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Bryan R Cope
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Bryan R Cope
Asked: July 21, 2023In:
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We use Vac Aero furnaces with 6 bar quench to process tool steel and high speed steel. In the past week, both furnaces have been unable to reach the starting vacuum or loose vacuum during heat treating. I do have a leak ...

  1. Answer it Forward Challenge Official Account of VacuumFurnaces.com
    This answer was edited.

    It sounds like you're dealing with a tricky vacuum issue. Since you've already been leak-checking the furnaces and haven't found any significant leaks when they’re cold, a few potential factors to consider could be: Thermal expansion-related leaks: As the furnace heats up, thermal expansion may causRead more

    It sounds like you’re dealing with a tricky vacuum issue. Since you’ve already been leak-checking the furnaces and haven’t found any significant leaks when they’re cold, a few potential factors to consider could be:

    1. Thermal expansion-related leaks: As the furnace heats up, thermal expansion may cause small leaks to appear that aren’t detectable when the furnace is cold. Check for areas where seals or joints might be affected by high temperatures.
    2. Outgassing: Sometimes, when a furnace heats up, materials inside the furnace (including lining materials or residues) can outgas, leading to a loss in vacuum. Cleaning or baking out the furnace may help reduce this.
    3. Pump or valve issues: Since you’re having trouble reaching vacuum or maintaining it, your vacuum pumps or valves may need maintenance or replacement. Have you checked the functionality of your pumps (e.g., diffusion, turbomolecular, or backing pumps)? Pump oil contamination or wear may also cause degraded performance.
    4. Backstreaming of oil: If you’re using oil-based vacuum pumps, backstreaming (where oil vapor moves into the furnace chamber) can degrade vacuum quality. Check the pumps for signs of oil contamination.
    5. Quench systems: If there is an issue with your quenching system (since it uses high pressure), check the integrity of seals and valves related to the quench system as well, as it may interfere with vacuum integrity.

    Regarding hands-on help, you might consider contacting a vacuum furnace manufacturer for troubleshooting or a service technician visit. They have detailed knowledge and can offer specialized support for diagnosing and repairing the problem.

    Alternatively, if you’re looking for local or regional expertise, industrial furnace service providers specializing in vacuum furnaces can assist with diagnostics and repair.

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Bryan R Cope
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Bryan R Cope
Asked: March 2, 2023In:
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Replacing our hot zone in a 36 x 24 x 24 inch furnace.  The insulation is fiber. The furnace does high speed steel at 2175 F. What would be a typical burn in cycle?

  1. Raf Walczak

    Furnace burn out (a.k.a. thermal cleaning) cycles are important part of vacuum furnace maintenance. It is meant to reduce and outgas contaminants inside the heating zone and within the insulation. For new hot zone it is more related to drying, conditioning and outgassing the remaining resin from insRead more

    Furnace burn out (a.k.a. thermal cleaning) cycles are important part of vacuum furnace maintenance. It is meant to reduce and outgas contaminants inside the heating zone and within the insulation.

    For new hot zone it is more related to drying, conditioning and outgassing the remaining resin from insulation manufacturing processes. Every new furnace should be burned out at it’s nominal temperature and I’d say this rule should also apply to any hot zone replacement. Your hot zone supplier should be able to tell you the nominal temperature of the hot zone.

    Duration of burnout should be at least 2 hours at the temperature, however you may keep it longer if you see continuous improvement of furnace vacuum level.
    Slow cooling is recommended after burnout.

    IMPORTANT: The burn-out cycle is always performed with empty furnace. any tooling / fixturing and other equipment must be removed otherwise serious damage of furnace and tooling may occur.
    For your own safety you should follow the OEM manuals.

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MERT
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MERT
Asked: March 2, 2023In: , , ,
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I HAVE A CONTAMINATION PROBLEM WITH THE VACUUM FURNACE. WHEN I  LOAD CHARGE TOOL STEELS ARE TRANSFORMİNG THİS COLOUR. DOES ANY BODY HAVE AN IDEA? WHAT SHOULD BE THE FIRST STEP ?

