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How to check whether the air velocity of the clean shed meets the standard?
How to check whether the air velocity of the clean shed meets the standard?To detect whether the airflow speed of the clean shed meets the standard, it can usually be detected by professional instruments, or judged by observing the airflow visualization. The following are the specific methods:Use an anemometer to detect Select the right anemometer: Select the right anemometer according to the airflow velocity range and accuracy requirements of the clean shed. Common anemometers are hot wire anemometer, impeller anemometer, pitot tube anemometer and so on. For the detection of air velocity in the clean shed, hot-wire anemometer is more commonly used, which has high accuracy, fast response speed, and can accurately measure low wind speed. Determine measuring points: according to the size and shape of the clean shed, determine the location and number of measuring points by relevant standards or specifications. Generally speaking, for unidirectional flow clean sheds, measuring points can be evenly arranged on the cross-section of the working area, and the spacing is usually 0.5-1 meters; For non-unidirectional flow clean sheds, measuring points can be set at key positions of the air supply outlet, return air outlet and working area. Measuring operation: Place the probe of the anemometer on the measuring point, keep the probe perpendicular to the direction of the airflow, and record the data after the anemometer reading is stable. Each measuring point should be measured at least 3 times, and the average value is taken as the airflow speed at that point. Data analysis: The data of all measuring points are sorted and analyzed, and compared with the air velocity standard required by the clean shed design. Check whether there are areas where the airflow speed is too high or too low and whether the uniformity of the overall airflow speed meets the requirements. Detection by smoke generator Prepare the smoke generator: Choose a smoke generator suitable for use in a clean environment, and the smoke generated by it should have good visibility and stability, and will not pollute the environment and equipment in the clean shed. Operate the smoke generator: Start the smoke generator at different positions in the clean shed to release the smoke. Observe the flow status and direction of the smoke to determine whether the airflow is uniform and whether there are vortices or areas of stagnant air flow. Assessment of airflow conditions: According to the flow of smoke, the airflow organization and speed of the clean shed are qualitatively assessed. If the smoke can flow evenly and smoothly and discharge the clean shed within the specified time, it indicates that the air velocity and air organization meet the requirements; If the smoke is found to accumulate or flow abnormally, there may be uneven airflow speed or local airflow problems, which need to be further detected and analyzed. Other detection methods Tracer gas method: A certain amount of tracer gas, such as sulfur hexafluoride, is released in the clean shed, and then by detecting the concentration distribution and attenuation of the tracer gas, the flow speed and the number of air changes are calculated, to assess whether the flow condition of the clean shed meets the standard. Laser particle counter assisted detection: Laser particle counter is mainly used to detect the concentration of particulate matter in the air, but to a certain extent, it can also reflect the airflow speed. When the airflow speed is normal, the particles can be effectively taken away, and the particle concentration detected by the particle counter should be within the normal range. If the concentration of particles detected by the particle counter in a certain area is abnormally high, it may indicate that the airflow speed in the area is too low to discharge the particles in time. |
