Advantages and disadvantages of screw vacuum pumps and claw vacuum pumps

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The main types of dry, oil-free vacuum pumps currently available in the domestic market are screw vacuum pumps, reciprocating vacuum pumps, and claw vacuum pumps. Since reciprocating vacuum pumps generally achieve lower levels of vacuum, no further comparison will be made for them here. A screw vacuum pump is a pumping device that utilizes a pair of screws rotating synchronously at high speed in opposite directions within the pump casing to create suction and exhaust action. It features a high vacuum level, relatively stable performance, and simpler assembly and maintenance. The general vacuum level is around 1 Pa, which is the ultimate vacuum. For claw-type vacuum pumps, they are variable-volume dry vacuum pumps whose rotors have a claw-shaped design. In the case of pumps with 4 pumping chambers, the vacuum level achieved is generally around 50 Pa, which represents the limit vacuum level. Moreover, the gaps between the components are kept very small. As a result, gas flow becomes poor as it passes through each pumping chamber one after another. When the gaps are small, and products made from materials such as Hastelloy or double-layer stainless steel are used, as stated by manufacturers, the material may deform when the temperature rises, leading to friction and seizure between the rotor and the pumping chambers. This problem usually occurs after 1–3 months of use by customers, given that stainless steel has a high heat capacity and slows down heat dissipation. Moreover, maintenance and repair are rather troublesome; generally, it is not possible to disassemble or assemble it at the customer’s site.