How to choose FFU filter? How to match filter pressure difference with air volume?
Direct answer: First determine the filtration efficiency according to the cleanliness target and particle control requirements, then compare the filter pressure difference according to the FFU's design air volume, and check whether the fan can maintain the target air supply after the filter resistance increases. Dimensions, sealing structures, testing requirements and replacement conditions should also be confirmed at the same time. When the filtration level changes, you cannot just replace the filter material without reviewing the performance of the FFU machine.
The FFU filter is responsible for intercepting particles and also creates air resistance. If the filter is not selected appropriately, the efficiency may meet the requirements but the actual air volume is insufficient. Therefore, clean room or equipment-side projects should includeHEPA/ULPA air filters andThe FFU fan filter unit is selected as a set of equipment.
Step 1: Determine filtration efficiency according to process requirements
First clarify the cleanliness goals of the application area, the particles that need to be controlled, and the filter testing requirements agreed upon by the project, and then select the corresponding HEPA or ULPA solution. The decision cannot be made solely on the basis of 'the higher the filtration level, the better'; higher efficiency requirements may be accompanied by different resistance, structure and maintenance conditions.
For local equipment-side projects with high cleanliness requirements, the installation location of the filter, the air supply direction, and the available space inside the equipment should also be confirmed to avoid being unable to complete installation or maintenance even though the filter specifications meet the requirements.
Step 2: Compare the pressure difference under the design air volume
The filter pressure difference will change with the air volume passing through the filter material. When comparing different filters, suppliers should be asked to indicate the test air volume, filter specifications and test conditions , and try to use data that is close to the project's design air volume. By only comparing the single 'initial pressure difference' figure on the product data, it is impossible to judge its actual performance after being loaded into the FFU.
At the same time, it is necessary to distinguish the pressure difference between the filter itself and other system resistance after the FFU is installed. The air inlet and outlet structure of the equipment, the box and the on-site air flow path may also affect the working point, and these conditions should be included in the whole machine calibration.
Step 3: Check the air volume of FFU after the resistance changes
The initial differential pressure of a new filter is only a starting point for selection. After the resistance changes during operation, the air volume of the fixed-speed FFU may decrease; the FFU that maintains the air volume through speed regulation may change the operating gear and power consumption. Therefore, it is necessary to check the fan performance under the target air volume and clarify the filter resistance range and maintenance conditions allowed by the project.
If you plan to switch toFor ULPA filters , the fan operating point, complete machine air volume and energy consumption should be reviewed simultaneously. Just because the filter efficiency reaches the standard does not mean that the air supply performance of the FFU automatically reaches the standard after installation.
Step 4: Confirm size, sealing and replacement methods
The overall dimensions, frame structure and sealing method of the filter should match the FFU box. The technical agreement should also clarify the testing requirements for filters and complete machines, on-site maintenance directions and replacement space. For batch projects, a prototype can be used to confirm installation, sealing, air volume and pressure difference before finalizing the configuration.
Aili Industrial can match fans, motors, filters, boxes and control solutions based on the clean room ceiling module or equipment end installation conditions. After the project provides cleanliness requirements, target air volume, filter specifications, installation drawings and estimated quantities, it is easier to check the performance of the complete machine under agreed working conditions. The specific configuration and test results are subject to the project technical agreement.
Q: The lower the initial pressure difference of the filter, the more suitable the FFU is?
Answer: Not necessarily. It is also necessary to meet the filtration efficiency, sealing and testing requirements at the same time, and compare the pressure difference under the same design air volume.
Q: After replacing the ULPA filter, can the original FFU continue to be used?
Answer: The filter resistance, the fan operating point at the target air volume, as well as the installation size and sealing method should be rechecked. You cannot judge based on the same appearance.
Q: What information should be provided before purchasing?
Answer: It is recommended to provide cleanliness targets, particle control requirements, target air volume, installation dimensions, filter testing requirements and maintenance space, and agree on the test conditions for the entire machine.
