Anything that exists within the vacuum system that hurts or inhibits its proper function is considered a contaminant and must be addressed. Cleanliness is incredibly important to keep the chamber free of contaminants. High and ultra-high vacuum applications require parts that are free from volatile materials that would lead to contamination of the vacuum system.
There are two types of vacuum system contaminants:
- Contaminants that result in undesirable deposits within the system and cannot be pumped away.
- Contaminants that result in additional partial pressure that enter the system as a gas and can be pumped away.
If your system won’t pump down to a specified pressure the residual trapped gasses within the chamber are considered contaminants. However, contamination of your system can also happen due to the introduction of non-gaseous particles as well as contamination that can occur during normal operation of the system.
What is the primary source of vacuum contamination?
O-rings are most often the primary source of contamination in any vacuum system. An unprocessed, or “raw”, O-ring will contain a great deal of water which is chemically formed during the manufacturing process. Additional solvents and plasticizers with low vapor pressures will also likely be present. These contaminants will gradually come to the surface, desorb (outgass), and be pumped-away as a gas if they can reach the chamber. The higher the load the longer this will take and the potential for process contamination will grow. Water vapor in a virtual leak pocket will usually desorb then resorb on another surface, over and over, since it cannot be pumped away as it rarely reaches the chamber proper.
How can this problem be solved?
O-ring generated contamination can be avoided by either cleaning the O-rings or vacuum baking them prior to installation.
The O-ring cleaning process for vacuum systems is designed to reduce or eliminate surface particulate contamination originating from injection-mold release agents and post-mold handling processes.
The vacuum baking process, also called bake-out, involves placing the parts into a chamber and heating them, under vacuum, to drive out gases and other contaminants trapped in the parts. The process utilizes high heat and removes surface water and residual volatile compounds that may still be on or inside of the O-ring from the manufacturing process. The bake-out basically artificially accelerates the process of outgassing; removing impurities and allowing the components to be installed immediately in ultra-high vacuum or ultra-high purity systems without any fear of contamination.
How can UC Components, Inc. help you?
- Cleaned O-Rings undergo UC Components’ proprietary cleaning process. All cleaning and packaging is performed in our certified Class 100/ISO Class 5 Cleanroom. This process is based on typical requirements for pre-cleaning elastomer seals prior to installation for vacuum service.
- Vacuum Baked O-Rings also go through our precision cleaning process. This is followed by an extended vacuum bake-out process designed to remove trapped water within the O-ring polymer. Vacuum baking reduces water vapor outgassing under vacuum by orders of magnitude. The primary gas load in most vacuum systems is water. Our vacuum baked O-rings are packaged in our Class 100/ISO Class 5 Cleanroom, nitrogen backfilled, and double bagged.
View our parts catalog online to find the components you need, request a quote, or contact us for more assistance or additional information. If you do not see the items that you need listed in our standard products, please give us a call! We may not stock it but we are happy to acquire and manufacture just about any fastener or O-ring that you need. Contact us today.