The Quick And Dirty Guide To Rotary Lobe Pumps

So, you've decided you need a positive displacement pump for your application (if you aren't sure yet, be sure to read our post on making the decision between centrifugal and PD pumps). But which do you choose? Not all positive displacement pumps are made equal. Each type, internal gear, external gear, rotary lobe, and others, have different purposes and intentions.

In this post, we'll discuss the rotary lobe pump, how it functions, and whether or not it fits your application.

ROTARY LOBE PUMP OVERVIEW

Rotary lobe pumps can be found in a wide variety of industries, from sanitary markets like food and beverage, to less than sanitary markets like wastewater treatment. Their popularity stems from a number of attractive properties like high efficiency, reliability, solids handling ability, and CIP and sanitary qualities.

Rotary lobe pumps are similar to the external gear pump. They operate in the same fashion, except that the rotary lobe uses "lobes" instead of gears to move fluid through the pump. Different types of lobes are offered depending upon the application. These types are: single, bi-wing, tri-lobe, and multi-lobe.

HOW IT WORKS

Two "lobes", driven by external timing gears, rotate independently to generate flow. Similarly to the external gear pump, the lobes rotate against each other to generate flow. Fluid flows into the pump, and the lobes hold the liquid in as they rotate against the casing before the fluid is forced out the discharge port.

WHAT THEY’RE GREAT FOR

Rotary lobe pumps are very popular in food applications because of their ability to carefully handle low shear fluids and solids, without damaging the product. Because the lobes do not touch, large particles are handled more easily than with other types of positive displacement pumps. It is also good for abrasive applications for the same reason.

WHAT THEY’RE NOT SO GREAT FOR

Low viscosity fluids are difficult for rotary lobe pumps. Clearances are not tight enough to efficiently handle these types of fluids.

THEIR BEST APPLICATIONS

This is a short list of some of the best applications for this pump:

Soaps
Paints and dyes
Wide variety of food applications (see a sample list)
Polymers
Paper coating

The rotary lobe pump is ideal for many applications across a wide spectrum of industries. Think it might be right for yours? Make sure you get the right pump for the job by talking to an experienced engineer. If you need help selecting the right pump for your application, ask us about it! We gladly provide technical assistance to businesses in Wisconsin and Upper Michigan.