More Efficiency And Performance With Pfeiffer Vacuum Screw Pumps

With the screw pumps from Pfeiffer Vacuum you get modern vacuum pumps for industry that have been developed for high vapor and particle compatibility. Our pump supplies your process with almost constant pumping speed.

Dry and robust screw pumps

Due to their wide range of pumping speeds, the series of HeptaDry dry screw pumps is ideal for applications in both rough and fine vacuum in industry. It can be used for a variety of industrial applications such as freeze drying, metallurgy and coating. HeptaDry is the ideal solution for areas where an oil-free vacuum is required. The pumping speed of this product range ranges from 100 to 630 m3/h.

The one-piece rotors with variable pitch are a particular advantage. They ensure the necessary internal compression of the HeptaDry pumps. In addition, the variable pitch of the screw rotors results in lower power consumption compared to constant pitch screw rotors as well as low cooling water consumption, making the vacuum pump an economical solution. The innovative design and low speed of the pumps ensure low stress on the bearings and seals.

Our screw pumps from the HeptaDry series are ideal for use as individual pumps or in combination with our HiLobe Roots pumps in various areas of application.

Brochure: HeptaDry

Screw pump in two different versions

The HeptaDry is available in two different versions in order to offer the right solution for as many applications as possible.
The two options differ in terms of accessories, motors, inlet and outlet, and much more. They can each be configured as required in consultation with our experts.

Hepta L – The basic version for light processes

Hepta L

Hepta P – The configurable process version

Hepta P

Areas of application for screw pumps

The applications of screw pumps in vacuum are diverse. Factors such as process compatibility and pumping speed determine whether a screw pump is suitable for a particular vacuum application. Thanks to their robustness and range of pumping speeds, screw pumps are used in drying, coating or chemistry. But the HeptaDry has also proven itself in the areas of electron beam welding and metallurgy.

HeptaDry screw pumps are well suited for chemical applications, processes with dust e.g., in crystal growing, processes with heavy condensation or as a backing pump in applications in the high and ultra-high vacuum range. Professional advice from our experts can help ensure the right screw pump is chosen for your vacuum needs.

Functional principle of screw pumps

In the classification of vacuum pumps, screw pumps belong to the group of positive displacement vacuum pumps and therefore work according to the rotating displacement principle like, for example, Roots pumps. In the HeptaDry screw pumps, two rotors rotate inside the pump and thus pump the gas. Because of their appearance, these rotors are also called screws. The two parallel, interlocking screw rotors with opposing threads rotate in opposite directions synchronously without touching each other in a cylindrical, tightly enclosing housing. This arrangement forms a multi-stage pump. Due to the mutual engagement of the two rotors, closed volumes in each thread are transported along the rotors to the outlet.

The resulting volume flow heats the pump, so it must be tempered with coolant to keep the gap dimensions from decreasing. The volume flow also generates a high power loss. This power loss of the pump can be reduced through the internal compression, which is achieved by reducing the thread pitch towards the outlet. The gap between the housing and the rotors, and between the rotors themselves, ultimately determines the final pressure that can be achieved by a screw pump. The geometry and the resulting gap shape at the profile engagement between the rotors also have a major influence on the final pressure. As a general rule, the dimensions of the pump increase with the desired pumping speed.

HeptaDry 3D video

HeptaDry - the dry screw pump - 3D

By configuring it appropriately for the application, the vacuum pump can be optimally aligned to its area of application. Sealing gas and gas ballast are most commonly used. As with other vacuum pumps, defined gas can be introduced into the high-pressure stage of the pump via a gas ballast valve to counteract condensate formation within the pump or to remove it from the operating fluid. Condensate increases the final pressure and leads to corrosion, which in the worst case can result in pump failure. The sealing gas is also used to prevent condensation. It is used to prevent severe dilution of the lubricants when conveying reactive gases by feeding inert gas into the working and gearbox space.

There are also purge gas, various seals (labyrinth, oil-lubricated mechanical seals, gas-lubricated mechanical seals and lip seals) and various motor configurations.

Maintenance of screw pumps

In addition to extending its service life, regular maintenance of a screw pump ensures that the pump can be used effectively and reliably in the process and that it delivers the desired performance even after a long period of use:


Dust separators (SAS) can be mounted on the inlet side, which protect the pump from particles from the process. Different versions are available depending on the pump's connection flange. A silencer can be added to the exhaust side to reduce the noise level. In addition, on some models it is possible to provide a check valve between this and the pump, which serves to protect the vacuum pump from returning condensate and particles. The temperature of the motor winding can be monitored and the motor can be protected using a PTC tripping device.

The accessories, in addition to the configuration tailored to your application, can lead to increased safety and service life if used correctly. Our experts are also happy to answer any questions you may have about accessories.