Updated: November 12, 2024
Delicate processes such as mass spectrometry, electron microscopy, coating, and deposition require efficient, pristine, and well-managed vacuum systems. With almost 60 years of experience in vacuum manufacturing, we have identified several simple practices that can prevent major issues in vacuum systems. Here are ten things you can do to ensure your system operates successfully for efficient data collection and accurate results.
1. Handle All Vacuum Components With Lint-free Kid Gloves
The main purpose of using a vacuum environment is to control environmental pressure and composition. Even though it may seem quicker to assemble or handle vacuum equipment with bare hands, it will introduce oils into your system that cause outgassing. This can prevent you from reaching your ultimate pressure and introduce cleaning difficulties – once a fingerprint is on, the location can be very hard to detect. For this reason, we suggest always handling your vacuum components with lint-free gloves.
If these are not available, surgical latex gloves are the next best choice. If bare hands cannot be avoided, immediately clean all “wetted” surfaces (with the exception of elastomeric seals) with isopropanol.
ANCORP vacuum components are always washed with a supersonic solution prior to being packaged, ensuring your products are vacuum-ready upon delivery!
2. Use Vacuum Grease Sparingly
Would you be surprised to learn that having too much of a good thing extends to vacuum grease? Vacuum grease is notorious for being over-applied and in improper places causing a suite of problems for vacuum users. It’s important to keep in mind that this grease is specially formulated to lubricate dynamic internal surfaces found on components such as linear motion feedthroughs and valve stems. That is, grease should be applied to rotating and moving elastomeric seals only and is not necessary for static seals.
After ensuring your vacuum part would benefit from vacuum grease, use the minimal amount necessary. Otherwise, thick layers of vacuum grease can become collection points for airborne contaminants and leech into your controlled environment. To minimize this risk, use vacuum grease sparingly and apply only the thinnest veneer possible.
3. Avoid Galling Bolts
Stainless steel bolts are prone to galling (cold welding) when installed into stainless steel bolt holes. This cold welding is due to friction and adhesion between the metal surfaces when they come into contact during bolt installation.
To prevent this, we recommend a graphite-based anti-seize compound and following the proper torque pressure for your installation. When higher torque is required, such as on metal seal (CF) flanges, we recommend using twelve-point bolts for installation. This will allow for more contact area between the wrench and bolt allowing for higher torque tolerance with decreased risk of galling. Always follow torque specifications when installing flanges.
4. Using the Proper Sealing Material
Every vacuum system relies on the proper sealing of different components to be fully functional. These connections can be joined by varying sealing methods depending on the various environmental requirements of your system such as vacuum level and temperature. Choosing the appropriate sealing material for your sealing method is critical in ensuring your system doesn’t experience a leak or other failure.
Metal seals are generally used on high-temperature or ultra-high vacuum (UHV) applications. Users of UHV chambers and systems tend to equip their systems with ConFlat (CF) flanges for this combination of requirements. The standard metal seal for CF flanges is oxygen-free high thermal conductivity copper (OFHC).
Elastomers can be used as a sealing material with great success for systems experiencing high vacuum duty cycles, like those in batch systems. Elastomeric seals are intended for high vacuum (HV) applications where the base pressure ranges from 10-3 to 10-8 Torr. There are several elastomeric seal materials—each with unique leak rate and temperature resistance characteristics. For detailed information between types of elastomer seals read our guide on FKM v FFKM in high vacuum applications.
When shopping for your vacuum system connections, pay special attention to specifications for temperature and pressure ratings, cross-referencing them with your system requirements.
5. Minimize Weld Seams and Joints Around Magnetically Sensitive Areas
Heat-affected zones from welding processes or cold-worked zones from machining processes often have higher magnetic permeabilities. If your application requires additional magnetic shielding, high permeability materials such as Mu-metal is recommended. Additionally, alternative metals such as titanium are a common build material for applications where magnetic sensitivity is a concern.
6. Trap Oil Presence in Hydrocarbon Sensitive Applications
Oil-sealed rotary vane pumps, lubricated turbo pumps, and diffusion pumps are commonly used to create and maintain environments in vacuum chambers. They accomplish this with great success; however, these pumps can also introduce hydrocarbons into a system through backstreaming. Backstreaming is when oil vapors and other contaminants migrate from the pump back into the chamber and is particularly problematic in sensitive applications where these hydrocarbons can affect product quality and data accuracy.
Consider adding a trap or filter to your system to prevent hydrocarbons from backstreaming into your vacuum chamber. Vacuum traps work by creating a physical or chemical barrier and are available in a variety of styles, such as cold traps, adsorption traps, and baffle traps. If you’re not sure where to start, we’ve prepared a detailed guide to vacuum traps to help you make your selection.
7. Avoid Trapped Volumes to Eliminate Virtual Leaks
Trapped volumes of gas lead to outgassing problems known as virtual leaks. The classic example of a virtual leak is the internally mounted threaded bolt. On a bolt with internal threads, there will always be a volume of air clinging to the microscopic space between the threads and the thread-bolt connection. In this instance, a vented bolt would eliminate the source of the virtual leak.
Minimizing complex internal geometries in vacuum components or using vented, smooth, or properly welding designs helps reduce the risk of virtual leaks. Externally welded lapped joints are another common example of poor vacuum design. Internal, butt welds are the way to go for vacuum and standard practice at ANCORP.
Virtual leaks can often be distinguished from real leaks or from permeation leaks by their unique signature as small spikes in gas analyzer data. Another technique is the rate of pressure rise method. In this method, a system is pumped down and then isolated. Pressure rise vs. time curve is computed. A virtual leak can be distinguished by its flat pressure vs. time curve. Pressure from a real leak will continue to rise until the outside chamber pressure is reached.
8. Install (CF) Copper Gaskets Properly
Leaks at metal gasket seals are a common reason for wasted time, often causing interruptions in runtime for needed maintenance. The easiest way to avoid this issue is proper installation. Copper gaskets should fit snugly in the counterbore surrounding the knife edge of the flange. During installation, the metal gasket should not be able to “wiggle” or move while the knife edge makes a seal. For added security, two grooves are machined into the flange face for gasket clamps to hold the metal gasket in place during vertical or upside-down installations. During the manufacturing process, these grooves may also be used as helium leak check ports.
On installation, flange bolts should be tightened in a “star” pattern to apply pressure evenly across the face. It’s important to note that under no circumstances should a copper gasket be reused. For detailed installation instructions and the CF torque guide, refer to our ConFlat flange installation guide.
9. Do Not Pressurize Viewports
When backfilling, venting, or breaking vacuum on a chamber with viewports, be sure that the chamber pressure does not exceed one atmosphere. When a vacuum viewport is placed under positive pressure, the window’s integrity is risked potentially introducing leaks or contaminants that can affect various readings and measurements in the system. Vacuum viewports are generally not rated for positive pressure with exceptions specified by the manufacturer.
Our inventory offers a wide range of vacuum windows designed for a variety of high—and ultra-high-vacuum applications. Browse our online store or contact us directly to view our variety of material and size options.
10. Partner with ANCORP for Quality Vacuum Components
Building a high-performance vacuum system starts with choosing a reliable, expert manufacturer. For complex systems, dedicated technical support will be essential to address flange compatibility, system requirements, and best practices tailored to your needs. ANCORP’s team of customer service professionals and technical sales engineers work closely with you to meet these critical requirements, ensuring your project’s success every step of the way.
With decades of experience in vacuum technology, ANCORP prioritizes quality, precision, and customer-focused support, equipping you with the expertise needed to make informed, confident decisions.