Performance verification of vacuum freeze dryer

● Drying oven shelf cooling rate test

● Uniformity test of shelf temperature

● In situ sterilization test

● Noise test

Vacuum leakage rate test of freeze-drying machine

● Water vapor trap water capture capacity test

Introduction to Testing Methods

1. Cooling rate test of drying oven shelf

Connect the water valve, turn on the power switch, and start timing when the shelf temperature is adjusted to 20 ℃. When it drops to -50 ℃, check the time taken for this process.

2. Uniformity test of shelf temperature

Place five temperature sensors with flat contact surfaces and an accuracy of ± 0.1 ℃ at any position on each shelf, close the door of the drying oven, start the machine to heat up to 50 ℃, keep it warm for 30 minutes, observe the temperature displayed by each probe to calculate the temperature difference, then cool the machine to 0 ℃, keep it warm for 30 minutes, observe the temperature displayed by each probe to calculate the temperature difference, and continue to cool the machine to -50 ℃, keep it warm for 30 minutes, and observe the temperature displayed by each probe to calculate the temperature difference.

3. In situ sterilization test

After cleaning the drying oven, place the biological indicator made from thermophilic spore bacteria on the shelves of each layer in the drying oven. When the temperature rises to 121 ℃ and the pressure reaches 0.11MPa, hold for 30 minutes to remove the biological indicator, and directly place it at 56 ℃~60 ℃ for 24-48 hours of cultivation. Then, take it out and judge the sterilization effect based on the color reaction. After cultivation, keep it purple to be qualified for sterilization; If it turns yellow, it is judged as unqualified sterilization.

4. Noise test

The measurement points are arranged along the periphery of the freeze-drying machine, generally taking four positions on the front, back, and sides of the equipment as standard measurement points. Add an auxiliary measuring point position every 5m around the perimeter. When the difference in noise measurement values between adjacent measuring points is greater than 5dB (A), an auxiliary measuring point position should be added between the measuring point positions.

The height of the measuring point from the ground is 1.55m ± 0.0075m, and the horizontal distance from the periphery of the freeze-drying machine is 1m.

5. Vacuum leakage rate test of freeze-drying machine

When the pressure inside the drying oven and water vapor condenser reaches 5Pa, close the isolation valve and vacuum pump to maintain pressure for 30 minutes. Record the vacuum gauge value and calculate the vacuum leakage rate according to the following formula.

Vacuum leakage rate=(X-5) × V solution/(30 × 60) ≤ 0.025Pa · m ³/s

In the formula: X - the vacuum pressure inside the drying oven after holding for 30 minutes, Pa；

V solution - net volume inside the drying oven, m³。

6. Water vapor trap water capture capacity test

Load 11kg/㎡ of water into a dedicated stainless steel tray, ensuring that each tray has an equal amount of water, and place it on the shelf of the drying oven for cooling. When the temperature of the drying oven reaches -50 ℃, the water vapor condenser begins to cool. When its temperature reaches -60 ℃, the vacuum pump is started to sublime the water. After 24 hours, the remaining water in the tray is weighed and the water capture capacity is calculated.

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