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Asked: March 6, 2021In:
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pump failures
  1. VacuumFurnaces.com Answers
    What are some common vacuum furnace pumping system failures and their solutions?

    For the many vacuum furnaces in use around the world, the vacuum pumping system is a critical component. To get the best value from the vacuum furnace system and to extend its useful life, the regular and careful maintenance of the various vacuum pumps is of utmost importance.  Here are two resourceRead more

    For the many vacuum furnaces in use around the world, the vacuum pumping system is a critical component. To get the best value from the vacuum furnace system and to extend its useful life, the regular and careful maintenance of the various vacuum pumps is of utmost importance. 
    Here are two resources that delve deeply into this question, courtesy of Solar Atmospheres and Bill Jone.
    This PDF published by Solar Atmospheres Inc. and a Youtube Video presented by the legendary founder of Solar Atmospheres, Bill Jones

    SOURCE: Solar Atmospheres Inc. https://solaratm.com/

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Asked: March 3, 2021In:
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After installing new (sometimes calibrated) thermocouples (i.e. type K/S/R), they start to deviate over time. What can be the cause of that.

temperature deviation
  1. Greg Kimble

    Time and temperature have a way of making things deteriorate.  Vacuum also can present a problem for the materials (constituents) of the thermocouple, specifically relating to the vapor pressure of the materials.

    Time and temperature have a way of making things deteriorate.  Vacuum also can present a problem for the materials (constituents) of the thermocouple, specifically relating to the vapor pressure of the materials.

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Asked: March 1, 2021In:
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cryogenic mediumliquid nitrogen
  1. VacuumFurnaces.com Answers
    This answer was edited.

    Liquid nitrogen cold traps prevent products arising during the equipment operation from passing from the chamber into the pump where they could either contaminate the pump or cause the breakdown of the pump fluid. In either case, severe loss of efficiency and poor vacuum levels result. In the examplRead more

    Liquid nitrogen cold traps prevent products arising during the equipment operation from passing from the chamber into the pump where they could either contaminate the pump or cause the breakdown of the pump fluid. In either case, severe loss of efficiency and poor vacuum levels result. In the example shown the diffusion pump was only capable of reaching 4 x 10-3 Torr rather than the typical 1 x 10-5 Torr range achieved with a clean pump. In addition, these types of cold traps prevent backstreaming of the pump.

    SOURCE: Cold Traps / VAC AERO International Inc.

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Asked: March 1, 2021In:
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evacuationhigh vacuum valve
  1. Answer it Forward Challenge Official Account of VacuumFurnaces.com

    Using the roughing pump to evacuate the vacuum chamber before opening the high vacuum (gate) valve is necessary for several reasons related to vacuum efficiency, protection of equipment, and process integrity: 1. Prevent Overloading the High-Vacuum Pump: High-vacuum pumps, such as turbomolecular orRead more

    Using the roughing pump to evacuate the vacuum chamber before opening the high vacuum (gate) valve is necessary for several reasons related to vacuum efficiency, protection of equipment, and process integrity:

    1. Prevent Overloading the High-Vacuum Pump:
    High-vacuum pumps, such as turbomolecular or diffusion pumps, are designed to operate at low pressures and cannot handle atmospheric pressure or high-pressure environments. Starting with a high chamber pressure could overload the pump, potentially damaging it or drastically reducing its performance.

    2. Maintain Efficiency and Vacuum Quality:
    Roughing pumps (often rotary vane or scroll pumps) are built to handle the initial high pressures in the chamber and can quickly reduce the pressure to a level that high-vacuum pumps can manage efficiently. By using the roughing pump first, the chamber pressure is lowered to a point where the high-vacuum pump can operate effectively without being exposed to excessive gas load.

    3. Protect Sensitive Pump Components:
    High-vacuum pumps contain delicate, high-speed components (like rotor blades in turbomolecular pumps) that are susceptible to damage or wear if exposed to higher pressures. Bringing the chamber down to a low enough pressure with the roughing pump minimizes the stress on these sensitive components, extending their lifespan and reducing the risk of failure.

    4. Minimize Backstreaming and Contamination:
    If the high-vacuum pump is started with the chamber at a high pressure, there’s a greater likelihood of oil backstreaming in oil-sealed systems (e.g., diffusion pumps). Starting with a roughing pump allows a controlled transition to a lower pressure, where the high-vacuum pump can operate without excessive backstreaming risk.

    5. Ensure Process Stability and Product Quality:
    For processes that require stable, high-purity vacuum levels (such as heat treating, coating, or etching), gradual evacuation through the roughing stage reduces contaminants and moisture in the chamber. This provides a cleaner start for the high-vacuum pump, leading to more consistent and reliable results.

    In summary, using the roughing pump first lowers the pressure safely and efficiently, protects the high-vacuum pump from overload, and maintains vacuum quality, which is essential for the performance and longevity of the vacuum system.

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