Hydraulic equations

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Permalink Reply by Daniel Cook on January 28, 2009 at 9:31am

I would like to have a copy of your sheets if possbile as well. dcook82@verizon.net. Thanks.

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Permalink Reply by Michael Grcich on January 28, 2009 at 9:56am

Here is a power point presentation you may wish to view.
http://www.tft.com/newsite/literature/library/files/05fire%20ground...

If you contact the companies that manufacture the hose, nozzles and other water delivery applicances your department has in service they typcially are willing to supply you with the cards or slide charts that will have the information you are looking for.

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Permalink Reply by Bob Franklin on April 6, 2009 at 11:35pm

Hi Colin,

We developed a simple "rule of thumb" friction loss for our engineers. 1-1/2 hose is 30 psi per 100
1-3/4 hose is 20 psi per 100
2-1/2 hose is 10 psi per 100
3 hose is 5 psi per 100
All you have to add is your nozzle pressure and lenght of line and you are all set!
We use 50 psi nozzles for our 1-3/4. we carry 200 ft with nozzle, FL=40+ Np 50 = 90/100 Pump discharge pressure.
Some engineers have marked the gauges for normal pump ops, knowing if at the add a line they know how much to adjust the pump throttle.

Come visit me a "Let's Talk Pumps", FDIC, Thursday 1030-1215, Room 206-207
Hope this helps,
Bob Franklin

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Permalink Reply by Jason Gennaro on April 7, 2009 at 4:38pm

+1 on what this guy said.

If you really want to know what you're flowing you're going to have to get the flow meter and pitot gauge. Every fire apparatus has different bends, valves, and whatnot even if they're sister vehicles. The point here is even if you have the same exact trucks they'll flow different. The pitot and flow meter are you're best bet to get the correct pressures.

If you don't want to go that route due to financials or whatever get in touch with the hose, nozzle, and appliance vendors and get their data. It won't be the most accurate but it's better than the hand method or generic formulas. My opinion. Good luck bro.

Adam Miceli said:

I'd second running your own tests and developing your own cards. We've found that different hose and discharges have a significant difference in FL. We use the C Formulas as a baseline, but nothing beats a calibrated flow meter and pitot gauge to determine actual friction loss and preset gauges.

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Permalink Reply by Adam Miceli on April 8, 2009 at 7:34am

Bob Franklin said:

Hi Colin,
We developed a simple "rule of thumb" friction loss for our engineers. 1-1/2 hose is 30 psi per 100 1-3/4 hose is 20 psi per 100
2-1/2 hose is 10 psi per 100
3 hose is 5 psi per 100
All you have to add is your nozzle pressure and lenght of line and you are all set!
We use 50 psi nozzles for our 1-3/4. we carry 200 ft with nozzle, FL=40+ Np 50 = 90/100 Pump discharge pressure.
Some engineers have marked the gauges for normal pump ops, knowing if at the add a line they know how much to adjust the pump throttle.

Come visit me a "Let's Talk Pumps", FDIC, Thursday 1030-1215, Room 206-207
Hope this helps,
Bob Franklin

Bob, did you guys test your hose and pumps to validate your numbers? In particular the 1.75" FL you show as 20 psi by formula would be accurate at less than 125 gpm and the 3" FL at 5 psi is theoretically/mathematically correct for under 335 gpm both far less GPM than normally flowed through the respective hoses. Again, these number could very well be true given newer hose tends to be "oversize" in dia. and liners tend to create much less drag than older types. We've found a huge difference in our three types of 1.75" hose all between 35-72 psi FL @ 185 gpm per 100 ft.

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Permalink Reply by Keenan Mulvaney on April 9, 2009 at 12:01pm

Pump operators at the University Fire Department are trained to memorize a given set of GPM's, Frictions losses and operations and use a standard equation for hydraulic calculations. We train so that operators have a thorough understanding of field hydraulics and when they become certified on the apparatus they can choose to use cheat sheets. Most members will carry a dry erase marker, that helps with doing the equations.

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Permalink Reply by Joy Beth Moser on April 12, 2009 at 12:11am

Yep, as Mulvaney said, at UFD we learned to use GPM to calculate the exact theoretical friction loss per 100 feet of hose. It takes good math skills and the ability to think on your feet. You were required to have the exact answer to any hose lay or standpipe problem by the time you caught your own hydrant as the guys on 2 preconnects tried to run you out of water. I still take pride in my ability to calculate exact theoretical engine pressure on a busy fireground and use UFD hydraulics as a pump operator at my current job. I prefer to be able to justify every psi I pump rather than use "rules of thumb".

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