Hello. I'm Jeff Hannan, Eastern District Manager for Engineered Systems.
Here we are back at the priming tower and what we want to show this time is what effect
entrained air can have on a pump suction line and the performance of a pump.
A lot of times in wet well design, you'll have an invert that's dropping water into a wet well,
maybe a couple hundred gallons a minute dropping from eight or ten feet
in the air down into the into the wet well. That water splashing into the wet
well creates a lot of turbulence, creates a lot of air that gets trapped in the
water and if that's occurring very close to the suction line or very close to a
submersible pump, that air can sometimes cause a submersible pump to become air
bound and lose its pumping capability. It can also introduce so much air on the
suction line of the pump, it causes the pump to be air bound and to demonstrate that,
we're going to go ahead and start this pump up and then I'm going to direct the
discharge line by opening a valve. I'm going to direct my discharge over near
the suction of the pump. By opening the valve,
we're going to direct some flow
and direct it directly at our suction line. You can see a lot of air in the water.
You can see a lot of turbulence there, and a lot of those air bubbles are
getting picked up and sucked up the suction line and going right into our
pump and you can hear the pump. There's a little bit of noise associated with the
pump now as the air is working its way through that pump. There's a hydraulic
imbalance inside of the pump now that overtime could cause some varying issues,
but more importantly, it could cause a pump to lose its prime.
Now this is a self-priming pump by Gorman-Rupp. It's designed to handle a certain amount of
air, so it can take care of a lot of air and keep itself pumping, but you can
occasionally hear it coming in and out of a partial prime situation.
If this were a submersible pump and when the air would get underneath the submersible, it
could cause that submersible pump to be air bound almost immediately and stop
the flow coming out of the pump station
and that pump would trip out on a high temperature,
but again in the smaller wet wells, especially where an invert is dropping
near a suction line, the splashing of the water
can cause you some problems in the pump station.
In conclusion, air entrainment is something to be mindful of in a wet
well, especially as smaller wet wells, so you're having the invert dropping in
there the two suction lines. Typically, a good way to determine if entrained air
is causing your pump to lose its prime if you're only experienced the problem
with one pump shutting down on high temp, the other pump whose suction line is
further away from the invert or where the splashing of the water and the wet
well is occurring, if that pump is working without any problems, then typically it's
a good indicator that you might want to put a redirect the flow of water into
the wet well away from that suction line and make sure that that pump is not
getting too much air around the suction line because of the splashing of the water.
Thank you.
For more information on pump hydraulics, equipment or application engineering,
watch Gorman-Rupp's YouTube Channel, and visit us at
GRPumps.com