The major advantages of screw pumps and hydropower screws are:

• high flow rates;
• high efficiency;
• high reliability;
• low maintenance;
• long service life (little wear);
• fish-friendly and easy to apply in natural streams (thanks to the atmospheric operating principle and the relatively low nominal speed);
• self-priming;
• easily accessible;
• ability to run dry for long periods of time.

At Vandezande, a screw pump unit consists of the following main components:

Screw pump body
The screw pump body consists of a central tube or beam on which blades are welded to form a continuous spiral thread.  Depending on the flow required, a double or multiple-bladed spiral is used.

Screw pump trough
In addition to the custom-made concrete trough for the screw pump installed, it is also possible to choose either a steel trough mounted together with the screw in a rectangular concrete trough, or a self-supporting prefabricated steel unit which is provided with the necessary supports.  With this latter option, the screw pump is supplied with trough and drive line as one unit.

Splash guards
The purpose of this attachment is to minimize leakage by increasing the filling rate of the screw pump and the efficiency accordingly.

Upper bearings
The grease-lubricated upper bearings absorb both axial and radial forces.  The bearing housing is either wall-mounted or floor-mounted. The axial and radial bearings have an automatic adjustment so that angular deformations caused by the deflection of the screw can be absorbed.

Lower bearings
The self-adjusting lower bearings only absorb radial forces and allow for thermal expansion of the screw.  The lower bearings are mounted in a cast-iron housing with an alloy specially designed for this application.  Different types of lower bearings are available: with grease lubrication, oil lubrication or without lubrication (ecological bearings).

Drive unit
The driving unit consists of an asynchronous motor connected to the fast-rotating shaft of a helical or parallel gearbox through a belt transmission or elastic coupling.  The low-speed shaft of the gearbox is connected to the screw pump shaft by means of an elastic coupling.  Screw pumps are provided with a backstop brake in the gearbox.  Hydropower screws are provided with an external brake fitted on the fast-rotating shaft of the gearbox.