Hi. I'm Mike Austin, Service Manager with the Gorman-Rupp Company. This video, and
future videos, will inform and instruct into the operation and troubleshooting
of self-priming centrifugal pumps.
Before we get started, let's review the piece of
equipment we'll use for our priming demo; it is the glass-faced pump. The-glass faced
pump consists of our very own 11 1/2A3E 1.5 single-phase unit
driven by a variable frequency drive. It is the exact same 11 1/2A3
that we build on a regular basis here at Gorman-Rupp, with one small
exception; we have taken this particular pump, the 11 1/2A3, and we have
sectioned the volute casing at the same location where the wear plate is
installed. We have mounted a bulletproof lexan face and maintain the same
clearance between the impeller and the lexan face. With this glass face, we can
now see what occurs inside during operation of the glass-faced pump.
Included outside of the pump itself is glass piping. Mounted to the suction line
of the glass-faced pump is a vacuum gauge. Mounted to the discharge side is a
pressure gauge. Also included in the glass-faced pump is a stroboscope to measure speed.
With the speed of the pump, and with gauge readings, we can then plot
condition points on a curve and troubleshoot accordingly.
Let's go ahead and get started with the subject of our video in priming.
We'll open both air vales,
inducing air back into the system, allowing the liquid to fall back to the
amount of water that we normally place inside the pump for priming.
For those of us that are familiar with self-priming centrifugal pumps, we know that we must
first fill the volute with water. We can now start the pump
and watch what actually occurs inside of the pump during priming.
After we fill the volute casing with water and we energize the pump, the impeller turns in
a counterclockwise rotation. The initial prime of the pump is slung through the
volute scroll, or the ever-increasing water channel, into a pressure cavity or
a discharge chamber inside the volute. Inside this discharge chamber, the air
and water separate. The heavy water falls back down through a recirculation port
and the air then is evacuated through an open-ended line or through an air release device.
All the while that we recirculate the water inside the casing
and remove the air from the top, we create a low pressure at the eye this impeller.
Due to differential in pressure, atmospheric pressure that we
live around every day is higher than the lower pressure created at the eye of this
impeller. Due to that differential in pressure, atmospheric pressure outside
begins to force liquid up the suction pipe. As liquid moves up the suction pipe,
it pushes all the air ahead of it into the volute casing, where it is handled
through the recirculation process. Again, the air is handled off the top and the
heavy water recirculates back down into the volute scroll area. I'll close this
valve right now and create a suction line capable of pulling a vacuum.
Ahead of it moves the air, pushes it into, handles it through the recirculation
process, and once the water arrives, the pump then goes to complete operation.
For more information on pump hydraulics, equipment or application
engineering, watch Gorman-Rupp's YouTube Channel, and visit us at GRpumps.com.