For a leak test in vacuum systems, an acceptable vacuum level generally depends on the type of application and the sensitivity required. In most industrial settings, including vacuum furnaces for heat treating tool steel, the following guidelines can be considered: Rough Vacuum Testing: In rough vacRead more
For a leak test in vacuum systems, an acceptable vacuum level generally depends on the type of application and the sensitivity required. In most industrial settings, including vacuum furnaces for heat treating tool steel, the following guidelines can be considered:
- Rough Vacuum Testing: In rough vacuum systems (pressures above 1,000 microns or 1 Torr), an acceptable leak rate could be around 50–100 microns per minute of pressure rise after isolating the system. This is often used in preliminary leak tests before achieving high or ultra-high vacuum.
- High Vacuum Systems: In high vacuum systems (pressures below 10 microns or 0.01 Torr), an acceptable leak rate is typically much lower, often around 5 microns per minute or less. This is crucial for heat treatment applications where minimal oxidation and contamination are required.
- Ultra-High Vacuum: For applications that require ultra-high vacuum (below 1 micron or 0.001 Torr), the leak rate must be extremely low, often specified as less than 1 micron per hour. Leak rates here are typically measured using helium mass spectrometry rather than simple pressure rise tests.
Practical Example for Vacuum Furnaces
In your case, where you oversee vacuum furnaces for heat treating, maintaining a leak rate of 10 microns per minute or less would generally be acceptable, especially if high vacuum is necessary for preventing oxidation of tool steels. This ensures that any leak is small enough to not significantly impact vacuum quality or process outcomes during typical operating cycles.
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Finding leaks in vacuum furnaces is a task that few people look forward to, however it is important and necessary. Leaks happen almost always and can occur suddenly or develop over time. They can damage both the material being heat treated as well as internal furnace components. When left uncheckedRead more
Finding leaks in vacuum furnaces is a task that few people look forward to, however it is important and necessary. Leaks happen almost always and can occur suddenly or develop over time. They can damage both the material being heat treated as well as internal furnace components. When left unchecked leaks will stop the furnace from pumping down and will compromise the heating elements. Small leaks often go undetected since the pumping system can overcome them, but they can still cause continuous and eventually catastrophic damage. It is therefore highly recommended that routine leak checking and repair be a part of any good preventative furnace maintenance program.
An Excerpt: “Why is helium used to detect leaks? Helium is used as a tracer gas to detect leaks for several reasons. These include the fact that it constitutes only ~ 5 ppm in air so that background levels are very low. Helium has also relatively low mass so that it is ‘mobile’ and is completely inert/non-reactive. Helium is also non-flammable and generally widely available and low cost. This association with helium is one of the reasons why one of the most accurate and rapid leak detection methods employs helium as the tracer gas and a mass spectrometer for the analyzing/measuring. Furthermore, helium is chosen as a tracer gas because it is light, very quick, and absolutely harmless.” >> Continue Reading
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