**Detailed explanation of the difference between Roots blower and rotary blower**
Roots blower and rotary blower are both positive displacement fans, but they have significant differences in structure, working principle, performance, and application. Here is the core comparison between the two:
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**1、 Comparison Table of Core Differences**
|* * Comparison item * * | * Roots blower * * | * Rotary blower (such as screw type, slide type) * *|
|------------------|----------------------------------|----------------------------------------|
|* * Working principle * * | Dual rotor meshing conveying gas (without internal compression) | Single/multi rotor rotating compression gas (with internal compression)|
|* * Compression method * * | No internal compression, pressure is generated by system resistance | Internal compression (such as screw engagement, slide sliding compression)|
|* * Structural Features * * | Dual rotor+synchronous gear, fixed clearance | Single rotor or screw, dynamic sealing|
|* * Efficiency * * | Low (high energy consumption at high pressure) | High (internal compression reduces energy loss)|
|* * Noise * * | Large (high-frequency pulsating noise) | Low (continuous compression, smooth airflow)|
|* * Maintenance cost * * | Low (simple structure, adjustable gap) | High (precision seals need to be replaced regularly)|
|* * Pressure range * * | Single stage ≤ 0.5 bar, double stage ≤ 1.0 bar | 0.5~3 bar (screw type can reach higher)|
|* * Typical Applications * * | Sewage Treatment, Pneumatic Conveying, Vacuum Adsorption | Compressed Air, Vacuum Systems, Chemical Processes|
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**2、 Differences in working principles**
**1. Roots blower**
-* * Working process * *:
1. Two rotors (two or three blades) rotate in opposite directions through synchronous gears.
2. Gas is drawn in from the inlet and enclosed in the chamber formed by the rotor and the housing.
3. The gas is forcibly pushed to the exhaust port, and the pressure is determined by the system resistance (without internal compression).
-* * Features * *:
-The flow rate is constant and proportional to the rotational speed.
-Reverse rotation can cause rotor collision damage.
**2. Rotary fan (taking screw type as an example)**
-* * Working process * *:
1. The yin-yang screw meshes and rotates, gradually compressing the gas in the spiral groove.
2. The gas volume decreases and the pressure increases (* * internal compression * *).
3. The compressed gas is discharged from the exhaust port.
-* * Features * *:
-The pressure is determined by the geometric shape of the screw, resulting in higher efficiency.
-Lubricating oil cooling and sealing are required (except for oil-free screws).
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**3、 Performance comparison**
|* * Parameters * * | * Roots blower * * | * * Rotary blower * *|
|------------------|-------------------------------|-----------------------------|
|* * Flow range * * | 0.5~300 m3/min | 1~500 m3/min|
|* * Energy efficiency ratio * * | 50~70 (applicable for low voltage) | 70~85 (better for medium and high voltage)|
|* * Noise (dB) * * | 75~90 (requires muffler) | 60~75 (quieter operation)|
|* * Temperature rise * * | High (no internal cooling) | Low (oil or air cooling design)|
|* * Applicable medium * * | Clean or dusty gas | Can handle gases containing liquid droplets and fine dust|
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**4、 Selection suggestions**
**Priority selection of Roots blower**
-Low pressure constant flow rate (such as sewage treatment aeration, powder transportation).
-* * Stain resistant environment * * (simple structure, not easily clogged).
-* * Limited budget * * (low initial and maintenance costs).
**Priority should be given to selecting a rotary fan**
-Medium to high voltage demand (such as compressed air stations, vacuum packaging).
-Low noise requirements (such as hospitals and laboratories).
-Energy saving scenario (with higher long-term operational efficiency).
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**5、 Common Misconceptions**
1. * * "Rotary fan=Roots blower"**
-Error: Roots blower is a type of rotary blower, but rotary blowers also include screw type, slide type, etc.
2. * * "Roots blower can compress gas"**
-Error: Roots blower only delivers gas, pressure is generated by system resistance.
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**6、 Maintenance comparison**
|* * Maintenance item * * | * Roots blower * * | * * Rotary blower * *|
|------------------|-------------------------------|-----------------------------|
|* * Daily maintenance * * | Check gear oil and rotor clearance | Replace lubricating oil and filter element|
|* * Vulnerable parts * * | Synchronous gears, bearings | Screw coatings, shaft seals|
|* * Overhaul cycle * * | 3-5 years (gap adjustment) | 2-3 years (seal replacement)|
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**Summary**
-Roots blower: simple structure, dirt resistance, suitable for low-pressure constant flow, but with high noise and low energy efficiency.
-Rotary fan: energy-saving, low-noise, suitable for medium and high pressure, but high cost and complex maintenance.
Select the appropriate type based on pressure requirements, medium characteristics, and budget. If specific selection suggestions are needed, further analysis of operating parameters can be provided!
