Vacuum system is one of the important parts of the freeze dryer, generally including rotary vane vacuum pump or dry vacuum pump and roots pump.
The vacuum system is connected with the condenser through a stainless steel pipeline. A pneumatic butterfly valve is installed near the condenser to separate the condenser from the vacuum system.
Dry pump control process:
Cooling stage of the rear tank: the dry vacuum pump is preheated for 15 minutes, and the nitrogen protection valve of the vacuum pump, the purge valve of the vacuum pipeline, the cooling water valve of the vacuum pump group (gv80) are opened at the same time. The preheating time is until the nitrogen protection valve of the vacuum pump, the purge valve of the vacuum pipeline are closed, and then the small butterfly valve is opened.
Start up of dry vacuum pump: judge that the temperature of the rear box is lower than – 45 ℃, set the time for holding the rear box until it reaches, preheat the dry vacuum pump for 15 minutes, and open the small butterfly valve to start pre vacuumizing. When the preheating time is up, close the nitrogen protection valve of vacuum pump and the purge valve of vacuum pipeline.
Re pressure plug stage: when the small butterfly valve is closed and the vacuum pump is open, the dry air supply valve of the main intake valve can be opened.
Dry vacuum pump stop:
1. Close the small butterfly valve and the vacuum pump closing command, judge whether the small butterfly valve closing signal is in place, open the nitrogen protection valve of the vacuum pump, open the vacuum pipeline purging valve (whether the vacuum pipeline purging valve is provided by the equipment itself), take the vacuum pump closing command as the timing starting point for 15min, and then close the pump closing valve.
2. If the small butterfly valve is not closed, close the small butterfly valve immediately, stop the dry pump, then close the small butterfly valve, close the vacuum pump, judge whether the small butterfly valve closing signal is in place, open the nitrogen protection valve of the vacuum pump, open the vacuum pipeline purging valve (whether the vacuum pipeline purging valve is equipped with the equipment itself), and close the pump and valve 15 minutes later with the vacuum pump closing command as the timing starting point.
3. In the process of automatic operation of refrigeration, the vacuum pump shall be started immediately when power is cut off and power is supplied again. Vacuum line purge valve, power down to maintain. Power off automatically and then call again, pop up a dialog box to confirm whether to preheat, yes preheat for 15 minutes, no directly open.
In the automatic process: judge the automatic start flag bit, select backup or manually stop a group, and start and stop without delay if nitrogen is not purged. Stop the dry pump directly during backup, and start the dry pump directly again. The second dry vacuum pump is started after another dry pump is turned off and delayed for 10s, and the two dry vacuum pumps are purged together.
The function of the vacuum system is to establish a vacuum and provide the environment and conditions for the sublimation of ice. The vacuum degree of vacuum system directly affects the sublimation rate of products, and the vacuum system requires a low leakage rate. The precision of vacuum control directly affects the operation of pharmaceutical process.
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