Generally characterized by noisy operation, and excessive vibration, air inside a pump can have some seriously undesired results.
As the percentage of gas by volume increases, the performance of the pump decreases. According to the Goulds Pump Care Manual, a mixture of only 2% gas by volume will cause a 10% drop in capacity. If you've noticed a drop in performance, or "gravel" type noise when the pump is in operation, you may have air inside.
Not only will pumps with entrained air experience a drop in performance, serious cases will cause shaft breakage, seal failure, or accelerated corrosion.
So how did air get inside of the system? Below is a list of just some of the ways air could be creeping inside.
Air can easily enter pumps through leaks in the suction line at elbows, joints, etc. It's safe to say, if fluid is coming out, air is definitely getting in.
NOT MEETING MINIMUM SUBMERGENCE
Submersible, immersible, or pumps in suction lift applications can be prone to air entrainment when the minimum submergence level in the tank/pit are not met. When the fluid level in the tank or pit meets a certain level, a vortex can form.
This video from Gorman Rupp does a good job showing how a vortex can form on the surface of the water and make its way all the way up the suction line to the self-priming pump above.
The amount of air that can be handled by a pump varies from pump to pump. But one thing is certain, all fluid handling pumps operate better when no air is present.
If you're experiencing issues with a pump making too much noise, or vibrating excessively, ask us about it! We gladly provide technical assistance to businesses in Wisconsin and Upper Michigan.