Screw pump technology

Screw pumps have established themselves for vacuum generation in addition to other areas of application. Their design enables the generation of deep vacuum without contaminating processes with oil or abrasion. New advanced screw pump technologies even meet additional requirements such as high chemical resistance and high condensate compatibility for use in laboratories.

Vacuum technology has become an indispensable part of today's research and analysis laboratories. Numerous processes such as filtration, evaporation or drying can only be carried out efficiently and gently with vacuum as an important aid. Specific requirements for vacuum equipment are determined by the application. What does that mean in concrete terms?

The continuous trend towards high product purity and clean process control results in increased demands on applications in the laboratory. In these cases, oil-free and dry pump technologies contribute to contamination-free operation. They do not require operating fluids (e.g. for sealing) that could enter the process. In addition, they improve efficiency and sustainability by eliminating maintenance-related oil changes and emissions, as well as waste oil disposal. For processes involving aggressive gases and vapors, high chemical resistance is also a basic requirement. For these cases, additional chemically resistant pump technologies are required to ensure smooth and durable operation.

Which vacuum pumps meet these two requirements – oil-free operation and chemical resistance? Dry chemistry diaphragm pumps have been established in laboratories since the 1980s. They enable vacuum down to approx. 1 mbar, which is, however, not sufficient for all processes. For even deeper, clean vacuum, there are dry screw vacuum pumps, or screw pumps for short. These are also suitable for process pressures down to the 10^-3 mbar deep fine vacuum range. For a long time, however, the original industrial pumps were not available for laboratory scale or in a particularly chemically resistant design. The solution: Today, newer developments in screw pumps allow the adapted use of this vacuum technology in the laboratory as well.

Dry screw pumps for vacuum generation are already widespread in sectors such as chemistry, pharmaceuticals or semiconductor manufacturing. The absence of oil is a major advantage. In addition, screw pumps are versatile due to the variability in vacuum pressure and wide range of pumping speeds. Depending on the pump model, the vacuum pressure varies between ambient pressure and 10^-3 mbar. This is why screw pumps are available for applications in both rough vacuum (down to 1 mbar) and fine vacuum (down to 10^-3 mbar). In addition, they are suitable as backing pumps for turbomolecular pumps and for other applications with regard to high and ultra-high vacuum technology. The pumping speed of screw pumps ranges from several m³/h to several thousand m³/h, depending on the application.

Screw pumps are also characterized by their low maintenance requirements. The spindles intermesh without contact, which prevents abrasion and wear from occurring in the first place. They also contain no seals in the working chamber that could wear out. In addition, screw pumps do not require any operating fluids such as oil in the working chamber.

In addition, there are other different features, such as the pitch of the spindles, which allows the operating behavior to be adapted to the desired task. If all chambers are the same size, this is referred to as a constant-pitch pump. In variants with variable pitch, the chamber sizes decreases towards the outlet, resulting in compression. Variable-pitch screw pumps do improve thermodynamic properties; there is less heat and noise generation. However, constant-pitch screw pumps have a higher condensate tolerance, which is advantageous for processes involving solvents.