1. Combined type (Roots vacuum pump + Claw vacuum pump)
The combined type (Roots+claw) screw vacuum pump is classified as Roots to develop the vacuum thermal efficiency under lower water pressure, and the claw to develop the vacuum thermal efficiency under higher water pressure.
Its basic concept is the same as that of the vapor loop and the circular lobed classification. There are also some that change the final stage of the screw vacuum pump to a star-shaped classification, so that the vapor can be divided into five parts during the entire rotation, just like the three-circle split-type classification can be divided into three parts
2. Internal compact screw type
The continuous reduction of the capacity between the screw rods promotes the internal tightening of the screw vacuum pump. In many processes, this type of internal shrinkage is the same as a multi-stage centrifugal pump, which simply causes the physical transformation of the vapor in the screw vacuum pump to cause dryness or vaporization.
3. double round lobe type
The multi-stage classification of double-circle lobes promotes the vapor loop to be equivalent to chaos, and each stage requires a large amount of hydrogen to be mixed with water and isolated. In order to achieve a good vacuum, there are very strict regulations on each gap. This type of classification results in lower power consumption of screw vacuum pumps due to the increased internal shrinkage ratio.
4. three round lobes
The mechanism of the three-circle-lobe classification is the same as that of the method described. The vapor is divided into three parts only during the entire rotation, instead of being divided into two parts like the double-circle-lobe classification. In order to further reduce the power consumption, some of the gearboxes will use two DC motors, but this will also reduce the torque and reduce the potential for restart.
5. External compact screw type
In the classification of the external compact screw type, two equidistant screw rods are used. This promotes the reduction of the internal tightening of the screw vacuum pump and the simplicity of the vapor loop. In that way, the time that the vapor stays in the screw vacuum pump body is also short. This type of classification shows very strong reliability in the chaotic optoelectronic device process.