Technical parameters of molecular pump
Molecular pump is a kind of vacuum pump which uses high-speed rotating rotor to transfer momentum to gas molecule, so as to obtain directional speed, and then compressed and driven to the exhaust port for the front stage pumping. Molecular pumps cover almost all possible applications, with a unique electromechanical design, high front-end pressure resistance, suitable for 10-10-10 MB vacuum environment.
Technical parameters of molecular pump:
| Model | unit | FB-300 | FB-650 | FB-1300 | FB-2000 | |||||
| High vacuum flange | mm | 100CF | 100ISO | 150CF | 160ISO-K | 200CF | 200ISO-K | 250CF | 250ISO-K | |
| Fore pipe flange | mm | 25KF | 40 KF | 40 KF | 50 KF | |||||
| Pumping speed | L/s | 300 | 650 | 1300 | 1800 / 2000 | |||||
| Compression ration | N2 | >108 | >109 | >109 | >108 | |||||
| H2 | >1×103 | >8×103 | >1×104 | >1×104 | ||||||
| Ultimate pressure | Torr | >3×10-7 | >2×10-6 | <8×10-8 | <5×10-7 | <8×10-8 | <5×10-8 | <8×10-8 | <5×10-8 | |
| Rotary Speed | rpm | 30000 | 24000 | 24000 | 24000 | |||||
| Bearing | / | Grease lubricated ceramic bearing | ||||||||
| Start-up time | min | <4 | <5 | <5 | <5 | |||||
| Fore pump speed | L/s | 2 | 4-8 | 8-15 | 8-15 | |||||
| Cooling | / | Air | Water | Water/air | Water/air | |||||
| Cooling water | Temp. | ℃ | / | ≤20 | ≤20 | ≤20 | ||||
| Consum. | L/min | / | 1 | 1 | 1 | |||||
| Mounting position | / | Any | Any | Any | Any | |||||
| Weight | Kg | 11 | 22 | 27 | 35 | |||||
The advantages of molecular pumps are:
1. no oil vapor pollution, can get a clean high vacuum.
2. start fast, activate fast.
3. Turbomolecular pumps are mostly small space, installation direction is not restricted (except oil-lubricated bearings), can be used in the installation of restricted locations.
4. gas transport capacity is strong, suitable for high gas loading process, such as sputtering, etching and so on.
5. The inlet pressure range can be operated between 10x-1 and 10x-3 Torr. In this pressure range, the ion pump can not be used. For cryogenic pumps, throttling pumping speed or frequent regeneration are required, and the work of the diffusion pump will become unstable.
Disadvantages of molecular pumps:
1. high price
2. sensitive to particulate matter or sediment.
3. some pumps are resistant to atmospheric impact, and the blades will be damaged due to bending and bending.
Matters needing attention in operation of turbine molecular pump:
1. Turbomolecular pump can not be shut down when the front-stage pump is working (the front-stage pipeline is connected) and the vacuum chamber is in a vacuum state. Otherwise, oil vapor will quickly flow back from the front-stage pipeline to the clean end of the pump.
2. Molecular pump system must shut down the cooling water of the molecular pump before stopping the drying gas, and it should be inflated from the high vacuum end of the pump. Never inflate the front line of the pump.
3. Standards for selecting the system’s front-stage pumps: the inlet end of the turbomolecular pump should be kept in the state of molecular flow.
4. do not allow turbo molecular pumps to operate at a lower than rated operating speed.
5. Molecular pump inlet should be equipped with protective mesh to avoid foreign bodies into the pump to damage the pump rotor and stator blades.
Compared with oil seal rotary vane pump and turbine dry pump, molecular pump has cleaner working environment and can achieve extremely high vacuum. However, the molecular pump can not work at atmospheric pressure, must be able to work at atmospheric pressure and other rough vacuum pumps (oil seal rotary vane pump or turbine dry pump) combined use. Molecular pumps are complex in structure and expensive in price. Vibration will occur when rotating at high speed.
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