The suction (negative pressure capacity) of a Roots blower depends on its design and operating conditions, and is usually represented by * * vacuum degree (negative pressure value) * *. Here is a detailed analysis:
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**1、 The suction range of Roots blower**
1. * * Standard Roots blower**
-Vacuum degree: -9.8kPa to -49kPa (approximately -0.1kgf/cm2 to -0.5kgf/cm2).
-* * Typical Applications * *:
-Mild suction (such as vacuum packaging, material conveying).
-It needs to be used in conjunction with a vacuum pump to achieve higher negative pressure.
2. * * Specialized vacuum Roots blower * * (improved high-pressure type)
-Vacuum degree: -58.8kPa to -98kPa (approximately -0.6kgf/cm2 to -1.0kgf/cm2).
-* * Features * *:
-Strengthen the sealing structure to reduce internal leakage.
-It needs to be paired with a front-end pump (such as a rotary vane pump) to form a vacuum unit.
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**2、 Key factors affecting suction**
|* * Factor * * | * * Explanation * *|
|------------------|-------------------------------------------------------------------------|
|Speed * * | The higher the speed, the faster the pumping speed, but the increase in vacuum degree is limited (limited by volumetric efficiency). |
|Sealing performance: The smaller the impeller clearance, the higher the vacuum degree (special vacuum type clearance ≤ 0.1mm). |
|* * System leakage * * | Leakage of pipes or valves can significantly reduce the vacuum level. |
|Gas properties: Extracting high-temperature or corrosive gases can reduce efficiency and limit vacuum. |
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**3、 Example of suction calculation**
-* * Formula * *:
\[
\Text {actual vacuum degree}=\ text {theoretical vacuum degree} \ times \ text {volumetric efficiency} \, (usually 70 \ \ sim90 \)
\]
case
A Roots blower with a nominal -49kPa and a volumetric efficiency of 80 can actually achieve:
\[
-49\text{kPa} \times 0.8 = -39.2\text{kPa}
\]
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**4、 Roots blower vs other vacuum equipment**
|* * Equipment type * * | * * Vacuum degree range * * | * * Features * * | * * Applicable scenarios * *|
|------------------|--------------------|-------------------------------------|-------------------------|
|Roots blower * * | -9.8~-98kPa | High flow, medium low vacuum, requiring a front-end pump | Material conveying, coarse vacuum|
|* * Rotary vane vacuum pump * * | -90~-100kPa | High vacuum but low flow rate | Laboratory and precision equipment|
|* * Water ring vacuum pump * * | -70~-95kPa | Corrosion resistant, capable of extracting moisture | Chemical and papermaking industries|
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**5、 Methods to increase suction power**
1. * * Series connected front-end pump**
-The combination of Roots blower and rotary vane pump can reach * * -95kPa * * or above.
2. * * Optimize sealing**
-Use mechanical seals or labyrinth seals to reduce gas reflux.
3. * * Reduce system leakage**
-Check the pipeline interface and use vacuum specific valves.
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**6、 Selection suggestions**
-* * Ordinary suction requirements * * (such as packaging and transportation): Choose the standard type (-20~-49kPa).
-Industrial vacuum requirements (such as drying and degassing): Choose a vacuum unit (Roots+rotary vane pump).
-Corrosive gas: requires stainless steel material and anti-corrosion coating.
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**7、 Precautions**
1. * * Strictly prohibit dry running * *: Before vacuuming, ensure that there is gas flow at the inlet to avoid overheating and damage.
2. Overload protection: Monitor current during high vacuum operation to prevent motor burnout.
3. * * Maintenance cycle * *:
-Check the gear oil monthly;
-Clean the intake filter quarterly.
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**Summary: The suction capacity of a Roots blower is usually ≤ -49kPa. If a higher vacuum degree is required, it must be used in conjunction with a front-end pump! When selecting, it is necessary to clarify the requirements for flow rate, vacuum degree, and medium.
