Can Roots blowers be used as vacuum pumps
Roots blower can be used as a vacuum pump, but it needs to meet specific conditions and be paired with appropriate system design. Here is a detailed answer:
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**1、 The principle of using Roots blower as a vacuum pump**
1. * * Working method**
-The Roots blower itself is a volumetric gas conveying equipment, which pushes gas from the inlet end to the outlet end through the rotation of the rotor.
-When it is connected in reverse (i.e. suction through the air outlet and exhaust through the air inlet), a negative pressure (vacuum) environment can be formed.
-But when used alone, its vacuum degree is limited (usually only able to reach * * -20kPa to -50kPa * *, which is about -0.2 to -0.5 bar).
2. * * Restrictive factors**
-* * No internal compression * *: The compression ratio of Roots blowers is low, making it impossible to achieve high vacuum like specialized vacuum pumps.
-Leakage gap: The small gap between the rotor and the casing can cause gas reflux, affecting the vacuum degree.
-Temperature rise issue: Prolonged vacuuming may cause thermal expansion of the rotor due to gas compression and temperature rise, exacerbating leakage.
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**2、 How to improve vacuum performance**
1. * * Equipped with a front-end pump (necessary measures)**
-Roots blowers usually require the use of rotary vane pumps, liquid ring pumps, or screw vacuum pumps to form a vacuum system.
-The front-end pump first pumps the system to a medium low vacuum (e.g. -90kPa), and then uses a Roots blower to pressurize and extract air, ultimately reaching a pressure range of -95kPa to -100kPa (5kPa to 0.1kPa).
-This combination can significantly improve the pumping efficiency and vacuum degree (commonly seen in industries such as industrial vacuum smelting and chemical engineering).
2. * * System optimization**
-Sealing Design: Using mechanical or dry gas seals to reduce gas leakage.
-Cooling measures: A cooler should be installed under high temperature conditions to prevent rotor deformation.
-Variable frequency control: By adjusting the speed to match the vacuum demand, it saves energy and avoids overload.
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**3、 Applicable scenarios**
1. * * Low vacuum requirement**
-Vacuum packaging (such as food and electronic products)
-Small central vacuum adsorption systems (such as glass handling, printing machines)
-Laboratory low vacuum environment (requires buffer tank)
2. * * Medium high vacuum system (requiring a pre pump)**
-Vacuum coating, vacuum drying
-Freeze drying equipment in the pharmaceutical industry
-Gas transportation in the semiconductor industry
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**4、 Comparison with professional vacuum pumps**
|* * Comparison item * * | * Roots blower as vacuum pump * * | * * Professional rotary vane vacuum pump * * | * Liquid ring vacuum pump * *|
|------------------|----------------------------|----------------------------|----------------------------|
|Ultimate vacuum degree * * | -50kPa~-90kPa (single machine) | -0.1Pa~-100kPa | -30kPa~-95kPa|
|* * Extraction rate * * | Medium to high flow rate | Small to medium flow rate | Medium flow rate|
|Corrosion resistance * * | Customizable stainless steel/coating | General | Suitable for corrosive gases (water sealed)|
|* * Maintenance cost * * | Low (oil-free design) | Requires regular replacement of rotor and oil | Requires handling of working fluid|
|* * Energy consumption * * | High (requires front stage pump) | Low | Medium|
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**5、 Precautions**
1. * * Dry smoking is strictly prohibited**
-If the extracted gas contains dust or easily condensable components, a filter or gas-liquid separator should be installed to avoid damaging the rotor.
2. * * Avoid overloading**
-When the vacuum degree approaches the limit of the fan, the motor current will sharply increase, and a pressure protection switch needs to be installed.
3. * * Selection suggestions**
-Single machine use: Only suitable for low vacuum scenarios (such as wastewater discharge from aquaculture ponds).
-High vacuum requirement: Must be equipped with a front-end pump and consult the manufacturer for customized solutions.
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**Summary**
Roots blowers can temporarily or simply replace vacuum pumps, but if stable high vacuum is required, it is recommended to choose professional vacuum pumps or combination systems. In practical applications, it is necessary to weigh the vacuum degree, gas properties, and cost comprehensively.
