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Asked: July 26, 2020In:
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high-vacuum pumproughing pump
  1. Answer it Forward Challenge Official Account of VacuumFurnaces.com

    A roughing pump and a high vacuum pump work together in a sequence to achieve and maintain very low pressures, necessary for vacuum furnace operations like those you oversee. Here’s how they work in tandem: Initial Pumping with Roughing Pump: The roughing pump (typically a rotary vane or scroll pumpRead more

    A roughing pump and a high vacuum pump work together in a sequence to achieve and maintain very low pressures, necessary for vacuum furnace operations like those you oversee. Here’s how they work in tandem:

    1. Initial Pumping with Roughing Pump: The roughing pump (typically a rotary vane or scroll pump) is responsible for reducing the pressure from atmospheric levels down to an intermediate vacuum level, usually around 10⁻³ to 10⁻⁴ mbar. The roughing pump is not capable of achieving ultra-low pressures by itself, but it efficiently brings the pressure down to a point where a high vacuum pump can take over.
    2. Transition to High Vacuum Pump: Once the pressure reaches this intermediate level, the high vacuum pump (such as a diffusion pump, turbo molecular pump, or cryopump) takes over. High vacuum pumps are designed to reach significantly lower pressures, often in the range of 10⁻⁶ mbar or lower. They cannot start directly at atmospheric pressure, which is why the roughing pump is essential for initial pressure reduction.
    3. Achieving High Vacuum: The high vacuum pump continues to evacuate the chamber, bringing the pressure down to the ultra-low vacuum levels required for high-temperature and contamination-sensitive processes, such as those used for processing tool steels.
    4. Ongoing Support: During operation, the roughing pump often continues to support the high vacuum pump by managing the backing pressure (the exhaust) of the high vacuum pump. This prevents any backflow that could compromise the vacuum quality.

    In essence, the roughing pump and high vacuum pump create a “two-stage” vacuum process, with the roughing pump handling the initial load and the high vacuum pump achieving the precise, low-pressure environment needed for applications like heat treatment.

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Asked: July 26, 2020In:
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rotary vane pump
  1. Answer it Forward Challenge Official Account of VacuumFurnaces.com

    A rotary vane vacuum pump operates by trapping air and other gases within a chamber, then compressing and expelling them to create a vacuum. Here’s a breakdown of the process: Chamber and Rotor Design: The pump consists of a cylindrical chamber with an off-center rotor inside. The rotor has severalRead more

    A rotary vane vacuum pump operates by trapping air and other gases within a chamber, then compressing and expelling them to create a vacuum. Here’s a breakdown of the process:

    1. Chamber and Rotor Design: The pump consists of a cylindrical chamber with an off-center rotor inside. The rotor has several vanes (typically two or more) that slide in and out of slots along its edges.
    2. Rotating Motion: When the rotor spins, centrifugal force pushes the vanes outward so that they contact the chamber wall, creating small, isolated compartments of air between each vane.
    3. Trapping the Air: As the rotor turns, air enters the chamber through an intake port and gets trapped between two adjacent vanes. The rotor’s rotation compresses this trapped air as it moves it toward the exhaust port.
    4. Compression and Exhaust: The compartment carrying the air gradually shrinks as it nears the exhaust port. This shrinking action compresses the air, which is then expelled through the exhaust port, creating the vacuum.
    5. Oil Lubrication: Rotary vane pumps are typically lubricated with oil to reduce friction, cool the components, and form a tight seal between the vanes and the chamber walls, improving the pump’s efficiency.
    6. Continuous Process: The vanes continuously spin, trapping, compressing, and expelling air, which allows the pump to create a stable, consistent vacuum.

    Rotary vane pumps are often used in applications where moderate vacuum levels are required and can be ideal in industrial settings, including vacuum furnaces, due to their reliability and efficiency.

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Asked: July 26, 2020In:
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rotary piston vacuum pump
  1. VacuumFurnaces.com Answers

    A rotary piston pump operates using a rotary mechanism where a piston is housed within a larger cylinder. The piston is typically eccentrically mounted, which means it is not centered within the cylinder. As the piston rotates, it creates expanding and contracting volumes within the cylinder. Here'sRead more

    A rotary piston pump operates using a rotary mechanism where a piston is housed within a larger cylinder. The piston is typically eccentrically mounted, which means it is not centered within the cylinder. As the piston rotates, it creates expanding and contracting volumes within the cylinder.

    Here’s a step-by-step explanation of the process:

    1. Intake Stroke: As the piston moves away from the inlet port of the pump, it creates a vacuum. This vacuum causes the inlet valve to open due to the pressure difference, allowing the fluid to enter the pump.
    2. Compression Stroke: As the piston continues to rotate, the volume of the fluid chamber decreases. This action compresses the fluid, increasing its pressure.
    3. Discharge Stroke: When the fluid pressure exceeds the pressure in the discharge line, the outlet valve opens, and the fluid is forced out of the pump.
    4. Return Stroke: After the discharge, the piston continues to rotate back towards the inlet port, and the cycle repeats.

