How to Select a High Vacuum Pump, Part 1: Overview
To determine the most appropriate vacuum pumping system for your application, it's important to know what types of vacuum pumps are available, what are their capabilities, and how they are different. In the high technology vacuum world there are three fundamental types of pumps: Positive Displacement, Momentum Transfer and Entrapment.
Positive Displacement Pumps allow the gas in the chamber being evacuated to first expand into a larger volume, then a small part of this volume is isolated and removed to the atmosphere, leaving behind a slightly reduced pressure in the chamber. “Dry” mechanical pumps, which became popular in the late 1980s, fall in this category and are still extremely popular, especially in applications where the process is sensitive to particulates and/or back-streaming oil. However, they are also noisier and more expensive than traditional oil-sealed pumps.
Momentum Transfer Pumps use either multiple spinning blades or the energy in a flow of liquid to sweep gas molecules out of the chamber, thus continuously reducing chamber pressure.
Entrapment (or Capture) Pumps do not exhaust the gas from a chamber to the atmosphere; but use a variety of means to capture gas molecules in a solid or adsorbed state. As gas molecules are captured, the pressure in the chamber is reduced.
Within these three categories of vacuum pumps there are a variety of choices. The most common examples of each category include:
Positive Displacement
Piston Pumps
Rotary Vane Pumps
Roots Blowers
Screw Pumps
Scroll Pumps
Diaphragm Pumps
Momentum Transfer
Turbomolecular Pumps
Molecular Drag Pumps
Diffusion Pumps
Entrapment
Cryo Pumps
Ion Pumps
This post was authored by Michael A. Grandinetti. You can learn more about Mike's background at http://www.linkedin.com/in/michaelgrandinetti1
IES Technical Sales is a value added technical sales, distribution, and solutions provider serving the high technology vacuum, plasma/thin film, temperature, fluid handling and metrology markets.