If the FFU filter element passes the leak test, why should we check the installation seal?

If the filter element passes the leak test, it does not mean that the seal is intact after installation.

The HEPA or ULPA filters used by FFU are usually leak tested before leaving the factory. Qualified leak detection means that the filter itself does not exceed the allowable leakage under the test conditions. This is an important guarantee of filter quality.

However, if the filter passes the factory leak test, it only shows the integrity of the filter product itself. After the filter is installed in the FFU box, it will also go through multiple links such as frame sealing, compression mechanism, and box interface. If the installation seal is not in place, unfiltered air may bypass the filter and enter the clean area, causing leaks. This leakage has nothing to do with the filter itself, but can still affect cleanliness.

Therefore, filter leak detection and installation seal inspection are two different links and cannot replace each other. If the filter leak test is qualified, the installation seal still needs to be confirmed separately. Aili Industry has complete production capabilities in FFU complete machines and filter matching, and can cooperate with the project to confirm the installation and sealing. For the basic structure of the FFU machine, please refer toAili Industrial FFU fan filter unit。

What does a filter leak check check for?

Filter leak detection usually uses the scanning method, which scans the filter outlet surface along a certain path to detect whether there is particle leakage exceeding the allowable value. The leak detection object is the filter body, including filter material, frame and sealant. A filter that passes the leak test means that its body has no obvious leakage under the test conditions.

The conditions for filter leak detection include test air volume, test particle size, scanning speed and judgment standards. Different standards have different requirements for leak detection. Filter leak detection records usually correspond to the filter batch or number.

Filter leak detection does not involve the FFU box, installation frame and sealing strip. The status of these areas requires additional inspection.

What to check when installing seal

The objects of the installation seal inspection are the sealing interface between the filter and the FFU box, as well as the connection between the box and the installation frame. The inspection contents include: whether the sealing strip is installed in place, whether the pressing mechanism is pressed evenly, whether the sealing surface is clean and free of damage, whether the sealing liquid level of the liquid tank is normal, and whether the box joints are sealed.

Installation seal inspection is usually also performed when the FFU is running. Scan near the sealing strip to detect particle leakage. You can also use the smoke method to observe the direction of airflow. The results of the installation seal inspection and the filter leak detection results should be recorded separately.

Possible leak paths after installation

After the filter is installed, there are several possible leak paths. There is insufficient compression between the sealing strip and the filter frame, forming a gap. The contact between the sealing strip and the sealing surface of the box is poor, forming a bypass. The pressing mechanism is uneven and some sealing strips are not pressed tightly. The sealing strip is aged, deformed or damaged. The liquid tank sealing liquid level is insufficient or the knife edge is not inserted deep enough. Box seams, cable penetrations, or access doors are not sealed.

These leak paths may not all be exposed on the day of installation. Some may appear due to vibration, temperature changes or sealing strip aging after running for a period of time. Therefore, installation seal inspection must not only be performed after installation, but also be confirmed regularly during operation and maintenance.

Installation seal inspection method

The installation seal inspection method is similar to the filter leak inspection, but the focus is on the sealing interface. Commonly used methods include particle counting scanning, smoke generation, and pressure decay methods.

The particle counting scanning method slowly moves the probe near the sealing strip to detect changes in particle concentration. If the particle count is significantly elevated somewhere, there may be a leak. The smoke method releases smoke near the sealing strip and observes whether the smoke is inhaled or blown out. The pressure decay method can confirm the overall sealing status.

The inspection location, method, instrument and results should be recorded during inspection. If a leak is found, the location should be marked, dealt with and retested.

What should leak detection records include?

A complete leak detection record should include the following: filter number or batch; filter factory leak detection results; installation seal inspection methods and results; inspection locations and measuring points; FFU operating status at the time of inspection; inspection instruments and calibration status; inspection personnel and dates; problems found and handling measures; retest results.

These records can support subsequent maintenance and troubleshooting. If a certain FFU has a cleanliness problem during operation, the leak detection record can help determine whether it is a filter problem or an installation seal problem.

Issues that should be confirmed in advance during project communication

During the FFU leak detection and acceptance stage, it is recommended to confirm the following with the manufacturer: filter factory leak detection methods and standards; installation seal inspection methods and judgment standards; operating status and air volume during leak detection; leak detection instruments and calibration requirements; leak detection record format; processing procedures for leak detection; whether the manufacturer is required to be on site to support leak detection; and leak detection cycles during operation and maintenance.

If you are doing FFU leak detection and acceptance, you can visitAili Industrial FFU fan filter unit to learn about the complete machine configuration, you can also refer toFFU is equipped with ULPA ultra-high efficiency filter to learn about the filter and installation interface, or contact Aili Industrial for leak detection support.

in conclusion

If the filter passes the factory leak test, it only indicates the integrity of the filter body. The installation seal still needs to be inspected separately. After installation, there may be leakage paths such as frames, gaskets, pressing mechanisms, liquid tanks, and box interfaces. Filter leak detection and installation seal inspection should be carried out separately and complete records should be kept.

Aili Industrial has complete production capabilities in FFU complete machines and filter accessories, and can cooperate with the project to confirm installation sealing and leak detection. If you need to know more about FFU leak detection methods, you can visitAili Industrial FFU fan filter unit , you are also welcome to contact Aili Industrial for project support.