PUMPS DON'T SUCK! And Other Centrifugal Pump Basics

Centrifugal pumps cover a broad category of pumps because they vary so much in size, capacity, and ability. You'll find centrifugal pumps in several forms, like standard end-suction, submersible, and self-priming (pictured to the right), and in a variety of applications. 

Let’s get back to basics and understand how centrifugal pumps work, what they're good for, and why "pumps don't suck" (except when they don't work).

HOW A CENTRIFUGAL PUMP WORKS

Centrifugal pumps move fluid by using centrifugal force to generate velocity of the liquid. Fluid enters the pump through the suction nozzle, into the eye of the impeller. The impeller vanes catch the fluid and rotate it, both tangentially and radially until it exits the pump on the discharge side. As the fluid leaves the pump it's under greater pressure than when it entered. Now, does the impeller do ALL of the work? No, it's only a part of the hydraulic design of the centrifugal pump. The impeller is only useful if the liquid being pumped is controlled by the volute. The volute is another part of the hydraulic design that transforms the velocity of the liquid into pressure and controls the pumped liquid as it's discharged from the pump.  

Remember: Pumps DO NOT SUCK liquid into the pump. Rather, atmospheric pressure pushes water into the pump keeping the liquid in its natural state (picture below courtesy of Gorman-Rupp). Even self-priming pumps don't suck liquid into the pump. Because of their design and ability to handle air, atmospheric pressure pushes liquid into the pump by lowering the pressure on the suction side of the pump.

BEST APPLICATIONS

Centrifugal pumps work best for water and other low viscosity fluids. When pumping viscous fluids, pump efficiency is significantly reduced. On the other hand, they have a greater tolerance for solids than positive displacement pumps; some are even built to pass solids greater than 10” in diameter!

ADVANTAGES

Centrifugal pumps are great for moving a high volume of low viscosity fluids at fast speeds. With such a wide variety of options, it isn’t hard to find a centrifugal pump that's right for just about any application.

DISADVANTAGES

Centrifugal pumps are very sensitive to operating conditions. Equipment vibration, unbalance, and cavitation are just some of the factors that can cause a centrifugal pump to literally self-destruct, as we cover in our most downloaded eBook, 36 Ways to Kill Your Pump. 

It's a known fact that centrifugal pumps aren't ideal for EVERY application out there, so be sure to speak with a qualified engineer when selecting a pump.

You can read more about centrifugal pumps by downloading our eBook, the Must-Have Handbook for Centrifugal Pumps below. Check it out today!