This is a gear pump, a type of rotary positive displacement pump. Its tight-fitting clearances allow it to evacuate air in the suction line to prime the pump. And once primed, it's capable of pulling even higher vacuums. This ability to self-prime is key in applications like unloading drums, totes, rail cars, and barges. But as good as this pump is at pulling the liquid in, it's always going to be limited and not based on the pump. It's based on an invisible force pushing the liquid in from the outside, and that's atmospheric pressure.

Hi! I’m Chad Wunderlich with Viking Pump and this is an internal gear pump. With each rotation of the gears, a set volume of liquid is moved from the inlet to the outlet. And if I were to reverse the direction of rotation, I reverse the direction of flow. Now this isn’t unique to internal gear pumps, other rotary pumps like external gear, lobe, and hose pumps exhibit this same behavior. But did you know it’s possible to make this internal gear pump deliver flow in just one direction, independent of the direction of rotation?

Join Viking Pump's Chad Wunderlich as he describes the multiple ways to address and solve for a cavitating pump. 

So just to recap: a cavitating pump is one that is exhibiting noise, loss of capacity, and if left unchecked can lead to localized pitting of the pump internals. The cause is excessive vacuum at the pump inlet. So what's the fix? 

For most systems, it starts with atmospheric pressure - but you can't move your entire facility to sea level. So what CAN you fix?

In this Pump Report, Chad covers the causes and symptoms of positive displacement pump cavitation.

Hi, I'm Chad Wunderlich with Viking Pump. In a previous video we discussed the priming capability of positive displacement pumps, like this gear pump. This is due, in part, to the pump's ability to develop vacuum...but what happens if that vacuum gets too high? 

Today we're going to talk about cavitation. You're watching the Pump Report. 

In a positive displacement pump, each rotation of the shaft and gears carries a fixed volume of liquid from the supply tank to the downstream piping. When paired with an AC induction motor, speed and flow are very consistent. But what if you want to CHANGE the flow? In this episode of the Pump Report, Chad discusses controlling your positive displacement pump's motor with a variable frequency drive - or VFD.