Calculation Formula for the Quantity Requirement of FFU in Class 1000 Cleanrooms
2024.12.16
In the construction and operation of cleanrooms, the proper configuration of FFU (Fan Filter Unit) is of crucial importance. It directly determines whether the cleanroom can achieve the expected cleanliness level, such as that of a Class 1000 cleanroom. Guangzhou Cleanroom Construction Co., Ltd. will introduce in detail the calculation formula for the quantity requirement of FFU in Class 1000 cleanrooms in this article, helping you better plan and design the ventilation and purification systems of cleanrooms.
I. Standard Parameters of Class 1000 Cleanrooms
A Class 1000 cleanroom means that the number of dust particles with a particle size greater than or equal to 0.5 micrometers should not exceed 1,000 per cubic foot (35.2 per cubic meter). Meanwhile, there are also strict requirements for parameters such as temperature, humidity, air change rate, and pressure difference. Before calculating the quantity of FFU, we need to clarify these key parameters first to ensure accurate subsequent calculations. Generally speaking, the temperature in a Class 1000 cleanroom is usually controlled at 22 ± 2 °C, the relative humidity is at 50 ± 5%, the air change rate is approximately 50 - 60 times per hour, and a positive pressure difference of 10 - 15 pascals is maintained with adjacent non-clean areas.
II. Key Factors in Calculating the Quantity of FFU
1. Room Area and Height: These are the most fundamental factors. The area of the room determines the spatial range that needs to be covered, while the height affects the circulation and distribution of air. Larger areas and higher spaces require more FFUs to ensure that the air can be fully circulated and filtered to meet the requirements of Class 1000 cleanliness. For example, compared with a cleanroom with an area of 50 square meters and a height of 2.5 meters, a cleanroom with an area of 100 square meters and a height of 3 meters will obviously need more FFUs.
2. Cleanliness Level Requirement: Class 1000 cleanrooms have strict limitations on the number of dust particles. This requires that FFUs can provide sufficient filtration efficiency and air circulation volume. The filtration efficiency of FFUs usually needs to reach 99.99% or above, with a high filtration capacity for particulate matter of 0.3 micrometers and above, to ensure that the air quality in the cleanroom meets the Class 1000 standard.
3. Air Change Rate: As mentioned above, the air change rate of Class 1000 cleanrooms is generally 50 - 60 times per hour. The higher the air change rate, the higher the frequency at which the indoor air is replaced in a unit time, which requires more FFUs to drive air circulation and filtration. A higher air change rate helps maintain the stability of indoor cleanliness, but it will also increase energy consumption and equipment costs. Therefore, it is necessary to reasonably determine the air change rate and the quantity of FFUs while meeting the cleanliness requirements.
III. Calculation Formula for the Quantity of FFU
1. Principle of Formula Derivation: The calculation of the quantity of FFUs is based on the volume of the cleanroom, the air change rate, and the supply air volume of a single FFU. First, we calculate the volume of the cleanroom through the length, width, and height of the room (V = L × W × H, where L is the length, W is the width, and H is the height). Then, according to the required air change rate (N), we obtain the total supply air volume required in a unit time (Q = V × N). Finally, we divide the total supply air volume by the rated supply air volume (q) of a single FFU to get the approximate quantity of FFUs (n = Q / q).
2. Example of Practical Application: Suppose we have a Class 1000 cleanroom with a length of 20 meters, a width of 10 meters, and a height of 2.8 meters. The rated supply air volume of the selected FFU is 1,000 m³/h, and the air change rate is calculated as 55 times per hour. First, calculate the volume of the cleanroom: V = 20 × 10 × 2.8 = 560 m³. Then calculate the total supply air volume: Q = 560 × 55 = 30,800 m³/h. Finally, calculate the quantity of FFUs: n = 30,800 ÷ 1,000 = 30.8. Since the quantity of FFUs must be an integer, it is rounded up to 31 units.
IV. Precautions
1. Layout Rationality: When determining the quantity and positions of FFUs, the internal layout of the cleanroom should be considered to avoid the occurrence of dead air zones or short-circuiting of airflows. FFUs should be evenly distributed on the ceiling of the cleanroom to ensure that the air in the entire space can be circulated and filtered evenly. Meanwhile, the layout of FFUs should be reasonably adjusted according to factors such as equipment placement and personnel operation areas to meet the high cleanliness requirements of local areas.
2. Margin Consideration: When actually calculating the quantity of FFUs, it is recommended to appropriately increase a certain margin, generally 10 - 20%. This is because during the actual operation process, situations such as filter blockage and a decline in fan efficiency may occur, resulting in a reduction in the supply air volume. Reserving a certain margin can ensure that the cleanroom can still maintain a stable cleanliness level during long-term operation, and also provide a certain degree of flexibility for possible future process adjustments or equipment upgrades.
3. Maintenance and Servicing: After determining the quantity of FFUs, attention should also be paid to their subsequent maintenance and servicing work. Regular replacement of filters, inspection of the operating status of fans, cleaning of the surfaces of FFUs and other maintenance measures can ensure that FFUs always maintain good performance, extend their service life, and reduce operating costs. Meanwhile, a reasonable maintenance plan also helps to ensure the stability of the cleanliness of the cleanroom and reduce the risk of production interruption caused by equipment failures.
Through the detailed introduction of the calculation formula for the quantity requirement of FFU in Class 1000 cleanrooms above, we believe that you have a deeper understanding of the design of the ventilation and purification systems of cleanrooms. Guangzhou Cleanroom Construction Co., Ltd. has a professional technical team and rich experience in cleanroom construction, and can provide you with one-stop solutions from design, construction to maintenance. If you encounter any problems during the construction of cleanrooms, please feel free to contact us. We will serve you wholeheartedly.
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