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Jason@cleanroomequips.com
Purpose
To specify the test conditions and methods for Wind speed, Air volume and Ventilation frequency of clean rooms (areas), standardize the test operation and ensure the accuracy of the test results.
Scope
Applicable to the test of wind speed, air volume and ventilation frequency of clean rooms (areas) of the company.
Responsible persons
Environmental monitor, QA, director of central laboratory, supervisor of quality assurance room.
Content
1. Test instruments
a. Anemometer
The minimum scale or reading should not be greater than 0.02m/s. It is used for Wind speed test of clean rooms with unidirectional flow and wind catch test of sleeve method and air outlet method.
b. air flow hood
It should be equipped with a flow meter to directly obtain the air volume. It is suitable for the test of wind speed, air volume and ventilation frequency of clean rooms with direct turbulent flow
2. Test conditions
When accepting the clean room, the air volume and wind speed test must be carried out first, and the effects of each item of purification air conditioning must be obtained under the designed air volume and wind speed conditions.
Before the Air volume test, it is necessary to check whether the fan is running normally, whether the components in the system are installed correctly, whether there are any obstacles, all valves should be fixed in a certain open position, and the size of the measured air outlet and air duct must be actually measured.
The test should be carried out after the air conditioning system has been running normally for no less than 30 minutes.
When any method is used to measure the air volume (wind speed) of any clean room, any accessories and decorations on the air outlet should remain the same.
3. Test method
a. For unidirectional clean rooms, the air supply volume can be determined by the method of cross-sectional average wind speed (V) and cross-sectional area product (S). The measurement section of the vertical unidirectional clean room is the horizontal section of the unobstructed surface (except orifice plate and grille) 0.8m from the ground. If there is a blocking surface, the measurement section should be raised to 0.25m above the blocking surface; the horizontal unidirectional clean room takes a section perpendicular to the ground 0.5m away from the air supply surface. The distance between the measuring points on the section should not be greater than 1m, generally 0.3m. The number of measuring points should be no less than 20 and evenly arranged.
b. For non-unidirectional clean rooms, the air outlets with filters installed inside can be measured by the sleeve method and the air volume setting method. The air outlet method can also be used to measure the air volume of the return air outlet or fresh air outlet.
①
A--One of the side lengths of the air duct opening
B--The length of the air duct opening
A straight pipe section with the same or similar cross-section as or similar to the air outlet and a length greater than 2 times the side length of the air outlet can be made of lightweight sheet material or membrane material as an auxiliary air duct, which is connected to the outside of the filter air outlet. On the plane of the sleeve outlet, small squares are evenly divided, and the side length of the square is not greater than 200mm. Measuring points are set in the center of the square, but the minimum number of measuring points is not less than 6 points. A conical sleeve can also be used, with the upper opening and the same or similar cross-section as the air outlet, the area of the lower opening is not less than half of the area of the upper opening, the length should be greater than 1.5 times the side length of the air outlet, and the inclination angle (α) between the side wall and the vertical plane should not be greater than 7.5°. The average wind speed of the cross section is measured, and the air volume is calculated by multiplying it by the net area of the measured cross-sectional surface.
②Air volume hood method
This method uses an air volume hood with a flow meter to measure wind speed and air volume. This method can directly obtain the air volume. The area of the air volume hood should be close to the area of the air outlet. When measuring, the air volume hood should completely cover the filter or air outlet, and the air volume grommet and the contact surface should be tight and leak-free.
③Air outlet method
When measuring negative pressure air volume such as fresh air volume and return air volume, if it is limited by environmental conditions and it is impossible to use a sleeve or air volume hood, and it is impossible to detect on the air duct, the air outlet method can be used. When there are accessories such as nets, perforated plates, and louvers on the air outlet, the measuring surface should be about 50mm away from it, and the measuring area is calculated according to the area of the air outlet, and the number of measuring points is as specified in 3.2.1. For louver air outlets, no less than 3 points can be selected between every two louvers, and the measuring points should be facing the oblique airflow between the blades. The measuring area should be calculated according to the net area of the airflow passing through the louver air outlet.
4. Calculation
a. Average wind speed (V)
Where V1, V2, .....n are the wind speeds of each measuring point, m/s; n is the total number of measuring points.
b. Air volume (L)
Where: L--air volume of each air outlet, m3/h;
S--ventilation area of the air outlet, m2:
V--measured average wind speed of the air outlet, m/s.
c. Room ventilation times (N):
times/h
Where: L1+L2+...Ln--air volume of each air outlet in the room (m3/h); A--room volume.
