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Requirements for testing clean benches and the steps involved
Requirements for testing clean benches and the steps involvedI. Wind speed1) Divide the area of the 10cm plane downstream of the main filter or diffuser into no less than twelve equal areas, with the center of each area being the wind speed measurement point. However, the distance between the measuring points should not be greater than 25cm 2) Calculate the arithmetic mean of the cross-sectional air velocity and air velocity uniformity by calculating the air velocity value at each measurement point. II. Number of suspended particles (1) The concentration in the inhalation zone (≥ 0.5um particles) shall not be less than 35,000 particles / L; it cannot meet the requirements of the production of polydisperse aerosols in the inhalation zone; (2) In the center of a parallel section 250mm from the main filter or rectifier grille outlet for five consecutive tests, to find the average, the sampling volume should be not less than 1L. III. Precipitating bacteria Place a 90mm Petri dish containing nutrient agar on the operating interface of the bench and arrange the measurement points according to the suspended particles. After 0.5 hours of exposure, cover and remove the Petri dish and incubate at 30°C ~ 35°C for 48 hours. Visible bacterial colonies were counted with the naked eye and the arithmetic mean was taken. IV. illumination The measurement points are arranged on the horizontal center line of the clean bench, evenly distributed in three points, and the arithmetic mean is taken as the illuminance of the clean bench. V. High-efficiency filter (PAO) leak detection Aerosols are sent to the upstream side of the high-efficiency filter, while the aerosol generator is used to scan and check the downstream side approximately 2.5cm from the high-efficiency filter outlet. A significant leak is considered when the ratio of the concentration on the downstream side to the concentration on the upstream side is greater than 0.01%. VI. Noise Noise measurement points for clean benches should be arranged in the center of the bench, 20cm from the front edge of the bench, and at a height of 110cm (equivalent to the operator's sitting ear position). The noise measurement point for other localized clean equipment should be 100cm horizontal distance from the geometric center of the main surface of the equipment and 150cm high. it is recommended that one measurement is taken on each side and that the arithmetic mean of the four points is taken. VII. Airflow methods 1) Vertical airflow test The smoke is located 150mm inside the front window and moves at a height of 300mm from one side wall panel to the other side wall panel operating area. The vertical downward airflow from the clean bench is in a downward mode below the manifold and there is no upward airflow. The smoke is located at 1/2 the depth of the internal operating area of the front window and moves at a height of 300mm from one side wall panel to the other side wall panel operating area. The vertical downward flow from the clean bench is in a downward mode below the manifold. Upward airflow. The smoke is 150mm from the rear sidewall of the operating area and moves from one sidewall to the other in the operating area at a height of 300mm. The vertical downward airflow from the cleaning table is in a downward pattern at the lower part of the manifold and there is no upward airflow. 2) Horizontal airflow test The smoke is located at a depth of 1/2 of the internal operating area of the front window and moves from one sidewall panel to the other sidewall panel operating area at a height of 300mm. Horizontal airflow from the cleaning bench is in an outward mode in front of the diffuser hole. There is no inward airflow. |
