Purpose and method of detecting airflow flow pattern in clean room

2019-05-29 14:50:00   Editor: Yan Hong shares    0

The purpose of the clean room airflow pattern is to clarify the influence of equipment or facilities in the clean room on the airflow, select or improve the airflow pattern to minimize turbulence (eddy current), and increase the maximum self-purification or recovery rate of the clean room. Shorten the self-cleaning time.

Detection method of airflow pattern in clean room: measuring point arrangement. Test according to the HVAC System Air Flow Pattern Test Procedure. The specific steps are as follows:

(1) Vertical unidirectional flow (laminar flow) clean room select one vertical and horizontal cross section, and one horizontal plane with height of 0.8m and 1.5m from the ground; horizontal unidirectional flow (laminar flow) clean room chooses longitudinal section and There is one horizontal plane at the height of the working area, and three cross sections from the returning wind wall 0.5m and the center of the room. The spacing between the measuring points on all sides is 0.2~1m.

(2) The turbulent flow clean room is selected by the longitudinal and cross sections of the center of the representative air supply port and the horizontal plane of the working area. The distance between the measuring points on the section is 0.2~0.5m, and the spacing between the measuring points on the horizontal plane is 0.5~1m. There should be a measuring point on the middle line between the two tuyères.

(3) The test shall be carried out after the air purification control system or the laminar flow purification device is operating normally and the airflow is stabilized. According to the "Wind Speed Test Procedure", the wind speed of the air supply or laminar flow purification device is checked to meet the specified requirements. Check the differential pressure gauge reading to confirm that the clean room pressure differential meets the specified requirements.

(4) Use the airflow type test smoke generating device (Shanghai Net Purified Smoke Generator Y09-010) to release visible at the specified measuring point and "typical position" (the product or raw material exposed above and around the working environment, etc.) Smoke and a visible streamline with the airflow. Use a cigarette lighter or a hanging monofilament thread to observe and record the airflow pattern (if possible, if possible), and mark the flow direction on the cross-section of the measuring point arrangement.

(5) Shoot the down stream when the smoke flows through the “typical position”. Smoke should be able to flow through these “typical locations” without backflow due to turbulence of the air. Otherwise, the air purification adjustment system, air shower room position or material placement position should be adjusted.

(6) Take down the streamline when the operator enters the laminar flow protection zone for operation. Smoke should not return to any point in the “typical position” during operation, otherwise procedures or measures to prevent contamination must be established.

(7) Verify that the resulting turbulence will carry contaminants from other locations to the critical operating point of the pipeline. If possible, adjust the airflow for minimal turbulence and clean quickly. If turbulence cannot be prevented, different aerodynamic models must be established (eg using a diffuser on the filling equipment).

Acceptable criteria: the flow pattern should be drawn and the flow diagram should be analyzed and interpreted.

Instruments to be used in the test: airflow type test smoking device