Dry Screw Vacuum Pumps, Oil-Free Compression

S-Series by Elmo Rietschle

Dry Screw Vacuum Pumps | S-Series

The S-Series by Elmo Rietschle features advanced, high-efficiency dry screw vacuum pumps that set the standard for durability and performance in industrial vacuum applications. Screw vacuum pumps are renowned for their efficiency, reliability, and oil-free operation which makes them suitable for a wide range of industries including food and beverage, pharmaceuticals, packaging, and more. 


The S-Series includes various models of rotary screw type vacuum pumps with different capacities and features to meet specific application requirements, providing you with a versatile and high-performance vacuum solution.



Screw Pump Features and Advantages 

Dry and contact-free, screw vacuum pumps require no lubrication in the pumping chamber. This translates into major advantages: no process contamination and no pollution caused by the pump operation. 

Dry screw pumps in the S-Series are designed with high vapor and liquid tolerance, are easy to service, and have a long service life. 

  • Dry running, contact-less operation

  • High vacuum in one stage

  • Application specific options

  • High water vapor tolerance

  • Short evacuation time due to high suction capacities

  • Low noise level

  • Easy to service



Types of Dry Running Rotary Screw Vacuum Pumps 

VSI Twister

Capacities from 71 to 212 cfm, maximum end vacuum 29.917 inHg (0.075 Torr). Continuous variable pitch screws ensure the highest efficiency of operation and energy consumption. Progressive graduation of the screw pitch and maximum sealing thanks to labyrinth, shaft and piston ring seals.

Sealing gas is optional; benefits include low noise, low operating temperatures and can be easily serviced. Designed for industrial applications devoid of aggressive gasses. General industrial applications such as packaging, drying and coating or vacuum furnaces are best served by our VSI range of pumps.



VSB Chemical Duty – Capabilities on this pump range from 70 – 440 CFM, getting down to an ultimate vacuum of .020 Torr. The standard pump includes top of the line Kalrez O-rings. Heavy duty Niflon coating comes standard on all vacuum surfaces, lengthening the lifespan of the pump when dealing with chemically abrasive products and aggressive pumping speeds.

Performance and Technical Specifications

In the pump housing, two parallel screw rotors, both timing gear synchronized, turn in opposite directions. Gearbox and mechanical seals are oil lubricated. Cooling is achieved through the continuous flow of coolant through the pump housing.
The S-Series are screw pumps designed with high vapor and liquid tolerance, are easy to service and have a long service life and the low rotational speed ensures low noise and low vibration.

Our VSI screw vacuum pump systems achieve an ultimate vacuum of 29.917 inHgV (0.075 Torr) and can operate at any pressure between maximum vacuum and atmospheric pressure. Capacities of 70 and 212 cfm are available.

Common Applications and Industries for Screw Vacuum Pumps 

Dry screw vacuum pumps are a reliable solution where clean, oil free vacuum is required. Screw pumps can also be combined with a vacuum booster in customized vacuum systems to achieve high suction capacities and vacuum levels. 

Common applications for screw type vacuum pumps include: 

  • Bottling

  • Packaging Industry

  • R&D / Laboratories

  • Solar Technology

  • Surface Technology / Electronics

  • Industrial applications including Cleaning, Coating, Drying, Dust Extraction Systems, Industrial Furnaces, Vacuum Metallurgy

Dry Screw Vacuum Pumps - How They Work

A screw vacuum pump consists of two parallel, screw-shaped rotors, one with a right-hand thread and the other with a left-hand thread. Both screws turn in the compression housing without friction and at very tight clearances. They are synchronized via a precision gear. The compression housing and the special shape of the screws form the compression chambers. 
Due to the opposite rotation of both screws the chamber connected with the suction port is enlarged and the gas is transported into the compression chamber. Then the chamber moves axially from the suction side to the pressure side. 

In variable pitch models, the gas is compressed throughout the length of the screw due to the constant variable pitch design, resulting in greater efficiency. On the pressure side the chamber is moved against the axial housing wall and the volume is reduced until the front surface of the screw opens the pressure channel and the pre-compressed gas is discharged through the pressure connection. Cooling is achieved using a water cooled outer chamber.