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What is the role of gas in vacuum pumps
Date: 2024-12-25Read: 2
I believe many people will see gas ballast in the instructions or illustrations of some oil sealed vacuum pumps. For example, the vacuum performance of rotary vane vacuum pumps may have two types: one is the value with gas ballast on, and the other is the value without gas ballast on. What role does the town of Qi play in this?
RZ 6 rotary vane pump
When it comes to gas towns, we need to talk about permanent gases and condensable gases. Some gases in our daily life and work, such as oxygen, nitrogen, hydrogen, methane, and helium, are inert gases that cannot be compressed and liquefied at room temperature. We call them permanent gases. On the other hand, the most common gases such as water vapor can be liquefied by compression, which we call condensable gases.
Whether it is an oil sealed vacuum pump or a dry vacuum pump, in the process of extracting condensable gases, once the pressure of the extracted gas exceeds the saturated vapor pressure of the gas at that time, condensation of condensable gases will occur. And for oil sealed vacuum pumps, due to the presence of lubricating oil in the pump chamber, when condensable gases condense, the liquefied gases will cause pump oil pollution, and over time, pump oil emulsification will occur, causing it to lose its lubrication and protection function; On the other hand, the condensed gas will evaporate again when returning to the low-pressure end, causing a decrease in the vacuum performance and pumping efficiency of the vacuum pump. Qizhen is designed to address the issue of oil sealed vacuum pumps.
Its working principle is also relatively simple, that is, when the partial pressure of condensable gas exceeds the saturation vapor pressure of the gas but the overall pressure in the pump chamber does not reach the exhaust pressure, dry permanent gas is timely filled through gas ballast to advance the overall pressure in the pump chamber to the exhaust pressure for discharge, thereby preventing the condensation of condensable gas. During the emission process, the permanent gas filled will also be discharged along with the gas in the original pump chamber.
The above is the role of gas Town in oil sealed vacuum pumps. But even with the presence of gas Town, oil sealed vacuum pumps are only suitable for extracting a certain amount of condensable gas in the medium environment. Once a large amount appears, efficiency cannot be guaranteed. Dry vacuum pumps may also experience gas condensation, but due to the absence of pump oil in dry vacuum pumps, their ability to remove condensable gases is superior to various types of oil sealed vacuum pumps.