    This type of pump is known for its precision and ability to handle a wide range of viscosities, making it useful in applications such as fuel injection, hydraulic systems, and in the chemical industry where precise fluid handling is necessary.

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Asked: July 26, 2020In:
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How does a Residual Gas Analyzer (RGA) work?

working principle
  1. VacuumFurnaces.com Answers
    This answer was edited.

    A residual gas analyzer (RGA) is a type of mass spectrometer used primarily to identify and quantify the gases present in a vacuum system. It allows for the analysis of gas species in the low-pressure environments often required in high-tech industries such as semiconductor manufacturing and surfaceRead more

    A residual gas analyzer (RGA) is a type of mass spectrometer used primarily to identify and quantify the gases present in a vacuum system. It allows for the analysis of gas species in the low-pressure environments often required in high-tech industries such as semiconductor manufacturing and surface science. Here is a simplified description of how an RGA works:

    Ionization of Gas Molecules: Gas molecules within the RGA’s sampling volume are ionized, usually by electron impact. This means that electrons are fired at the gas molecules by an electron gun, knocking off an electron and creating positively charged ions.

    Mass Analysis: The ions are then directed into a mass filter, which is often a quadrupole mass filter. A quadrupole consists of four parallel metal rods, with each opposing rod pair connected to a radio frequency (RF) voltage with a direct current (DC) offset. The RF and DC fields are applied to the rods in such a way that only ions of a specific mass-to-charge ratio (m/z) can pass through the filter at any one time, with other ions being deflected and lost. By scanning through a range of RF and DC settings, ions of different m/z can be selectively filtered through the quadrupole, allowing the RGA to scan across a range of masses and thus detect multiple gas species.

    Detection of Ions: The ions that pass through the mass filter reach a detector, which is often a Faraday cup or a secondary electron multiplier (SEM). These devices generate a signal proportional to the number of ions hitting them. The detector’s output is then processed and read out as a mass spectrum. Peaks on the spectrum correspond to the m/z of the ions, which can be used to identify the gas species. The height or area of the peak is proportional to the concentration of that species in the gas mixture.

    Data Interpretation: The resulting data are interpreted to determine the types and quantities of gases present in the vacuum system. RGAs are crucial for quality control and system maintenance in vacuum systems, as they help identify contaminants, leaks, and outgassing sources which may compromise the integrity of the vacuum environment or the processes occurring within it.

    For a more detailed explanation visit: Residual Gas Analysers – VAC AERO International

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pirani gauge
  1. Answer it Forward Challenge Official Account of VacuumFurnaces.com

    A Pirani gauge is a thermal conductivity vacuum gauge used to measure low to medium vacuum levels, generally from about 0.5 Torr down to 10⁻⁴ Torr. Its operation is based on the principle that the thermal conductivity of gases changes with pressure. Working Principle 1. Heating Element: The gauge coRead more

    A Pirani gauge is a thermal conductivity vacuum gauge used to measure low to medium vacuum levels, generally from about 0.5 Torr down to 10⁻⁴ Torr. Its operation is based on the principle that the thermal conductivity of gases changes with pressure.

    Working Principle

    1. Heating Element: The gauge consists of a thin filament, usually made of tungsten or platinum, which is heated by a constant electric current. When the filament is in a vacuum, the heat dissipates through conduction to the surrounding gas molecules.

    2. Thermal Conductivity: As gas pressure decreases, fewer gas molecules collide with the filament, resulting in less heat being conducted away. At higher pressures, more gas molecules are present, leading to more efficient heat transfer.

    3. Measuring Resistance Change: As the filament heats up, its electrical resistance changes. This resistance variation is measured and correlated to the gas pressure. When the vacuum level is high (fewer gas molecules), the filament stays hotter, leading to higher resistance. When the pressure is higher, the filament cools more due to increased molecular collisions, leading to lower resistance.

    4. Calibration: The gauge is calibrated to translate this resistance into a pressure reading. Pirani gauges are generally calibrated for specific gases (usually air or nitrogen), so the accuracy can vary with different gases due to differences in thermal conductivity.

    Applications and Limitations

    • Applications: Pirani gauges are commonly used in vacuum systems that operate in the low to medium vacuum range, such as in vacuum furnaces, coating processes, and other industrial applications.
    • Limitations: The accuracy of a Pirani gauge can be affected by changes in gas composition, as different gases have different thermal conductivities. Additionally, they are less effective at very high vacuums (e.g., below 10⁻⁴ Torr), where other types of gauges like ionization gauges are preferred.
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