I've done this a couple of times before - for GSA, no less.
Believe it or not, part of that dramatic pressure drop across that
valve IS friction loss.
The manuacturer will usually give you a loss table. In my case I
showed that loss (friction) in the appropriate
column and let the less be a fixed drop.
Hope this makes sense
At 05:03 PM 6/19/2012, you wrote:
I have an existing install that needs to be re-calculated due to
some modifications. The system has a booster pump and downstream of
the discharge, before the feed main disappears into the structure,
there is a pressure reducing valve which is sett to 150 psi. I would
like some confirmation that I'm calculating this thing right (hydracalc).
I've set up a couple of nodes for the PRV and for the first run I
set the friction loss at 0 to get an idea of what the discharge
pressure is at the point of the PRV. Then I basically go back and
enter in the difference of the pump net pressure and the PRV setting
of 150 psi as the fixed friction loss through the PRV's nodes. So
for example, let's say the pump is capable of 200 psi at my system
demand and the PRV is at 150 psi - I set the fixed friction loss at
the PRV to 50 psi to achieve the pressure reduction. Does this sound
about right?
This is more of a software question than anything I suppose but any
input is appreciated.
Thanks!
RB
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