To confirm how many FFUs are needed in a cleanroom, you can make a comprehensive evaluation and calculation based on the air-exchange or the air velocity, which has corresponding recommended values for the number of air-exchanges and the average air velocity needed for different levels of cleanrooms in ISO14644-1. The number of air changes method is to calculate the total air volume through the whole room and the recommended number of air changes, so as to get the number of FFU required. Air velocity method is to compare the required air velocity of the cleanroom (the recommended value in ISO14644-1) and the air velocity of the FFU, which will lead to the number of FFU required according to the room area and the FFU air supply area.
The airflow and applicable area of FFU depends on the specification or model of FFU. For example, the air volume of conventional 2*4 FFU is about 1000 CMH, and different models of FFU correspond to different air volume (please refer to the specification table for details.) The applicable area of FFU is also different according to the height of the cleanroom and the clean level, and it is necessary to calculate the air volume required for the unit area of the cleanroom according to the cleanroom cleanliness. Then the applicable area of the different models of FFU can be calculated.
FFU has its own fan and high-efficiency filter, and the air supply is even and stable. Generally speaking, when FFU surface air velocity uniformity is tested, 6-12 points should be selected at the surface, and the maximum and minimum air velocity compared to the average value shall not exceed plus or minus 20%. In this case, FFU is considered to provide stable and uniform air to the clean area. The coverage of FFU mainly depends on its size and arrangement. For the higher cleanliness requirements area (ISO 5 and above), full coverage of FFUs are necessary to form laminar flow.
The general air velocity of FFU’s air supply surface is 0.45m/s±20%. Airkey has designed special FFUs with higher air velocity and larger air volume according to the customer's demand, and the air velocity can reach up to 1.5-2.0m/s; the cleanliness monitoring of the clean area can be done by using the real-time monitoring system of cleanliness, which can monitoe the cleanliness in the pee-determined test points. In addition, regular inspection and evaluation of the clean room and manual testing of cleanliness should be conducted in critical areas.
The service life of FFU motor can usually reach 100,000 hours, but the specific service life will also be affected by environmental factors.
FFU maintenance measures are mainly:
1. Regular inspection and replacement of filters (recommended to clean pre-filters once a month, replace HEPA filters once a year).
2. Regular inspection of the electrical wiring of the FFU and terminals to ensure that there is no loosening, aging or damage.
3. Regular FFU performance test to find if there is any FFU performance decline or failure, and take appropriate measures. Main replacement parts for FFU include motor and HEPA filters, and the replacement cost depends on the use of the motor and filter brand, model specifications and other parameters.
The effect of HEPA filter will be gradually reduced with the service time, and it is necessary to periodically determine whether it needs to be replaced. The general replacement cycle of HEPA filters is about one year, and more accurate judgment can also be made by observing the appearance and testing the performance. First of all, observe the appearance of the filter, to check whether there is damage, deformation, obvious dirty blockage and other phenomena. If there is, it is time to consider replacing the filter. In addition. It is also feasible to test the HEPA filter resistance. When the HEPA filter resistance reaches twice the initial resistance, it needs to be replaced. If the FFU is equipped with a pre-filter, the pre-filter needs to be cleaned/replaced once a month.
Customized FFU solution generally includes:
1. Understand the customization needs and site conditions
2. Design customized solutions
3. Production, installation and commissioning
4. After-sales maintenance of equipment.
FFU is usually installed on the ceiling of clean area to provide uniform and stable clean air for the whole clean area. FFU can also be installed on the equipment or above/side of the important working position as required to improve the cleanliness of the partial environment. With modular design, flexible and easy to replace, install and move, etc., FFU can be installed and used in the designated location as long as the installation space is sufficient.
FFU and speed controller can be separated and installed in different locations, so that it is more convenient for workers to switch on and off the FFU, regulate the air speed, etc. FFU and speed controller are connected by power/signal lines to ensure the normal operation of FFU.
FFU supports intelligent control and monitoring. It can be connected with the communication line to central computer to realize intelligent control and group control function. The group control function can realize centralized or partitioned control of multiple FFUs in the area: one-key switching, centralized/single speed control, real-time monitoring, FFU failure alarm, high efficiency filter clogging alarm and other functions.
