Chicago Fire Department

[GA_Dave]

After comparing the high pressure pump panel to a standard CFD pump panel, I conclude the following:



The chrome handwheel above the main intake is the changeover valve, from pressure to volume. As already stated, the three gauges to the far left, rated for 1000 PSI, are for the third stage. The top one is overall 3rd stage pressure, like a master gauge. The other two 1000 PSI gauges and the two chrome handwheels on the left are for each of the two high pressure discharges, likely located on the curb side pump panel. High pressure is only available from these two discharges, answering the question in Post #1631. Total rated pump capacity is 1500 GPM, with 450 GPM available @ 600 PSI. I haven't been able to locate the switch to engage the third stage, but I would guess that it is electrical, not manual. A typical 3-stage pump is not simply a pump with three impellers, it's more of a two stage pump with a single stage pump attached to it.



BTW, impellers always move water the same way. The changeover valve opens and closes valves that route the water differently. In Volume (Parrallel), water is directed to both impellers simultaneously, the impellers speed it up and send it to the discharges. In this case, it would be 1500 GPM at 150 PSI. In Pressure (Series), the water is routed to one impeller, it is sped up, then routed to the other impeller, where the speed is doubled, and then discharged. In this case, 750 GPM at 250 PSI. When the third stage is used, the water is routed from the second impeller to the third, where it is sped up once more. Due to the plumbing and size of the third stage impeller, the flow is reduced but the pressure is increased, in this case to 450 GPM at 600 PSI.