You’ve heard the term, but what is an Archimedes screw pump? How is it used in hydropower or waste treatment? Why is it called an Archimedes screw pump? Did he invent it? We have answers to all of your questions.
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. They move more than water, though that was the original purpose.
Why is it called an Archimedes screw? Historians believe it’s because Archimedes, an Ancient Greek engineer, inventor, and physicist, invented the system. Not only did he develop the technology behind a screw pump, but he also created compound pulleys. How were people in those times using his screw pump?
- It was used to continually drain water from a bilge on the Great Ship of Hieron, the King of Syracuse. Syracuse was the city in Sicily where Archimedes was born. Onboard, one man was assigned the task of turning that screw pump to keep draining water from the ship. This screw moved water from a lower point to a higher one.
- It became the ideal way to move water in the Nile Delta for irrigation. While crops were grown on banks high above waterways, screw pumps would draw water from the rivers to make sure crops didn’t dry up in the arid region.
- Another early use of the Archimedes screw pump was to remove water from deep within Egyptian mines to protect the miners. With water pumped away from them, the risk of drowning reduced as workers went underground to mine everything from copper to gold.
How Do They Work?
How does it work? Wouldn’t gravity pull the water right back to the water source? An Archimedes screw system has a large screw that sits within a cylindrical shaft or sits in an open chute. The bottom thread of the screw sits in the lower water source and scoops some water. As the crank turns the screw, the motion forces the water to propel to the next thread.
Each turn continues propelling the water further up the screw conveyor until it reaches the place where it is deposited. As long as the motion continues, the water will keep propelling to the top and get deposited to the higher area. The speed of the pump and the width of the threads help determine how much water can be moved.
Archimedes screw pumps move more than water. They can move plastic pellets, grains, sludge, and other fluid items. If an item is fluid enough to move, a screw pump with the right dimensions and pump speeds will move them from one level to the next.
Examples of Places Using Archimedes Screw Pumps
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.
You’ve likely seen farm equipment that shoots ground up corn into a farm truck where it’s transported to silos. The corn that shoots out of the raised tube reaches the top of the chute thanks to an Archimedes screw pump aka screw conveyor.
In England, there is a man-made white water rafting center called Tees Barrage. Visitors learn about white water rafting in two long courses. Four Archimedes screw pumps move close to 3,700 gallons of water each second to create the river. The pumps move the water from the lower pools to the top of the course creating close to 1,000 feet of white water before a tremendous drop. When you’re done, you can use a conveyor to follow the water back up to the top while in your raft and tackle the course all over again. As long as the pumps are doing their job, the water will keep flowing in an endless loop.
Windsor Castle’s power is supplied through Archimedes screw pumps. A 40-ton screw pump brings water from the Thames to two turbines that have gearboxes and generators to convert the energy of the water to electricity used within the Queen’s castle.
The screw pumps at Windsor Castle generate around 1.7 million kWh each year and are estimated to help reduce carbon dioxide emissions by more than 1.74 million pounds. It’s a green way to bring power to a huge castle and could easily do the same for hundreds of homes. If your town or city is looking into energy-efficient hydroelectric systems to provide power to homes and businesses, screw pump turbines are a must-have.
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. The process for cleaning sewer and septic liquids involves several steps.
Wastewater enters the plant from trucks that pump it out at homes with septic systems or through the sewer where it’s pumped into the primary settling equipment. Screens remove some of the material, such as grease chunks, where they travel by truck to landfills. Grit is removed and also taken to the landfill. The remaining sludge is pumped into aeration tanks. Additional solids are also removed by truck. The liquid goes to another settling tank before it’s disinfected and pumped out to waterways.
What about the sludge? Archimedes screw pumps help there too. The sludge is pumped into digestion tanks where resulting methane gas can be used to provide power. Water separated from the sludge continues to aeration and disinfection. The design of a water treatment plant may vary depending on a town or city’s population and the acreage your plant has available.
They can pump stormwater, drain waterlogged land, and are useful in industrial settings where water needs to move from a low area to a higher one. A screw pump can also be a big help at separating the water from the sludge.
Open vs. Enclosed Screw Pumps
What about the screw pumps themselves? What are your options? 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.
Why would you want one over the other? Enclosed screw pumps are quicker to install. You don’t have to build the trough from concrete and wait for it to cure. You could use a steel trough instead, but there is still going to be the installation time to consider. With an enclosed screw pump, the screw is already situated in a tube. It’s a quick and easy drop-in placement, which also makes for fast replacements.
An open screw pump needs space. If your water treatment plant, hydropower plant, or other business doesn’t have a lot of acreages to work with, you’ll need equipment that takes up less space.
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 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. Working with an expert in screw pumps ensures you get a cost-effective design with maximum efficiency and output.
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 affected 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, but Lakeside Equipment can get you to an inclination of 22 to 40 degrees if needed. 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. Screw speed is the number of revolutions that screw makes each minute. Finding the right screw speed 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 believes you should never choose a pump with requirements that exceed 90% of the recommended HP listed on the motor.
How deep is the level of water or liquid you’re pumping? An open screw pump will work whether or not the bottom of the screw is submerged in water.
The screw itself is something to consider. You can get screw pumps in single, double, or triple helix designs. The tighter the threads on the screw, the more fluids the screw will grab and propel upwards. A single helix has the threads farther apart so the output is lower. A good rule of thumb is to expect output to increase by 25% for each helix you add. Triple helix designs are best when you have multiple flights, and a single is best when you only have one flight.
Screw speed impacts efficiency. You don’t want to exceed the maximum screw speed or you risk cutting efficiency by increasing your plant’s electricity usage. If this happens, it’s best to install multiple screw pumps to handle the extra load.
The final factor to consider is safety. You don’t want a worker getting injured falling into equipment. Safety measures must be part of your plans. Handrails, stairs, and barriers are all important. The power controls also need to be placed so that the screw pump doesn’t turn out at the wrong time. You want qualified engineers working with you to make sure safety is a key component in your design.
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.
