Thread: Flows and Friction Loss
07-21-1999, 02:29 PM #1e33Firehouse.com Guest
Flows and Friction Loss
We have the following lines on our engine:
(2) 200' 1.75" with Akron Turbojets. It is standard Ponn double jacket fire hose. Nozzle selections are 30-60-95-125.
(1) 200' 3" With Akron Turbojet 150-175-200-250 (I think). Same hose type.
What pump pressure is needed to get the flow from the nozzle and what is the friction loss? Ill be damned if i can find a friction loss chart to look at.
I'm not interested in knowing how lacking and insufficient this set up is, i know its pretty sad for a hose compliment...save the critisism for another day please..all i want to know is what the pump pressures need to be to get the selected nozz;e gallonage. Thanks for any help.
07-21-1999, 06:48 PM #2K AFirehouse.com Guest
---We have the following lines on our engine:
(2) 200' 1.75" with Akron Turbojets. It is standard Ponn double jacket fire hose. Nozzle selections are 30-60-95-125.----
Sounds like over kill on the hose, 1 1/2" would be a better choice. Pump 103, 111, 128, or 148 psi. depending upon the setting of the ring on the nozzle. You could run a 1 3/4" line at max flow out to 850 feet.
---(1) 200' 3" With Akron Turbojet 150-175-200-250 (I think). Same hose type.---
Once again the hose is way too large for the flows expected, you are simply dragging a bigger heavier line for the flows out of a 3 inch that could be achieved froma 1 3/4" line. Pump 103, 104, 105, or 108 psi. YOu could run a 3 inch line at max flow 5,000 feet.
-- what is the friction loss?---
1.5, 5.5, 14, and 24 psi for the1 3/4" and 1.5 2, 2.5 and 4 psi per 100 for the 3"
A 200 foot 1 3/4" line will achieve any of those flows through that length of line.
07-21-1999, 09:05 PM #3resqcaptFirehouse.com Guest
We use the friction loss formula from IFSTA Fire Streams book.
That formula is FL = C(Q2)L
FL = Friction Loss (duh!)
C = Coefficient (constant depending on size)
Q = GPM/100
1 3/4" = 15.5
3" = 0.8
Example: 200' 1 3/4", flowing 150 g.p.m.
FL = 15.5 (1.5)2 2
FL = 15.5 (2.25) 2
FL = 69.75
EP = 100 NP + 70 FL = 170 p.s.i.
This works for a formula. We've found the best way to find your engine pressure is to place an in-line guage at the nozzle, run your throttle up until you read 100 on your guage and mark that pump pressure. Do this for each nozzle setting. We've found some variance from truck to truck with plumbing, etc. Of course we have to place a "cheat" sheet so overtime Engineers know what to pump each truck which has caused some confusion. Oh well, I guess nothing's perfect in this here world.
[This message has been edited by resqcapt (edited July 22, 1999).]
07-21-1999, 09:42 PM #4Dalmation90Firehouse.com Guest
I have a spreadsheet made up with these calcs on it...if you can figure out how to use Excel, it's pretty good...one of these days I'll get around to putting a pretty face on it
goto http://pages.cthome.net/mortlake and then click on the FireInfo link for directions to download/use it.
07-24-1999, 05:33 PM #5BIG PAULIEFirehouse.com Guest
I've got a couple of suggestions. If all of your hose is from the same manufacturer, get the friction loss specs from them. They are usually pretty accurate. For any line that is pre-determined such as preconnects, Pitot the flows. Use smooth bore tips, obviously, try to match a tip with your required flow to as close as possible to the nozzle pressure that you will be using on that particular line. For example-if the nozzle to be used is a 100 psi automatic, use a tip size that will get the required flow as close as possible to the 100 psi. If again, for example, let's say your pitoted nozzle pressure is 80, just add the difference from 80 to 100 (20) and you will have the required engine pressure for that line.
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