For the context of this discussion, the ‘leak detection’ activities performed or recommended are in relation to detecting very small leaks (e.g. 1x10-6 mbar*l/s) in a vacuum chamber. Since it is unlikely that a system is 100% ‘leak-free’, it is important to know the level to which leaks occur for operational safety and performance. Here are some of the questions you’ve asked:
1. What causes leaks?
A1. Many things can cause a leak such as improperly sealed connections, component failure, dirt or flakes across seals.
2. How do I know I have a leak and what signs am I looking for?
A2. If your system can’t pump down to its base pressure, then there is a chance you have a leak. If you pump down for an extended period of time and it does not get to base pressure, checking for a leak is a good next course of action.
3. How does Intlvac locate a leak?
A3. Intlvac utilizes helium leak detectors and residual gas analyzers to detect leaks. Most often a leak test will be conducted before operating the system. A residual gas analyzer can be added as a component to the system during initial construction or as an add-on afterwards.
4. What information do I need to locate a leak?
A4. Consider if there have been any recent changes to the machine such as opening/closing chamber doors or conducting maintenance on seals and flanges. If something has recently been stirred and the system used to pump down to the desired pressure but it no longer does, the chance is great that whatever was modified may be connected to the newly discovered leak.
5. What can interfere with leak detection?
A5. You need to get the machine down to a certain pressure to begin conducting leak detection tests. Mass spectrometers, which are the main sensor unit in both the helium leak detector and a residual gas analyzer, require certain levels of vacuum to operate. Residual gas analyzers require much lower vacuum pressures than helium leak detectors for operation.
Another factor that can interfere with helium leak detection is if helium permeable materials are included in the construction of system units. Helium can diffuse through these materials giving the appearance of a leak where there is actually none. In addition, drafty rooms can impact leak detection as air currents spread helium around.
6. How long does it take to detect a leak?
A6. This will depend on how obvious the leak is and the size of the system. More complex systems may have more ports or vacuum connections to check. Depending on how much investigation is required, the detection of a leak can happen quickly or take quite some time. Identifying the source of a leak is like a treasure hunt. Often ‘trial and error’ is what it takes to pin point the cause and rectify it.
7. What equipment is required to detect a leak?
A7. A helium leak detector such as Leybold’s Phoenix suite of leak detectors are a quality solution used by Intlvac. A residual gas analyzer is another piece of equipment that can be added to a system to identify the various gases present in the system and their concentrations.
Additional Research on leak detection: https://www.vacuumscienceworld.com/vacuum-leak-detection#helium_tests