Cavitation & Aeration


In this lesson we will discuss the terms starved pump and flooded pump, describe the process of cavitation and how it causes mechanical erosion, and explain areation and its impact on a hydraulic system.

Starved or Flooded?

Whether your pump is positive or non-positive displacement, providing the best possible conditions at the inlet is vital to reaching maximum pumping efficiency, as well as prolonging the life of your pump.

The Reservoir

Let's start with the reservoir itself. Take a good look at the breather cap on top of it; that cap is very important! In good condition, it allows air to flow into the reservoir to make up the pump draw. Without it, the pump would create a vacuum condition along the inlet line and reservoir.

Breather/Filler Cap
No Output
-1.2 psi Vacuum
Hydraulic Pump
3 Feet

This pump has a starved inlet. It is not able to put out flow, and it is in danger of cavitation.

Starved Inlet

There are a few ways to cause a starved inlet (plugged breather, too long of an inlet hose, poor placement of the reservoir), but they all result in the same problem. The pump is drawing in less fluid than it is trying to displace. Not only will a pump with a starved inlet not be able to put out much flow; it is in serious danger of cavitation.

A starved inlet is very, very bad for a pump.

Flooded Inlet

The opposite of a starved inlet is a flooded inlet. A flooded inlet occurs when there is more than enough liquid at the pump's inlet, to the point where it's even holding a positive pressure against the inlet (1.2 psi is about ideal). As the pump turns, fluid rushes into the pumping chamber, keeping it fully charged.

Good system design will create a flooded inlet. Keep it in good shape by mainting a clean breather!
Steady Output
Hydraulic Pump
1.2 psi
3 Feet

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Vacuum Pressure
Drain Pressure
Low Pressure
Medium Pressure
High Pressure
Lowest Voltage
Medium Voltage
Highest Voltage
Magnetic Field
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