SOP For Airflow Velocity and Uniformity Test

PURPOSE:

The purpose of the SOP for this test is to evaluate airflow velocity and uniformity of airflow velocity in cleanrooms and clean zones.

APPARATUS:

Refer Annex I (Table 1: Minimum Instrumentation requirements)

TEST CONDITIONS AND PROCEDURE:

General considerations:

1. Measurement of airflow velocity is applicable in unidirectional airflow cleanrooms or clean zones and is optional in non-unidirectional installations when the purpose of measurement is to evaluate its uniformity.
2. Measurement of supply airflow volume is also performed to evaluate the arithmetic air exchange rate in the installation.
3. For air flow velocity measurements, define the measuring plane perpendicular to the supply air flow and divide the measuring plane into grid cells of equal area.
4. The number of measuring points should be more than the square root of 10 times the measuring plane area in square meters and should be not less than 4 points.
5. Measurements should be taken at the center of each grid cell.
6. The location of the airflow reading in the work zone shall be as specified in the contract documents or as agreed between the customer and supplier.
7. For filter face air flow velocity, the tests are performed at a distance of between 150mm to 300 mm from filter face.
8. For room airflow velocity, the tests are normally performed at a specific work surface elevation (Normally 0.91 m (36”) above the floor).
9. If applicable, and as agreed between the customer and supplier, the variance and standard deviation may be added to the test record.

PROCEDURES:

A: Filter face airflow velocity: Unidirectional

1. The measurement area shall be cross sectional area of the filter face normal to the airflow. This area shall consist of the net effective filter media area, which is exclusive of the filter frame or patch area of filter.
2. When using single point measurement instrument, such as hot wire anemometer, divide the net filter face into grids of equal area of not greater than 0.09 square meters (1.0 square foot).
3. When using multi-point instrument, divide the net filter face into grids of equal area of not greater than 0.37 square meters (4.0 square feet).
4. Special care is necessary to keep the sampled area unobstructed during the air flow measurement. The use of a support stand is recommended with single point type measuring instruments.
5. Take the measurements for a minimum 5 seconds or as per instrument manufacturer’s guidelines.

ACCEPTANCE:

1. The average airflow velocity for the filter should be within +/- 10 % of that specified in the contract documents or as agreed between the customer and the supplier.
2. The standard deviation (if required) should not exceed 15 % unless otherwise specified in the contract documents or as agreed between the customer and the supplier.

REPORTING:

By agreement between the customer and the supplier, the following information and data should be recorded:

1. Identification of apparatus or data collection system
2. Identification of apparatus and calibration status
3. Type of tests and measurements, and measuring conditions
4. Measurement locations
5. Temperature, humidity and environmental data
6. Occupancy state (s).

B: Filter face airflow velocity: Non – Unidirectional (Volume method)

1. The measurement area shall be cross sectional area of the filter face normal to the airflow. This area shall consist of the net effective filter media area, which is exclusive of the filter frame or patch area of filter.
2. When using single point measurement instrument, such as hot wire anemometer, divide the net filter face into grids of equal area of not greater than 0.09 square meters (1.0 square foot).
3. When using multi-point instrument, divide the net filter face into grids of equal area of not greater than 0.37 square meters (4.0 square feet).
4. Special care is necessary to keep the sampled area unobstructed during the air flow measurement. The use of a support stand is recommended with single point type measuring instruments.
5. Take the measurements for a minimum 5 seconds or as per instrument manufacturer’s guidelines.

ACCEPTANCE:

1. Measure the total airflow for each filter. Determine the average filter face velocity by dividing the measured airflow by the net effective filter area.

V_s = Q_s/A_s

V_s = Supply airflow velocity at each filter

Q_s = Supply airflow volume from each filter

A_s = Net Effective filter area

2. The average airflow velocity for the filter should be within +/- 10 % of that specified in the contract documents or as agreed between the customer and the supplier.
3. The standard deviation (if required) should not exceed 15 % unless otherwise specified in the contract documents or as agreed between the customer and the supplier.

REPORTING:

By agreement between the customer and the supplier, the following information and data should be recorded:

1. Identification of apparatus or data collection system
2. Identification of apparatus and calibration status
3. Type of tests and measurements, and measuring conditions
4. Measurement locations
5. Temperature, humidity and environmental data
6. Occupancy state (s).

C: Filter face airflow velocity: Non – Unidirectional (Velocity method)

It is advisable to use the volumetric method (as described in point B) to calculate the filter face velocity in a non – unidirectional cleanroom, however when the project specifications require a direct velocity measurement, then refer to procedures and other details mentioned in point ‘A’ (Filter face airflow velocity)

D: Average room airflow velocity

1. For room airflow velocity, the tests are normally performed at a specified work surface elevation.
2. Measurement readings shall be taken at specified planes and locations in the room as specified in the contract documents or as agreed to between the customer and the supplier.

3. The measurement area shall be a cross-sectional area of the room or work area normal to the airflow. This area shall consist of the total work zone or room.
4. Divide the area plane at the measurement point into grids of equal area of not greater than 1.48 square meters (16 square feet), or as specified in the contract documents.
5. Special care is necessary to keep the sampled area unobstructed during the air flow measurement. The use of a support stand is recommended with single point type measuring instruments.
6. Take the measurements for a minimum 5 seconds or as per instrument manufacturer’s guidelines.

ACCEPTANCE:

1. The average airflow velocity for the cleanroom should be within +/- 10 % of that specified in the contract documents or as agreed between the customer and the supplier.
2. The average or total airflow volume for the cleanroom should be within +/- 10 % of that specified in the contract documents or as agreed between the customer and the supplier.
3. The standard deviation (if required) should not exceed 15 % unless otherwise specified in the contract documents or as agreed between the customer and the supplier.

REPORTING:

By agreement between the customer and the supplier, the following information and data should be recorded:

1. Identification of apparatus or data collection system
2. Identification of apparatus and calibration status
3. Type of tests and measurements, and measuring conditions
4. Measurement locations
5. Temperature, humidity and environmental data
6. Occupancy state (s).