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Air-cooled Roots Vacuum Pump

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The air-cooled Roots vacuum pump uses an external cooler to automatically circulate the gas to cool the rotor and the pump body. The pump can work continuously under high differential pressure without thermal overloading and directly discharge to air. The pump can be used in series with the fore-pump, can also be used alone.

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Air-cooled roots vacuum pump is based on common vacuum pump, with the addition of bypass gas cooling system. The external cooler make the gas auto recycling to cool down the rotor and casing, and the cooled gas flows into suction cavity from casing two sides, this will avoid overheating of the casing caused by gas compression and make reliable, enduring operation in high differential pressure and high compression ratio, with no influence on pump performance. The pump can be used single or in multi series, or combine with liquid ring pump or common roots pump into units to get high vacuum for various process.

Two rotors (two blades or more) in the pump chamber are installed on a pair of parallel shaft, and driven by two wheel gears with 1:1 transmission ratio and make opposite rotation. The two rotors, rotors and inner surface of the casing remain a certain gap, which can achieve high speed operation. Different with common roots pumps, the air-cooled roots vacuum pump are designed with a reflux port on the side of the casing,which used to introduce the cooled gas into pump chamber to cool down rotors, so the rotors’ temperature will be kept within specified range, therefor, the air-cooled roots vacuum pumps can withstand higher differential pressure (as high as 90kPa) without overheating, and the single pump can achieves an ultimate pressure of approximately 130 hPa.


  1. Used alone or in series, or connected with liquid ring pumps
  2. Discharged directly without any waste water;
  3. Work under high pressure, can appropriately reduce the fore pump to achieve energy-saving effect;
  4. Effectively solved the problem of overloading and overheating which caused by the D/P of the common roots vacuum pump and the different vacuum degree of fore-pump.
  5. The dynamic seal of the spindle transmission torque is static seal (ie no skeleton oil seal and mechanical seal), realize Zero-leakage transmission of power.
  6. No mechanical contact friction noise, avoid high frequency vibration to transmit power to realize the smooth operation of roots vacuum pump.
  7. Compared with rigid coupling, there is no impact when starting, and it is convenient for installation, disassembly, debugging and maintenance.
  8. Isolation sleeve static seal instead of rotating shaft motive seal which can thoroughly eliminate the vacuum problems such as vacuum leakage and oil leakage due to shaft seal wear and achieve long-term sealing.
  9. No lubrication, no media and lubricant pollution, purification environment.
  10. Sealing performance is independent of shaft speed.
Model Max. speed
Ultimate pressure
Rotate speed
Inlet port diameter
Motor power
ZJQ-30 30 2 x 104 3000 63 0.75~5.5
ZJQ-70 70 2 x 104 3000 80 1.1~11
ZJQ-150 150 1.6 x 104 3000 100 3~15
ZJQ-300 300 1.6 x 104 1500 160 4~30
ZJQ-600 600 1.6 x 104 1500 200 7.5~55
ZJQ-1200 1200 1.6 x 104 1500 250 11~132
ZJQ-1800 1800 1.3 x 104 1500 320 15~200
ZJQ-2500 2500 1.3 x 104 1000 400 18.5~250
ZJQ-3750 3750 1.3 x 104 1500 400 30~355
ZJQ-5000 5000 1.3 x 104 1000 500 45~375
ZJQ-12000 12000 1000 500 75~280

Working principle


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