Working Principle And Classification of Vacuum Pumps in Yingtai Freeze Dryers

Working Principle and Classification of Vacuum Pumps in Yingtai Freeze Dryers

Types of Vacuum Pumps

Based on their working principles and structural characteristics, vacuum pumps in freeze dryers are primarily divided into oil-sealed vacuum pumps and oil-free vacuum pumps.

Oil-Sealed Vacuum Pumps

There are two types of oil-sealed mechanical vacuum pumps: rotary vane and slide valve. The most commonly used in freeze dryers is the rotary vane pump. The oil film in these pumps serves both as a seal and as lubrication between the various components. To improve the ultimate vacuum, typically two pumps are connected in series to form a two-stage pump.

In operation, the rotary vane vacuum pump compresses gases. If the gas contains a significant amount of water vapor, the vapor will condense into small water droplets and mix with the vacuum pump oil, causing the oil to emulsify and affecting the sealing performance of the pump, thus impacting its ultimate vacuum. To address this, oil-sealed vacuum pumps are equipped with a gas ballast valve. This valve allows the compressed gas to communicate with the external environment before compression is completed, reducing the compression ratio and thereby minimizing water ingress into the vacuum pump oil. The opening of the gas ballast valve can be adjusted or completely closed. When the gas ballast valve is opened, it lowers the ultimate vacuum of the vacuum pump and increases the consumption of vacuum pump oil.

Yingtai freeze dryers are equipped with an oil mist filter to protect the working environment from contamination.

Oil-Free Vacuum Pumps

Vacuum pumps that use working media within the pump chamber can cause contamination in the vacuum system due to the evaporation and diffusion of vapor molecules from the working media into the vacuum system. This is unacceptable for pharmaceutical machinery with strict requirements. However, dry pumps can operate without any working media.

Dry pump systems are clean evacuation systems, with no oil or other liquid media in the pump chamber, ensuring no contamination of the items within the evacuated container. The exhaust port does not emit oil mist, thus avoiding environmental pollution. They have strong extraction capabilities for condensable gases like alcohol and water vapor. Maintenance costs are low since they do not require oil to be added or changed. However, dry pumps are relatively expensive.

Dry pump systems are clean evacuation systems, with no oil or other liquid media in the pump chamber, ensuring no contamination of the items within the evacuated container. The exhaust port does not emit oil mist, thus avoiding environmental pollution. They have strong extraction capabilities for condensable gases like alcohol and water vapor. Maintenance costs are low since they do not require oil to be added or changed. However, dry pumps are relatively expensive.