Gpm....psi....etc....a little help

N

NJWashingGuy

New member
I was reading that adjusting your unloader also cuts back your flow if you lower the pressure that the machine is capable of...... if that is true, how would one run 8gpm at 1300 psi on a machine capable of making 8gpm at 3000 psi??

Pumps are rated for gpm by rpm correct?? If so......

Horse power is the limiting factor in the PSI that can be made correct?? so....

Is it possible to get 8gpm out of a 25 hp Hydrotek skid at 1300 psi......?? If so how??

Thanks for any help and if what I was reading is wrong.....someone tell me please.

Thanks, Mike.
 
You need to learn how to read a nozzle chart. Don't feel bad. I have a local major supplier who's head salesman says a 8 gpm 3,500 PW can only change pressure by engine speed. How many PSI do you think a 8 gpm PW is putting out when you run it without any nozzle? It is still pumping 8 gpm. Adjusting between no nozzle and the proper 8 gpm nozzle that produces 3500 will get you where you want to go. Tell Russ Johnson what you are trying to do and he will sell you the right nozzles.
 
The gallons per minute will be determined by pump speed. So get the right rpm and then pick the tip for the psi wanted - within the horsepower of engine. GPM x Pressure / 1100 is approximately the horse power needed, 8 at 1300 is no problem. If you already have 8 gal then just use a bigger tip
 
Mike, a #14 tip will net you 1300 psi at 8 gpm.
 
That I do know (larger nozzle), but if I wanted to avoid the pressure spike to 3000psi that occurs with the unloader set for the higher range, how can I do that??....... I should have noted the nozzle size for that as I currently do that...... i forgot that....my bad.
Thanks so far for the help, Mike.
 
Do you have a pressure gauge on the line? Start spraying with the larger tip and crank it down down until the needle just starts to drop then go back up a tiny bit.
 
tomtucson said:
Do you have a pressure gauge on the line? Start spraying with the larger tip and crank it down down until the needle just starts to drop then go back up a tiny bit.
Click to expand...

Yes, I do have a guage on the line... my question is that when I run a 4015 nozzle and do not want the high psi spike, am I cutting my 8gpm flow back by turning the unloader down. If I am, how do I avoid that??? Is it possible?? and, If not what is an alternative to make sure 8gpm at 1300 psi with no pressure spike over say 1500psi??
 
Adjusting "working-pressure"..

EVERYBODY needs to know..
the unloader adjusts the spike-pressure..
the "working-pressure" is a side-effect of that..
to adjust the system for 1300psi "working pressure"..
you are going to find out how "sticky" your valve is,
by releasing the gun, and watching the "spike-pressure" or "trapped pressure"
..depending on whether your gauge is mounted before, or after the unloader..
If the gun is open, and the pressure is running 1300psi,
then you let go the gun, and spike jumps to over 1800psi.. replace that unloader.

for more.. jump-thread here
 
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