Classification of vacuum pumps

Author: Ali Kosari Mehr

Classification of vacuum pumps

Vacuum pumps are usually selected according to their operational range, ultimate pressure achievable, physical/chemical process for pumping, pumping speed, weight, size, etc. In general, vacuum pumps can be divided into two categories:

Gas transfer pumps

These pumps per se can be classified into two subgroups:

1. Displacement pumps: The working mechanism of these pumps is based on the periodic change of their working volume. Hence, entering an operation volume, the gases are conveyed and evacuated from the pump. The pumps working by this means include the below-mentioned pumps.

• Piston oil pumps
• Single-rotor pumps including rotary water ring pumps, rotary oil pumps, dry rotary pumps, dry diaphragm pumps, dry piston pumps, and scroll pumps
• Two-rotor pumps including hook/claw pumps and Roots pumps
• Screw pumps

2. Kinetic pumps (or momentum transfer pumps): The working mechanism of a group of these pumps is based on the transfer of momentum from fast-moving surfaces to gas molecules. The pumps working by this means include the below-mentioned pumps.

• Turbomolecular pumps
• Regenerative pumps
• Drag molecular pumps

The working mechanism of the other group is based on molecular beams or fluid jets transferring their momentum to the pumped gas molecules. Usually, heavy fluid molecules are involved in the pumping media. Exemplifying the use of these pumping media, one can refer to jet fluid pumps – in particular, diffusion pumps and ejector pumps.

Capture pumps

The working mechanism of these pumps is based on adsorbing gas molecules into cold and chemically active surfaces. Electric pumping can be a means of improving this chemical sorption, which is based on getters. Notwithstanding, unlike the other pumps, the captured gas molecules remain inside the pumps, not leaving the vacuum system. The pumps working by this means include the below-mentioned pumps.

• Sublimation getter pumps
• Magnetic ion sputter pumps (diode configuration or triode configuration)
• Hybrid orbitron pumps
• Cryosorption pumps
• Cryogenic pumps

In the future, it will be attempted to briefly present the operating procedure of each vacuum pump.

References:

1. Bello I (2017) Vacuum and ultravacuum: Physics and technology. Vac Ultravacuum Phys Technol 1–1036. Webpage
2. Naik PK (2018) Vacuum : Science, Technology and Applications. Webpage