ZJ Roots vacuum pump

Roots vacuum pump (abbreviated as Roots pump) is a rotary variable volume vacuum pump without internal compression. It utilizes two 8-shaped rotors rotating in the pump casing to generate suction and exhaust effects. Its principle is similar to that of a Roots blower. Due to its operation in a low pressure range, the free path of gas molecules is large, and the resistance to gas leakage through small gaps is high. Therefore, it can achieve a high compression ratio and can be used as a booster vacuum pump; But it cannot directly discharge the gas into the atmosphere alone, it needs to be used in series with the preceding vacuum pump, and the extracted gas is discharged into the atmosphere through the preceding vacuum pump.

The characteristics of Roots pump are:
There is a certain gap between the rotor and the pump chamber, and between the rotors, which do not touch each other and do not require oil lubrication.
2. The rotor has good geometric symmetry, which can increase the speed and thus manufacture compact high pumping pumps.
3. The pump has low vibration and large volume during operation, with a volume utilization coefficient of about 0.5.
4. There is no compression phenomenon in the pump chamber like mechanical vacuum pumps, so it does not require an exhaust valve. That's why condensable steam can be extracted.
5. It starts quickly and can reach the maximum vacuum in a short period of time. Low power and low operation and maintenance costs.
6. Roots pumps have a high pumping speed over a wide pressure range (1000Pa~1Pa) and can quickly discharge suddenly released gas, compensating for the shortcomings of diffusion pumps and oil sealed mechanical pumps with low pumping speed at (1000Pa~1Pa). Therefore, it is most suitable for use as a booster pump.

Roots pumps are widely used in the vacuum metallurgy industry for vacuum degassing, vacuum melting, vacuum treatment of molten steel, as well as in space simulation, low-density wind tunnel and other devices for extracting non corrosive gases. It can also be used in production processes such as distillation, evaporation, and drying in industries such as chemical, food, pharmaceutical, and motor manufacturing.
During operation, the extracted gas enters between the rotor and the pump body through the intake port. At this point, a rotor and the pump body separate the gas from the intake port. The separated gas (as shown by the shaded area in the figure) is sent to the exhaust port during the continuous rotation of the rotor. The space is in a closed state, therefore, there is no compression or expansion. But when the peak of the rotor rotates to the edge of the exhaust port, due to the lower pressure in the V section compared to the pressure at the exhaust port, in order to make the pressure uniform in the connected volume, gas will diffuse from the exhaust port to the V area, and its diffusion direction is opposite to the rotation direction of the rotor. When the rotor rotates again, compress the gas at V to the exhaust port and discharge it. At this point, the other side of the rotor is connected to the air inlet, which sucks in gas. As the rotor continues to rotate, the above pumping process is repeated to continuously discharge the incoming gas. This working process is equivalent to the rotor space increasing from a minimum value to a maximum value, and then decreasing from the maximum value to the minimum value. This is the principle of volumetric action of Roots vacuum pump.
When the Roots pump operates under low inlet pressure, due to the high rotor speed, the linear velocity on the rotor surface is close to the thermal motion velocity of molecules. At this time, gas molecules colliding with the rotor are pushed by the rotor to the high-pressure exhaust port and then eliminated by the pre vacuum pump. This is the molecular principle of Roots vacuum pump.

Scope of use
The ZJ series Roots vacuum pump is a rotary variable capacity vacuum pump that requires a front-end pump to be used. It has a high pumping speed over a wide pressure range and is not sensitive to dust and water vapor in the extracted gas. It is widely used in industries such as metallurgy, chemical, food, and electronic coating.