What is a Screw Pump?
A screw pump is basically a screw-like pump based on Archimedes’ principle. Because of its simple mechanism, it has been used for water transfer since ancient times. The lower part of the pump is submerged in the fluid, and as the pump rotates, the fluid is gently lifted upward and discharged at the top. Archimedean pumps are commonly used at the beginning of wastewater treatment plants to provide the required elevation difference. These pumps are employed to transfer large volumes of fluid.
How Does a Screw Pump Work?
The lower part of the screw pump is submerged in the fluid. As the pump rotates, the fluid is slowly lifted upward and discharged at the top. Archimedean pumps are also used for transporting powders and grains.
What Factors affect the Capacity of a Screw Pump?
Screw installation angle
Distance between the threads
Screw rotation speed
Number of blade rows
Submersion depth
Screw diameter and other parameters
Applications of Screw Pumps
Water and wastewater treatment plants
Flood control
Management of the rainwater
Use in water complexes
Advantages of Screw Pumps
Long lifespan (between 20 to 40 years)
Very low maintenance costs
Does not require a highly skilled operator
Constant performance with variable capacity
The pump automatically adjusts its capacity according to the input level.
It can operate even without water at the inlet, as it does not require a level controller.
Capable of transferring materials containing solids without the risk of blockage
Product Overview
Screw pumps are a vital and highly sensitive device for transferring municipal sewage at the entry points of wastewater treatment plants. In view of the volume of urban wastewater, a reliable device with high transfer capacity, resistant to wear, corrosion, temperature, and with a long lifespan and ease of maintenance is crucial. The lack of such a device can result in sewage backing up into people’s homes. Screw pumps are based on the principle of Archimedes, and they are widely used throughout the water and waste water industry for the transfer of large volumes of fluids.
Due to its design, this device functions both as a screw pump, providing the necessary elevation difference at the start of wastewater treatment plants, and as a screw turbine for generating electricity in fluid transfer systems such as rivers with varying elevations.
In spite of its straightforward appearance, transferring wastewater with variable volumes, ranging from 50 to 3000 liters per second per screw pump, needs accurate calculations. The length of the pump is often over ten meters, depending on the elevation, and usually, 3 to 4 units are installed at each pumping station.
Given the fluctuations in wastewater flow rates due to city population and weather conditions, as well as the requirement to mount the device on two supports at varying lengths, accurate calculations are essential for each pumping station’s screw pumps, customized to the specific flow rate and elevation.
For fabricating each screw pump, elements such as pipe and screw diameters, the length of the bladed section, total length, axial and radial forces, torsional and tensile stresses, forces on supports and bearings, upper and lower shafts, bearing type and size, rotation speed, gearbox torque, electric motor power, and pulleys and couplings should be calculated.
Normandi Machinery is the first and only manufacturer of this device in the Middle East, having managed to complete all stages of design, construction, and operation since 2018.
Given that this device is one of the most crucial pieces of equipment in the country’s treatment plants, and considering that prior to this company’s entry into the screw pump manufacturing market, water and wastewater company managers were worried about sourcing, transporting (with sizes exceeding 12 meters and transport times sometimes extending up to two years), training personnel, and maintaining equipment and repairs under sanctions, these concerns have now been resolved.
An additional advantage of localizing this device is that all its components including sheets, pipes, bearings, shafts, electric motors, couplings, gearboxes, fan belts, and control panels are manufactured domestically.
Another advantage of localizing this device is the instant service provided for the duration of critical situations to water and wastewater treatment plants, such as in Qom, where two screw pumps went offline owing to bearing failures, and both were repaired and brought back online in a short time. Likewise, in Yazd, three screw pumps were damaged as a result of severe flooding, and a company expert arrived on-site within 24 hours to repair them.
Screw Pump Applications
No other device in the wastewater sector has as many advantages as screw pumps. They are highly sturdy, have low maintenance costs, and offer incomparable efficiency without a loss of suction power. Since water is transferred gently, it does not negatively affect sedimentation properties or floc structure, making it perfect for biological cultivation. This device meaningfully simplifies wastewater treatment and transfers raw sewage with the coarsest impurities, eradicating the need for supplementary screening at the pumping station. Though this device can handle many errors and faults, its optimum performance profoundly relies on the manufacturer’s experience.
A screw pump can be up to 25 meters long, lift water to a height of 12 meters, and transfer a maximum flow rate of 12,000 liters per second. Each unit needs separate design and calculations, and the most durable and efficient pump is designed using finite element analysis software.
Screw pumps can function reliably even in conditions with high sand content or acidic fluids.
Extensive Applications of Screw Pumps
Use in entry pumping stations of wastewater treatment plants
Irrigation projects
Drainage
Wetland restoration
Water parks
Use as turbines for electricity generation
One of the most imperative features of this device is its fish-friendly design. During the design, a thicker, rounded edge is formed at the beginning of the blades, producing pressure waves noticeable by fish, which keeps them away from the blades, allowing fish migration in previously impossible areas. Based on this unique feature, three screw pumps were ordered by the Gorgan Environmental Organization to restore the Gomishan Wetland, letting water and fish to be transferred from the sea to the wetland without any problems.
Market Demand Studies
The screw pump is a strategic device in the water and wastewater industry, produced by major companies such as Spaans Babcock in Spain, Ritz in Germany, and Landustrie in the Netherlands. Due to the country’s sanctions and:
The noteworthy alteration between foreign currency and the Rial
The challenges in importing the device due to its size (often over 12 meters long)
The lack of technical support from Western countries
The absence of in-person staff training
There are 194 wastewater treatment plants in Iran, and only 21 of them have screw pumps. The total number of screw pumps in the country is about 133, and the population served by the treatment plants with screw pumps is roughly 25 million people. This shortage of screw pumps is specific to the water and wastewater sector, while screw pumps are also used in aquatic systems and in controlling rainwater and floods. For years, the production and sale of these devices have been monopolized by a few European countries, with Iran being one of the importers. At Normandi Machinery, by manufacturing these devices and successfully passing tests, we have been able to break the production monopoly, allowing Iran to become a producer of screw pumps in the world.
