Screw pumps are utilized to draining low laying areas, such as the polders of Northwest Europe. A so called Archimedes’ (or Archimedean) screw pump consists of a long worm wheel that is diagonally placed in a pipe or trough, and creates upward displacement of water when driven. These Archimedes screws have been in use for many centuries as applications are found in irrigation and draining purposes.
The fish friendly screw pump explained
In conventional screw pumps the first winding scoops water from the polder that is lifted to the downstream waters by the subsequent windings. Migrating fishes have the possibility to pass through the displaced water to find their way out of the polder, but approximately 15% of all fish that utilise this transport route suffer some kind of damage while passing a conventional screw pump. The premium cause for damage is that a number of fish is hit by the first winding when it hits the water. A secondary cause is that fish get stuck between the screw and the trough in which the screw is placed.
Adjustments to the design of conventional screw pumps have resulted in a design that does not inflict any damage on passing fish. In the FishFlow screw pump the blades do not stretch across the full width up to the tip of the screw, instead the width of the blades gradually decreases from the middle outwards during the last few windings. The second adaptation concerns the housing of the screw. In the FishFlow screw pump, the screw is enclosed in a pipe that is attached to the screw and thus rotates together with it.
These adaptations make damage to passing fish through hits of the first winding and damage following entrapment impossible and make the screw pump into a fish friendly facility for downstream migration.
- 100% fish friendly.
- High efficient pump (high volume and no leakage).
- Very silent.
- Patented design.
- Very long life expectancy.
- Low maintenance.
- Impervious for obstructions.
- Cost saving on civil works.
- Optionally adjustable for following fluctuating water levels.
- Option to function as fish friendly turbine.
- Triple helix in fibre glass reinforced composite.
- Screw diameter from 0.6 to 5.0 metres.
- Low-maintenance bearings.
- Electric motor driven.
- Variable frequency drive for optimal efficiency.
Our enclosed Archimedes’ screw pump demonstration model shows how gentle and smooth our screw pumps operate and what is meant by pumping against the level:
The start up and stop of one of the Ø 2.5 m screw pumps at Thorne Moors. When an enclosed screw pump is stopped, it counter-rotates a few times to let it run dry, and it is emptied of water and fish.
To illustrate, a video of a conventional, open screw: