(I) Performance index of vacuum pumping speed
The time for the vacuum system of the lyophilizer to pump from atmospheric pressure to 10Pa should not exceed 30min.
(B) the selection principle of vacuum pump
① The ultimate vacuum of the selected main vacuum pump should be 1 to 2 orders of magnitude higher than the ultimate vacuum required by the lyophilizer. Pharmaceutical freeze-drying generally requires a limit vacuum of 1 ~ 5Pa, and the limit vacuum of the main vacuum pump selected should be higher than 1X10-1 ~ 1X10-2Pa. Rotary vane pump, slide valve pump, roots pump, oil booster pump are all available.
② The working vacuum degree of the freeze-drying box is 4 ~ 4OPa, which should be within the optimal pumping pressure range of the main vacuum pump.
③ The vacuum pump used by the lyophilizer should also be able to remove some water vapor, or it can be adapted to be mixed with water vapor by the pumped gas.
(III) Calculation of pumping rate
The freeze-drying machine has a pre-pumping time requirement. This time requirement is very important when the cold trap and the freeze-drying box share a refrigerator. Failure to meet the requirements may cause the pre-frozen product to melt. If the vacuum condenser (cold trap) is used for cooling while the lyophilizer can still be kept cold at low temperature, this time requirement is not so important. In other words, the required time can be appropriately extended, but this has a slight impact on the performance of the freeze dryer.
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