Stainless steel screw vacuum pump is a type of dry positive displacement vacuum pump, which rotates in the pump chamber through a pair of precision meshing screw rotors to achieve gas suction, compression, and discharge. The following is a detailed analysis of its working principle:
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**1、 Core working principle**
1. * * Rotor motion**
-* * Master slave rotor * *: A pair of stainless steel (usually 304/316L material) spiral screws, designed with asymmetric double or multiple heads, synchronously rotating in the opposite direction through high-precision gears.
-Non contact meshing: Maintain a gap of 0.1-0.3mm between rotors to avoid metal friction (no lubrication required).
2. * * Working process**
-* * Inhalation stage * *: Gas enters the closed chamber formed by the rotor and pump casing from the intake port (Figure ①).
-Compression stage: The rotation of the rotor gradually reduces the volume of the chamber, and the gas is pushed axially and compressed (Figure ② → ③).
-Exhaust stage: Compressed gas is discharged from the exhaust port (Figure ④).
```plaintext
[Schematic diagram of work cycle]
① Inhalation → ② Closure → ③ Compression → ④ Exhaust
```
3. * * Dry operation**
-No oil/water involvement throughout the process, suitable for clean working conditions such as medicine and food.
-Relying on rotor clearance and surface coating (such as PTFE) to achieve sealing.
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**2、 Key structural components**
|* * Components * * | * * Functions * * | * Advantages of Stainless Steel * *|
|-------------------|-------------------------------------------------------------------------|----------------------------------|
|* * Screw rotor * * | Gas compression core, requiring dynamic balance correction | Corrosion and high temperature resistance (up to 300 ℃)|
|* * Pump casing * * | Forming a closed chamber with cooling jacket (water-cooled/air-cooled) | Resistant to chemical media erosion|
|* * Synchronous gear * * | Ensure rotor meshing (ISO grade 4 accuracy) | Surface chrome plated for rust prevention|
|* * Bearing assembly * * | Bearing for axial/radial forces (commonly used angular contact ball bearings) | 316L material suitable for harsh environments|
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**3、 Performance characteristics**
1. Vacuum range**
-Ultimate vacuum: 0.1~10 Pa (can reach 102 Pa with Roots pump).
-* * Work pressure * *: atmospheric pressure~0.1 Pa (single-stage), multi-stage series expandable.
2. * * Traffic characteristics**
-Flow range: 5-2000 m3/h (positively correlated with rotor diameter and speed).
-Constant flow output (volumetric characteristic).
3. * * Advantage Comparison**
-* * vs rotary vane pump * *: No oil pollution, maintenance cost is 50% lower.
-* * vs Roots pump * *: Single stage compression ratio (up to 10:1), no need for a front stage pump.
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**4、 Typical application scenarios**
|* * Industry * * | * * Purpose * * | * * Special Requirements * *|
|------------------|----------------------------------|----------------------------------|
|* * Pharmaceutical * * | Freeze drying machine, sterile packaging | FDA certification required (material 316L+electrolytic polishing)|
|Chemical industry * * | Solvent recovery, vacuum distillation | Explosion proof design (Ex d Ⅱ BT4)|
|* * Electronics * * | Semiconductor coating, LED packaging | Extreme vacuum ≤ 1 Pa, vibration<1.5 μ m|
|* * Food * * | Vacuum packaging, dehydration drying | Compliant with NSF lubricant standards|
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**5、 Workflow Example (Taking Pharmaceutical Freeze Drying as an Example)**
1. * * Evacuation stage * *: Within 30 minutes, pump from atmospheric pressure to 10 Pa (remove air and moisture).
2. * * Maintenance stage * *: Stabilize at 1-5 Pa for 48 hours (sublimation drying).
3. * * Breaking stage * *: Inject sterile nitrogen gas to restore normal pressure.
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**6、 Maintenance points**
1. * * Daily inspection**
-Rotor clearance (measured monthly, adjusted for wear>0.05mm).
-Gearbox oil level (replace synthetic oil every 2000 hours).
2. * * Deep maintenance**
-Inspect the rotor coating annually (if the peeling area is greater than 5, it needs to be repainted).
-The bearing life is usually 20000 hours (replaced when the vibration value is greater than 4.5mm/s).
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**7、 Troubleshooting Guide**
|* * Fault phenomenon * * | * * Possible cause * * | * * Solution * *|
|------------------|------------------------------|----------------------------------|
|Vacuum degree decrease | rotor coating wear/system leakage | helium leak detection+coating repair|
|Abnormal vibration | Bearing damage/rotor dynamic balance failure | Replace bearings+re calibrate dynamic balance|
|Overheating (>90 ℃) | Blockage of cooling system/high compression ratio | Clean cooling channel+check exhaust back pressure|
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**Tip: When selecting, attention should be paid to the gas composition (corrosive gases require special rotors) and particulate matter content (>5 μ m requires a pre filter). Although stainless steel screw pumps are expensive (30-50% more expensive than cast iron), their lifespan can reach more than 10 years.
