Pump selection: Choosing the right pump for viscous fluids

Just because the pump works doesn't mean it is right.

By Dirk Willard

Let’s look at pumping of viscous liquids — and limit our discussion to pumps for regular processing, not metering or sampling.

Viscosity in pumping is a great bugaboo of our business. Most pump manufacturers will tell you not to use a centrifugal pump for liquids with viscosities beyond 100 cP. And, despite what I witnessed, let’s agree that a centrifugal pump usually isn’t a good choice for viscosities above 100 cP, let alone 300 cP. Such services generally call for some type of positive displacement pump. These pumps are self-priming.

A good choice often is the lobe pump. It’s a rotary pump good up to its maximum case pressure; it can handle a maximum of perhaps 2,000 cP (which is about the viscosity of honey at 25°C).

To learn more, read "Pumps: Get Into the Thick of Things" from Chemical Processing.

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