The Archimedes screw has been used for ages to move water from a place of lower elevation to another at a higher elevation. Originally, it was operated by hand. Today, the pumps can be powered by wind energy, solar power, or an electrical motor.
This system has a large screw that sits within a cylindrical shaft or sits in an open chute. The bottom of that screw sits in the lower water source. Turning the crank puts the screw in motion. Water collects on the lower thread and is propelled upwards to the top of the cylindrical tube or trough through the continuous motion.
You’ve probably seen Archimedes screws at work. They’re used in snow blowers to propel the snow through the chute where it can be directed to a bank or roadside. They’re used in chocolate fountains to push the melted chocolate to the top of the fountain where it flows down the tiers and back to the heated collection pool where it travels back up and repeats the process.
Archimedean screw pumps are used in waste treatment plants. As the gap between the screw blades is wide, they can cut through solids without clogging. They can pump storm water, drain waterlogged land, and are useful in industrial settings where water needs to move from a low area to a higher one.
Open vs. Enclosed Screw Pumps
There are two types of Archimedes screw pumps. If the screw is enclosed in a pipe, it’s an enclosed screw pump. With an open screw pump, the screw sits in a concrete trough and is open to the environment.
Enclosed screw pumps come in a choice of Type C or Type S. Type C has the screw sitting within a tube that rotates. As a result, the Type C pump can sit at an angle of up to 45 degrees, which takes up less space. Type S must be at a 22 to 40 degree incline as the tube is stationary. You can opt to mount the tube on a pivot to allow it to be raised or lowered in order to change the pumping rate. Other advantages are:
- Higher efficiency
- Option for drop-in replacements of older equipment
- Lower installation costs
With an open screw pump, the trough needs to be at an incline of 22 to 40 degrees. The screw has upper and lower bearings that help it rotate. There’s also the drive assembly. Self-aligning bearings can be submerged or not and keep maintenance to a minimum by having permanent lubrication to prevent wear and tear. You also gain these benefits when choosing an open screw pump:
- Up to 75% efficiency for most of the operating capacity
- Do not close or need pre-screening
- Minimal maintenance
Factors to Consider When Choosing an Archimedes Screw Pump
An Archimedean or Archimedes screw pump is designed to meet your needs, but you need to consider a few factors when making your final choice.
Start with the capacity you’re aiming to meet. How much liquid are you moving from one flight (level) to the next? This needs to be clear several other factors are considered in order to ensure the screw pump design matches your goals. If you pick a screw pump with too small of a screw, the capacity will be effected by the smaller diameter.
As the screw pushes the liquid up the trough or tube, the angle cannot be too steep. If you have too steep a slope, the liquid will continue to leak back to the lowest pool. Most screw tubes are set at an angle of 30 to 38 degrees. To keep the incline at the right angle, you’ll need to have enough flights to maintain that level of incline. Your capacity increases by around 25% for each flight you add to your design.
How fast do you need the screw pump to work? If the screw isn’t rotating fast enough, the liquid will overflow and return to the bottom chamber. If it’s too fast, it can be just as wasteful. Finding the right balance helps the system remain efficient and lowers energy use. The correct horsepower helps here. You need a pump motor that lifts the liquid at the right rate and handles your desired capacity.
Lakeside Equipment sells both open and enclosed screw pumps. Lakeside Screw Pumps are made in the U.S. and designed to be around 70% efficient, which reduces your energy use. We pride ourselves in supplying affordable screw heads that remain easy to use and maintain. Give us a call. We can help you find the right Archimedes screw pump for your needs. Reach us at (630) 837-5640.