PARALLEL / PUMPING IN VOLUME
The second mode we will look at is our pump running in parallel.
When our two-stage pump is running in parallel, the two impellers are now "running together," or "next to one another," or "side by side." In Pressure mode, our impellers were stacked... now, they are split. Now, the physical properties of our pump haven't changed in terms of "stacking" or "splitting" our impellers. Instead, we accomplish this in how we route water via a simple clapper valve).
As water enters the intake side of our pumps, it is split/routed into two pipes, feeding both impellers simultaneously. Both impellers rotate at the same RPM (because they are on the same drive shaft) and produce the same volume (GPM) at a given RPM which ultimately increases in volume since both impellers are discharging their capacity.
If this is confusing, let's go back to our simple scenario and see if this helps.
Back To Our Simple Scenario...
We have the same 50psi hydrant feeding our Engine via a 5" supply hose.
If impeller #1 produces 500 @ 100 psi...
Then impeller #2 produces 500 GPM @ 100 psi as well...
Combined they will produce 1,000 GPM @ 150 psi (50 + 100 = 150)
ADDITIONAL RESOURCE:
In the following Episode from The Urban Pump Series, we cover Dual Stage Pumps and in more depth this concept of pumping in Volume/Pressure:
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PUMP SCHOOL W/ RICK BREWER
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