If you’ve ever fallen asleep reading pump texts about NPSH, you’re not alone. But here’s an easy-to-understand, graphical approach to ensuring your calculations.

A key advantage of rotary positive displacement pumps is providing consistent flow regardless of changes in liquid viscosity or differential pressure. But should a downstream blockage occur, pressure will rapidly build and may exceed the rating of the pump, drive equipment, system, or any combination thereof, with the potential for damage and unplanned downtime. For this reason, overpressure protection must be used, and pressure relief valves are the most commonly used form of overpressure protection for rotary positive displacement pumps.

With Viking pumps the answer is usually “yes,” but before you turn that “reverse” switch on your pump’s motor starter or variable frequency drive, there are a number of things to consider, which are discussed here

All positive displacement pumps work by first expanding a cavity between the casing and one or more moving parts to create a partial vacuum, so atmospheric pressure can force liquid into the pumping chamber through the inlet port

Customers don’t ask me to listen to quiet pumps. This is symptom #1 of a cavitating pump. The pump is loud. Descriptors like “growly”, “rumbling”, or “gravelly” are used to describe the atypically loud sound coming from the pump.

“Does it always sound like this?” I ask.

“No, it was fine in the fall, but it’s been loud all winter.”