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Why can sealing oil limit the performance of a rotary vacuum pump?
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vacuum technology
Diagram of a McLeod gauge.
In an oil-sealed rotary pump, the ultimate pressure is restricted by leakage between the high- and low-pressure sides of the device. This limitation is primarily caused by two factors related to the sealing oil:
- Gas and Vapor Carryover: Gases and vapors become dissolved in the sealing oil and subsequently flash off when they are exposed to the low-pressure environment at the pump's inlet.1
- Oil Decomposition: The oil may undergo decomposition when it comes into contact with hot spots created by friction within the pump.1
These processes introduce contaminants into the vacuum system, preventing the pump from reaching lower pressures.1