of the new filter element, the air volume will decrease in the middle and late stages of operation; if the fan is matched according to the final resistance but the margin is too large, the fan may operate in the low-efficiency zone during the new filter element stage. A reasonable approach is to check both the initial resistance and final resistance states on the fan curve to confirm that both operating points are within the acceptable range. Aili Industry isThe technical data of ULPA ultra-high efficiency filter gives both the initial resistance and the recommended final resistance.The FFU computer group control system can record the resistance change trend to facilitate comparison of actual operating performance in the two states. The relationship between filter resistance and operating status can be found inHEPA FAQs and Selection Guide。
3. Use a prototype to calibrate the curve: the measured working point is more reliable than the calculated one
After installation, measure the air volume and pressure difference to confirm the actual interface loss and distribution. When the deviation is large, the reason should be found instead of increasing the speed without limit.
The theoretical calculation gives the design operating point. In the actual system, the operating point may deviate due to the influence of the installation interface, sealing state and air flow distribution. Aili Industry isEFU equipment end fan filter unit andThe measured air volume and pressure difference during the complete test of the FFU fan filter unit are compared with the designed operating point; when deviations are found during the prototype stage, the reasons are found from the interface loss, sealing status and air flow distribution, rather than simply increasing the speed to make up for the air volume. The actual measured conditions of the equipment end working point can be referred toEFU FAQ and technical support。
4. When the rated air volume of the fan is satisfied but the available pressure is insufficient, the air volume will still decrease after installing ULPA.
When the rated air volume of the fan meets the requirements but the available pressure is insufficient, the air volume may still decrease after the ULPA is installed and needs to be rematched. The rated air volume is the maximum value under no-resistance or low-resistance conditions. In the actual system, filter resistance and air duct resistance will consume the available pressure of the fan, and the operating point moves along the performance curve toward the direction of small air volume.
Aili Industry isWhen selecting non-standard ULPA filter projects, check the available pressure of the fan based on the total system resistance at the target air volume, rather than just looking at the rated air volume;When selecting the FFU fan filter unit, the air volume-static pressure curve and filter resistance data are provided at the same time, and the working point can be read directly on the curve. For the judgment method of working point offset, please refer toFFU FAQ and technical support。
5. Related questions and answers
Can constant air volume control solve insufficient residual pressure?
The control can only be adjusted within the fan's capabilities and cannot maintain the target when capabilities are exceeded.
The rated air volume of the fan meets the requirements. Why is the air volume not enough after installation?
The rated air volume is the maximum value under no resistance. In the actual system, the filter resistance and air duct resistance will consume the available pressure, and the working point will shift towards the direction of small air volume.
Should the working point match the initial resistance or the final resistance?
It is recommended to check both states to confirm that the operating points under initial resistance and final resistance are within the acceptable range.
6. Related articles
ULPA ultra-high efficiency filter FAQ and selection guide
FFU computer group control system
7. Key points for selection and acceptance inspection
Check items |
Check the key points |
|---|---|
system resistance |
The losses of filters, pre-filtration, air ducts and interfaces are calculated in stages. |
resistance range |
Check both the initial resistance and final resistance states. |
fan curve |
Relationship between air volume and static pressure at target speed |
Actual measurement at working point |
Comparison of air volume and pressure difference with design values after installation |
Deviation handling |
Check the interface loss and sealing status, not just to speed up |
8. Product matching and technical support from Aili Industrial
Aili Industry also produces fans, filters and complete machines.FFU fan filter unit andthe fan filter unit at the EFU equipment end come from the same system, and the working point calculation is performed on the basis of complete data.The fan performance curve and filter resistance data of The HEPA/ULPA filter matching plan lists the resistance by system components.The technical data of ULPA ultra-high efficiency filter also gives the initial resistance and recommended final resistance;The FFU fan filter unit was tested to record the pressure drop in each section and measured the air volume pressure difference, and compared it with the designed operating point.The non-standard ULPA filter project checks the available pressure of the fan based on the total system resistance under the target air volume.The FFU computer group control system records the resistance change trend to facilitate comparison of the actual performance of the two states. 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.
