Screw pumps are a common type of pump that is used for moving viscous fluids. Using two or more screws, they take in the fluids and then push them to the other side, whilst also pressurising. Screw pumps are generally available in two types: double screw pumps or triple screw pumps. Both work in slightly different ways and are better suited to various liquids. Whether you are using a double or triple screw pump, you will need to know if they require priming or not. The simple answer is that all types of screw pumps are self-priming, but it is crucial to understand why.
What Does Priming A Pump Mean?
Before we can consider why a screw pump is self-priming, and what this means for the pump’s performance, we need to be clear on what priming a pump means. Priming a pump is when the impeller of a centrifugal pump is completely submerged into liquid, and all air is removed. This process must take place before the pump is started again after being shut down. Failing to prime a pump can result in many issues with its performance and ultimately lead to failure.
A screw pump is self-priming, meaning this process doesn’t need to take place. This is because of the vacuum that is created within the pump. If a screw pump does become dry and continues to be used, it will cause damage. Eventually, dry running a screw pump will leave it irreparable.
How Does A Screw Pump Work?
These types of pumps use screws which intermesh and pressurise the fluid. Double screw pumps have two intermeshing screws that take in the liquid and push it to the other side. With these, the screws have no contact with each other, making them suitable for more types of liquid. Triple screw pumps have one driving screw which is intermeshed with two other screws. They work together to build pressure and move the liquid. With a triple screw pump, the screws do have contact, which means you can only use them to move clean liquids. Screw pumps are perfect for handling viscous fluids which a centrifugal pump wouldn’t be able to take. An industrial level screw pump will handle viscosities up to 10,000 cSt, compared with a centrifugal pump capable of up to 760 cSt.
As experts in all types of pumps, our team are on hand to help you find the most suitable screw pumps for your requirements and answer any questions you may have.