  1. VacuumFurnaces.com Answers

    "When operating vacuum furnaces, situations may arise in which the hot zone and/or cold walls may become contaminated (Fig. Nos. 1 – 2). This can occur from a variety of sources: air leaks, outgassing from residues left on the parts as a result of the manufacturing or cleaning processes, vaporizatioRead more

    “When operating vacuum furnaces, situations may arise in which the hot zone and/or cold walls may become contaminated (Fig. Nos. 1 – 2). This can occur from a variety of sources: air leaks, outgassing from residues left on the parts as a result of the manufacturing or cleaning processes, vaporization of sensitive materials (e.g., chromium-bearing materials), process-induced contaminations such as carbon in the form of soot or tar, fluxes from brazing pastes, excess braze alloy as well as many other sources. Often times the work being processed is also affected (Fig. 3). The question becomes, how do we attempt to clean up our contaminated vacuum furnaces? >>>Read More

    Source: VAC AERO International

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Answer it Forward Challenge
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Answer it Forward Challenge
Asked: February 28, 2023In:
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There is a brazing vacuum furnace that we are currently using. We are experiencing various problems with it. We think that it is probably due to diffusion pump. All gaskets were renewed, difussion oil was replaced with new one. Control tests were ...

diffusion pump
  1. Answer it Forward Challenge Official Account of VacuumFurnaces.com
    This answer was edited.

    If your diffusion pump is not working properly, several potential issues could be affecting its performance. Here’s a list of common causes and diagnostic steps: 1. Insufficient Heating Issue: The diffusion pump relies on heating the oil to create vapor jets, which then carry away gases. If the heatRead more

    If your diffusion pump is not working properly, several potential issues could be affecting its performance. Here’s a list of common causes and diagnostic steps:

    1. Insufficient Heating

    • Issue: The diffusion pump relies on heating the oil to create vapor jets, which then carry away gases. If the heater is malfunctioning or not reaching the proper temperature, the oil won’t vaporize correctly.

    2. Cooling System Problems

    • Issue: Diffusion pumps require adequate cooling to condense oil vapors back to liquid form. If cooling is insufficient or blocked, the pump may overheat, leading to inefficient operation or even backstreaming of oil.

    3. Contaminated or Incorrect Diffusion Pump Oil

    • Issue: If the oil is degraded, contaminated, or the wrong type, it can cause backstreaming, poor performance, or even pump failure.

    4. Improper Venting or Isolation

    • Issue: If the pump is not properly isolated from the system or not vented correctly, it could allow air to enter, reducing the vacuum level.

    5. Faulty Diffusion Pump Valve or Interlock System

    • Issue: Sometimes, a malfunctioning valve or an interlock can prevent the diffusion pump from operating correctly. This can result in the pump not engaging properly or being stuck at a higher pressure.

    6. Leaks in the Vacuum System

    • Issue: Leaks in the system can prevent the diffusion pump from achieving low pressures. Even small leaks can significantly impact performance.

    7. Backstreaming of Oil

    • Issue: Backstreaming occurs when oil vapor moves in the opposite direction and can reach the vacuum chamber, contaminating the system and reducing pump effectiveness.

    8. Obstructions or Contamination in Pump Lines

    • Issue: Dirt, residues, or contaminants in the pump’s internal channels or outlet can reduce the efficiency of the vapor jet and restrict gas flow.

    9. Improper System Pressure Staging

    • Issue: Diffusion pumps are designed to work only within specific pressure ranges. Starting the diffusion pump while the chamber is at too high a pressure can impair its function.

    By working through these potential causes you can systematically eliminate common diffusion pump issues and restore efficient operation in your vacuum system.

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DSnell
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DSnell
Asked: January 22, 2023In:
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I have a Class 1 aluminum vacuum brazing furnace (per AMS2750 G) that has seven zone thermocouples. When performing a system accuracy test (SAT), must I verify all seven zone temperatures are within ±2° F of the SAT thermocouples installed ...

sattc
  1. Raf Walczak

    According to paragraph 3.4.1.2. of AMS2750G: "The SAT shall be performed on all control and recording systems required by the applicable instrumentation type, as well as any additional recording systems used for parts and raw material acceptance in each control zone of each piece of thermal processiRead more

    According to paragraph 3.4.1.2. of AMS2750G:
    “The SAT shall be performed on all control and recording systems required by the applicable instrumentation type, as well as any additional recording systems used for parts and raw material acceptance in each control zone of each piece of thermal processing equipment used for production heat treatments.”

    That means you should perform SAT on all control temperatures as well as any other temperature measurement system which are required by instrumentation type. For example Load thermocouples for instrumentation type A and B.
    SAT is not required for overtemp systems (if overtemp protection  is the only function of that system).

    Each of those ‘systems’ (Thermocouple, TC wires, feedthroughs, and measuring/recording instrument) should be within SAT tolerance (which is 2F for class 1 equipment) to their SAT sensor.

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