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Vacuum Pump: Working Principles & Classifications

A vacuum pump works by removing gas molecules from an enclosed space to create a partial or near-vacuum. This is achieved by creating a pressure difference between two areas, causing gas molecules to move from the area of higher pressure to the area of lower pressure. This process continues until the desired level of vacuum is reached. All types of vacuum pumps operate on this basic principle


There are several types of vacuum pumps, each with its own advantages and limitations. Some of the main types of vacuum pumps include:


  1. Gas transfer pump

    1. Kinetic/Momentum pump

      1. Turbomolecular pump

      2. Diffusion pump

    2. Positive displacement pump

      1. Liquid ring pump

        1. Water ring pump
        2. Oil ring pump

      2. Turbomolecular pump

      3. Rotary vane pump

      4. Piston pump

      5. Diaphragm pump

  2. Entrapment pump

    1. Cryogenic pump

    2. Sorption pump

  3. Combination pump

    1. Hybrid pumps (Combination of a positive displacement pump and a turbomolecular pump)

    2. ion pumps (Combination of a high-vacuum pump and an ionization chamber)


GAS TRANSFER VACUUM PUMP is a type of vacuum pump that is designed to transfer gas from one location to another, without compressing or significantly altering the gas composition. These pumps are commonly used in applications such as gas sampling, gas analysis, and gas transfer in chemical or pharmaceutical processes. Gas transfer vacuum pumps typically operate by creating a low-pressure region at the inlet port of the pump, which draws gas into the pump. The gas then passes through the pump and is discharged at the outlet port, where it can be directed to the desired location or process. Unlike other types of vacuum pumps that compress gas to create a vacuum, gas transfer pumps are designed to maintain the gas composition and pressure as much as possible. Gas transfer vacuum pumps can be further classified into different types, depending on the specific operating principle used. For example, membrane pumps use a thin, flexible membrane to move gas, while sorption pumps use a material such as activated charcoal to adsorb gas molecules and transfer them to a different location. Overall, gas transfer vacuum pumps play an important role in many industrial and laboratory applications that require the transfer of gas without significant alteration of its composition or pressure.


POSITIVE DISPLACEMENT PUMPS work by trapping gas molecules in a confined space and then reducing the volume of that space to create a vacuum.


MOMENTUM/KINETIC TRANSFER PUMPS work by transferring gas molecules from the inlet to the outlet using high-speed jets of fluid or rotating blades.


ENTRAPMENT PUMPS work by capturing gas molecules on a surface or in a solid or liquid medium.


COMBINATION PUMPS combine two or more types of pumps to achieve higher vacuum levels or to overcome the limitations of a single pump type.


The choice of vacuum pump depends on the application, the desired vacuum level, the type and volume of gas being pumped, and other factors.


Vacuum pumps are used to create a range of vacuum levels, from low vacuum to ultra-high vacuum. The pressure range of a vacuum pump depends on the type of pump and its design. Here are some common pressure ranges for different types of vacuum pumps

  • Positive displacement pumps can create pressures in the range of 10^-3 to 10^-6 torr.

  • Momentum transfer pumps can create pressures in the range of 10^-9 to 10^-12 torr.

  • Entrapment pumps can create pressures in the range of 10^-3 to 10^-11 torr, depending on the type of pump and the sorbent material used.

  • Combination pumps can create pressures in the range of 10^-9 to 10^-12 torr, depending on the type and combination of pumps used.


It's worth noting that achieving a specific pressure level requires careful selection and configuration of the vacuum system components, including the pump, the vacuum chamber, and the associated hardware. Other factors such as outgassing, leaks, and contamination can also affect the ultimate pressure level that can be achieved.


Generally Liquid Ring or Rotary Vane vacuum pumps are used in sugar refining process for Vacuum-Condenser System. As these can create high vacuum, several hundred mmHg gauge pressure.



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