A screw pump, also called a water screw pump, is a positive displacement (PD) pump that uses one or more screws to move solid or liquid liquids along the axis of the screw. In its simplest form (Archimedean screw pump), a single screw rotates in a cylindrical cavity, thus moving the material along the main axis of the screw. This old construction is still used in low-tech applications such as irrigation systems and agricultural machinery transporting grain and other solids.
The development of these types of pumps has led to various multi-shaft technologies, in which carefully crafted screws can rotate in the opposite direction or remain stationary in the cavity. Cavities can be created to create cavities in which the pumped material is “trapped.”
Parts of the Screw Pump
A screw pump has the following parts:
Timing gears driver screws (male rotor) and driven screws (female rotor) work minimally. They always tend to interact; one of these contacts covers the edges of the screw, which dramatically reduces the outlet pressure. Without control, he will not only be able to evacuate and become more inefficient. Instead, in some cases, it also activates the screws to lock them together. Therefore, a timer is mounted on the screw to acknowledge such events.
Usually, the timing gear rotates the gear in this way. It is not caused by metallic contact between the male and female rotor components. It also ensures no such contact, even if the screw pump is running for a short time. The three-screw pump design was useless at the time.
The two external screws remain free, while the central drive screw creates the movement of the acid liquid.
1. Suction port and Discharge port
The screw pump has different suction and discharge ports because the fluid flows along the axis of the screw in the discharge port. The intake and exhaust ports are designed this way. When the pump stops completely, it contains enough fluid. This helps provide initial fluid flow to the pump. Avoid drying for a short time, even if the suction tube is empty or dry. The suction port is in a small vacuum. This is due to the pressure variation between the suction port and the pump inlet.
This provides a necessary movement for the liquid environment, trapped in small spaces between the screws in different enclosed areas. On the other hand, the output is under much pressure. In all cases, the pump pumps more fluid. For this reason, the pump delivery vortex is always more significant than the suction vortex.
2. Relief valve/recirculation line
As a subset of positive displacement pumps, the screw pump creates pressure even if the outlet is closed. This can have serious consequences: the pump and connected machinery are destroyed, and the operator is injured. All positive displacement pumps, including this one, are equipped with safety valves to create a sense of protection for the pump, connected machines, and operators. Another standard method of neutralizing excess pressure is recirculation through the outgoing fluid.
3. Driving shaft
It is part of the pump and connects the screw pump assembly to its drive motor. This is done using the appropriate set of flexible couplings. In many pump models, the motor shaft is an integral part of the pump. Turn the bolts and reverse and tighten. In this design, these drives are supported by a series of axle mounting bearings. To ensure the pump’s longevity and its bearings, the pump shaft must be properly aligned when installing the pump.
Advantages of the Screw Pump
The screw pump has several screws that, when turned, snap together to form a sealed hole in the pump casing. When the screw is turned, the liquid moves continuously through the pump. This creates a constant flow, independent of pump pressure or viscosity, which can reduce the speed of the centrifugal pump.
Some of the advantages of screw pumps are:
- Sequences of different flow rates, pressures, fluid types, and viscosities
- Continuous stream
- High volumetric efficiency
- Controlled exit
- Low internal speed
- High resistance to air or stretched gas
- Soft and silent performance
- Very low heart rate
- Automatic properties
- Reduce device vibrations
Difference between a centrifugal pump and a screw pump
The centrifugal pump uses a propeller, which is ideal for high-transfer applications and water-like liquids that need to be pumped at a variable rate through a network of pipes. Based on its engineering principles, it’s easy to see why many operators rely on centrifugal pumps for many typical liquid conveying applications. However, we all know that different pumps are often better suited for different jobs.
Screw pumps have become more prevalent in some industries, where standard centrifugal pumps cannot provide the required flow and energy efficiency or have difficulty transporting high-pressure fluids and other materials. It often affects performance.
Double screw pumps and triple screw pumps are designed with positive displacement. They are more versatile and reliable in various applications, especially in oil and gas, petrochemical, and chemical industries, where centrifugal pumps often consider viscosity.
Check out: What is a Hand Pump? Types and Working