Clean Room Quiz 6
Question: What is the purpose of an airflow direction test and visualization?
Answer: The purpose of an airflow direction test and visualization is to demonstrate that the airflow direction and its uniformity of velocity conform to the design and performance specifications.
Question:
What are the four methods used for performing the airflow direction test and visualization?
Answer:
The four methods used for performing the airflow direction test and visualization are as follows:
- a) Tracer thread method;
- b) Tracer injection method;
- c) Airflow visualization method by image processing techniques;
- d) Airflow visualization method by the measurement of velocity distribution.
Additional Explanation:
a) and b) methods involve visualizing airflow using fibre tracer thread or tracer particles, recorded by devices like video cameras. These methods require careful selection of materials to avoid contamination and ensure accurate airflow profiling. Additional equipment such as tracer particle generators and high-intensity light sources may be employed.
Method c) utilizes image processing techniques to quantitatively demonstrate airflow velocity distributions within the cleanroom or clean zone.
It’s crucial to prevent interference with airflow patterns during testing to ensure accurate results.
Question:
What are the factors that affect airflow, and what is the significance of appropriate airflow visualization techniques?
Answer:
The factors affecting airflow include air pressure difference, air velocity, and temperature. Appropriate airflow visualization techniques are crucial for assessing the effectiveness of air distribution in unidirectional airflow cleanrooms, clean zones, and controlled zones. Additionally, these techniques can also be applied in non-unidirectional areas to evaluate airflow performance.
Question:
How is the tracer thread method conducted, and what is its purpose?
Answer:
The tracer thread method involves observing tufts such as silk threads, single nylon fibers, or thin film tapes placed on support sticks or wire grids within the airflow. These tufts serve to visually indicate the direction of airflow and any fluctuations caused by turbulence. Effective lighting enhances the observation and recording of airflow patterns.
Question:
What is the tracer injection method, and how is it conducted?
Answer:
The tracer injection method involves observing or imaging the behavior of tracer particles, illuminated by high-intensity light sources, to assess airflow direction and velocity uniformity in cleanrooms, clean zones, or controlled zones. Tracer particles, generated from materials like de-ionized water, sprayed alcohol/glycol, etc., are carefully selected to prevent surface contamination. Consideration of droplet size is important to ensure detectability without diverging from the observed airflow.
Question:
What is the airflow visualization method by image processing techniques, and how is it implemented?
Answer:
The airflow visualization method by image processing techniques involves processing particle image data obtained from video frames or films to obtain quantitative characteristics of airflow, typically represented by two-dimensional air velocity vectors within the area. Implementation of this method requires a digital computer equipped with suitable interfaces and specialized software for image processing. For enhanced spatial resolution, additional devices like laser light sources can be utilized.
Question:
How can airflow distribution be evaluated, and what equipment is used for this purpose?
Answer:
Airflow distribution can be evaluated by measuring velocity distributions using air velocity measuring apparatus such as thermal or ultrasonic anemometers. These instruments are placed at several defined points within the cleanroom or clean zone under investigation. Processing the measured data provides information about the airflow distribution within the area.
Question: What are the materials or particles used in tracer thread or injection methods.
Answer: Following materials or particles used in tracer thread or injection methods as given below table
| Item | Description |
| Material used in the tracer thread method | Silk thread, cloth, etc. |
| Particulate method used in the tracer injection method | DI water or other fluid mist of 0.5 μm to 50 μm in diameter. Bubbles of neutral density in the air at the measuring location. Organic or inorganic test fog. |
| Image recording devices for recording the visualized pictures or images of tracer particles | Various devices, such as photographic cameras, video cameras, including high-speed or strobe or synchronized functions and image recording devices, used in flow visualization procedures. |
| Various illumination light sources for contrasted observation or imaging of airflows | Tungsten lamp, fluorescent lamp, halogen lamp, mercury lamp, laser light sources (He-Ne, argon ion, YAG lasers, etc.) with or without stroboscope or synchronized devices to the recorders. |
| Image-processing technique for quantitative measurement by flow visualization | Laser light sheet method, consisting of high-power laser sources (argon or YAG laser), optics including cylindrical lens, and a controller, where two-dimensional airflows are visualized. |
Question:
What information and data should be recorded in test reports of airflow visualization, according to the agreement between the customer and supplier?
Answer:
According to the agreement between the customer and supplier, the following information and data should be recorded in test reports of airflow visualization:
- a) Type of tests, method of visualization, and test conditions.
- b) Type designations of each measuring apparatus used and its calibration status.
- c) Visualization point locations.
- d) Images stored on photographs or any other recording media, or raw data for each measurement, in the case of the image processing technique or the measurement of velocity distributions, if specified.
- e) A plan detailing the exact location of all apparatus accompanying the flow visualization report.
- f) Occupancy state(s).
