When pumps are on large systems involving many components, initial start up is a time of both excitement and anxiety. Whe mishaps occur, resolution can't come fast enough especially when on a brand new $100 million paint operation.
We were starting up a new system in an automotive paint shop, spray stage. The pump was sized for 1400 GPM @ 80’ or 35 PSI, we were immediately getting 20 PSI at the discharge. Holding constant. Now, pumps are dumb as we like to say. They will run on the curve. It just depends on back pressure..what you’ve done with piping and nozzles and filters after the discharge. If you deadhead a pump by closing the discharge you will get maximum pressure and no flow obviously. At the other extreme, if you connect nothing to the discharge you will see maximum flow at low pressure.
So on this day we had a hunch that something was allowing more flow than expected. We followed the discharge and counted the headers in the tank and the eductors and realized the contractor installed two extra headers with 15 extra eductors on each header, causing way more flow than design and which allowed the pump to “run off its curve.” We removed the extra headers and the pump ran smoothly at correct 35 PSI.