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Archimedean Screw Pumps
The (Archimedean) Screw Pumps are well-known for their excellent qualities such as the Simple & Rugged design, the high efficiency, the capacity to pump raw water(even when it contains an amount of solids and debris) and their lifetime reliability. Spaans Babcock has a worldwide reputation of being the oldest and the largest manufacturer of Archimedean Screw Pumps with a track-record of more than 30,000 screw pumps installed. Screw Pumps can be used for capacities from 15 litres/sec up to max 11 m3/sec and come in 3 basic forms: built in the traditional concrete trough, with steel trough liner and the prefabricated, ‘ready to install’ compact units. To learn more about the qualities and advantages of screw pumps please select from the menu on the left or simply contact us!
Screw Pump in a Concrete Trough
The classic and most common form is the arrangement of the screw pump in an open concrete trough where the screw, suspended between the upper- and lower bearing, rotates free from the trough with a minimal gap of only a few millimetres.
In order to achieve the perfect trough that is just a few millimetres larger in diameter than the screw pump, the trough is formed (screeded) with the help of the slow rotating screw itself which has been temporarily provided with a screed-strip; while soft concrete is poured in the trough, the rotation of the screw forms a perfect ‘imprint’ of the screw.
Spaans Babcock has several experienced supervisors available to assist with installation and screeding anywhere in the world.
Screw Pump with a Steel Trough Liner
Although this type requires a similar civil construction as the previous described ‘concrete trough’, there is however no screeding to be done!; instead a prefabricated steel trough liner is backfilled with concrete. Spaans Babcock prefabricates the trough (either in steel or stainless steel) at the exact diameter and ships it together with the pump.
The steel trough liner increases the wear resistance of the trough in situations where lots of stones and pebbles come to the inlet.
Compact Screw Pump (ESP: Encased Screw Pump)
For this type there is no civil construction required! A prefabricated self-supporting steel construction with integrated inlet-section, outlet-section, trough, screw pump and drive unit is preassambled in our factory and shipped in one piece, ready for immediate installation. The only civil requirement is a support in the inlet channel and a support on the outlet channel. The compact screw pump is ideal for small capacities but is also applied for capacities up to 5 m3/sec.
The excellent qualities of Archimedean Screw Pumps make them ideally suitable for:
STP's: Sewage Inlet Pumps
On most STP’s gravity propels the raw sewage below ground level to the plant. The use of Archimedean screw pumps makes it possible to lift large quantities of sewage to a higher level without the need of installing a screen upstream below ground level.
Storm Water Pumping Stations are often waiting in stand-by mode (for 80% of the year) but when heavy rainfall suddenly strikes, they must be immediately ready to start pumping thousands of cubic meters of polluted rainwater containing lots of debris. The storm water pumps must not get blocked during these critical hours! The Archimedes screw pump is the only type of pump that can offer this reliability.
The typical problem of drainage pumping stations is the fluctuation in inlet level. The screw pumps are ideally suitable to handle this fluctuation in inlet level because the pump efficiency (hence energy consumption) is almost uneffected by changing levels. Also the screw pump will automatically pump less when the level in front of the pump decreases.
In the industry you can find several varied applications for Screw Pumps:
- Cooling Water Outfall Pumps
- Refineries: for oily sludge and waste water
- Potato processing industry
- Sugar industry
- many more …
Why do engineers select Archimedean Screw Pumps instead of centrifugal pumps?
+ Slow Speed, Simple and Rugged design
Probably the main and overall advantage of a screw pump is its superb reliability. The simple design, open structure and slow rotation speed makes it a heavy duty pump with minimal wear that operates for years without trouble.
Because of the open structure and large passage between the flights a screw pump can pump raw sewage without the need for a coarse screen before the pump. Both floating debris and heavy solids are simply lifted up. This saves considerably on equipment costs for a coarse screen or maintenance!
+ Can run without water
A screw pump can operate even when there is no water in the inlet. Therefore it is not necessary to install expensive measures (level control etc) to prevent ‘dry-running’’. The lower bearing does not need cooling.
A screw pump ‘scoops’ the water directly from the surface and does not need a collection sump. This keeps the pump head to a minimum.
The efficiency-curve of a screw pump is flat on the top. Due to that efficiency characteristic, the screw pump offers even high efficiency when it works at 50% of its capacity.
When incoming water-level goes down, at dry weather flow, the screw pump ‘automatically’ pumps less water. Ergo: no control system required to adapt pump performance.
The activated return sludge on STP’s is a delicate biological substance. Because of the low rotational speed and large opening between the flights, screw pumps do not damage this biological flock (whereas the high speed rotating centrifugal pumps will completely shred the biological flock).
+ Easy maintenance (no 'high skilled' staff required)
A screw pump requires very little maintenance. Compared to (submersed) centrifugal pumps it is next to nothing. Besides that no ‘highly skilled’ maintenance staff are required which makes this type of pump very suitable for remote locations.
+Long lifetime ( > 20-40 years)
Screw pumps with typical lifetimes of between 20-40 years are not unusual.