What is a screw pump?
A type of positive displacement pump that uses two or more intermeshing screws to pressurize fluids in order to move them in a system. The screws then push the liquid out the other side with increased pressure.
Screw pumps have their origins in the Archimedes screw, which was invented by the Greek scientist in the 3rd century BC. The Archimedes screw moved water for irrigation using a single screw that fit into a cylinder with minimal clearance. Today, few types still use this design - most use at least two screws.
How do they work?
There are two main types:
1. Double screw pumps involve two intermeshing screws. The pump is normally equipped with a set of timing gears, located outside the pumping chamber, and lubricated with clean oil, to ensure that the screws are rotating correctly relative to each other. With this arrangement, the screws are not required to be in direct contact with each other.
2. Triple screw pumps have one driving screw intermeshed with the other two screws to create pressure. The screws contact with each other, which limits the pump to handling only clean liquids.
Where are they used?
Screw pumps are the largest type of rotary positive displacement pump and they can deliver higher flow rates than other types. They also have a variety of uses.
For example, high-powered versions are used in oil production applications to transport crude oil from an oilfield to a processing plant. In this application, one of the features is the pumps ability to handle fluids mixed with gases. Produced oil often includes natural gas, so these pumps are used to ensure the gas doesn’t have to first be separated from the crude oil before the product is pumped to a processing plant.
They are often chosen to pump fuels and oils at high flow rates and are also commonly used as the hydraulic pump in elevators.
Here are a few screw pump manufacturers to consider.
RedScrew manufactures a variety of screw pump and related technology for the process, marine, energy, and transport industries. The company makes several models of twin screw pumps including its WTG Series for a wide range of fluid types used in the chemical, petroleum, and food & beverage markets. The pump has a max flow capacity to 10,000 gpm, a max differential pressure to 900 psi, and allows for max temperatures to 650 degrees F.
RedScrew also offers its NTG, Triple, Multiphase, and Specialty Series screw pumps. Each pump offers specific features and advantages for their specific target applications. The NTG Series is manufactured to pump lubricating fluids with high viscosity, making it ideal for use in oil terminals, petro-chem, chemical fiber, shipping, asphalt, and heavy fuel oil markets. The screw pump can handle up to 2,200 gpm flow and pressure up to 230 psi.
So now what do you do? As many of you know, this is a fairly common occurrence, particularly with pumps that have been around a long time. Here's some advice on what to do.
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