Thread: friction loss

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    Default friction loss

    I'm trying to remember the friction loss in psi. for 1.75" and 2.5" line. also pressure loss per floor. I knew this a long time ago but my mind isin't what it once was. The operators in my department have become lever pullers and I want to teach them the math.

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    Hi rambus112,

    According to a "wallet card" I have, 1.75" hose with 1.5" couplings is as follows, based on 100' lengths of hose:

    Flowing Loss
    95 gpm 14 psi
    125 gpm 24 psi
    150 gpm 35 psi
    175 gpm 47 psi
    200 gpm 62 psi

    2.5 " hose, per 100' lengths

    Flowing Loss
    175 gpm 8 psi
    200 gpm 8 psi
    225 gpm 10 psi
    250 gpm 13 psi
    275 gpm 15 psi
    300 gpm 18 psi
    325 gpm 22 psi
    350 gpm 25 psi

    It is 5 psi of friction loss per story, wye or siamese.

    Just as an FYI, if you are were flowing CAFS thru the same lines, friction loss would "0" for all of the above.

    Hope this helps,

    Captain Lou
    "GotFoam?"

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    I believe it is an increase of 5 psi per 10 ft of elevation and a decrease of 5 psi per 10 ft below grade level. Also, friction loss varies by hose manufacturer so you might check their website.
    Tom

    Never Forget 9-11-2001

    Stay safe out there!

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    Friction loss in hose and appliances varies by their construction. The only way to know for sure is by testing with flowmeters or pitot tubes. Most of the charts I've seen are based on either a specific hose or are based on the old stuff.

    For example, a chart from 1975 may show FL for 1 3/4" hose as 50psi/100' at 180gpm. You may test a new length of hose that, due to modern materials and construction, will only be 30psi/100' at 180gpm.

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    The FL=CQ2L method is popular for figuring friction loss.
    FL= friction loss per hundred foot
    C= coefficient
    Q= quanity of water in hundred of gpm
    L= length of hose in hundred of feet
    Coefficient of 1 3/4" hose is 15.5, for 2 1/2" its 2. An 1 3/4" hose 200 ft long flowing 180 gpm would work out like this: FL= 15.5 x 1.8 x 1.8 x 2. Would be 100.44 lbs of loss. if i did the math right.

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    Quote Originally Posted by grizzlytooth
    i found this post funny. i remember the formula, but honestly, in my city there are the rules and there is the way we really do things. 1 1/2 inch line or 1 3/4 inch line, add 10 psi for every 50 feet, and 10 psi for every floor up. 2 1/2 ich line add 8 psi for every 50 feet. and who cares about gallons/minute. do our method and all is well. the only rule we follow is less water out than in, don't cavitate the pump and life is good. all that fancy math is for inexperience. do you really want to wip out the calculater in an emergency at 0400 hrs in the snow.
    YIKES.

    Underpump a line, and find out what happens when the crew is getting burnt alive. Hydraulics isn't just for the "inexperienced fools".
    Quote Originally Posted by ThNozzleMan
    Why? Because we are firemen. We are decent human beings. We would be compelled by the overwhelming impulse to save an innocent child from a tragic, painful death because in the end, we are MEN.

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    No, you don't whip out the pencil and calculator on the fireground.

    You whip them out when you're doing your pre-plans.

    You whip them out when you're reviewing your SOPs and want to make sure you have the right combination of hose diameter and pump pressure to feed the nozzle you've put on the end of the preconnect.

    You whip them out when you're at drills or doing annual hose testing to verify you're achieving the GPM that math says you should. If you're significantly less, and you've double checked your math, you start looking for maintenance issues whether it's a clogged fog nozzle, hose whose lining has delaminated, or something ****ed up on your pump or guages.

    You whip em out to show somebody why the 1.75" line with 100psi fog nozzle ain't a good idea to use off the standpipe.

    You whip em out when you've received bids back on fire hose, and need to compare the relative quality of the lines (along with stuff like weight, bending radius, etc).

    BTW, go with the manufacturer's friction loss specs all the time.

    Most of the "formulas" and "tables" you see in the IFSTA and other books are based on hose from 40 years ago. They are accurate for rubber lined, double jacketed cotton fire hose or whatever the table says it's for.

    Modern fire hose usually has slipperier lining materials like polyurethanes instead of rubber; they may have the liner impregnated into the inner jacket altering the interior size larger than the nominal hose size, and the hose jackets may be more flexible and expand when pressurized to larger than nominal.

    Angus Hi-Vol is one well known example -- it's 4" and 5" both gain 2/10ths of an inch when charged, and 2/10ths is a huge difference in this application.

    Ponn Conquest is a nice attack line that combines the slipperier polyurethane liner, embeds it as part of the inner liner instead of a seperate layer, and according to some also expands under pressure -- whatever they do, the net effect of everything is their 1.75" performs like most mid-price range 2".

    So yep, on the fireground, you can use the system of when the firemen lift off the ground, turn the throttle to the left method.

    But there is an awful lot of planning & engineering you should be doing off the fireground that a solid understanding of hydraulics and fire hose construction is very important. Because getting that stuff right helps reduce problems the night of the big one.

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    We have our preconnects engine pressures posted in the engineers compartment for a quick reference. If we have a more complex hoselay, I will pull out the calculator in a minute if i need to. Having the proper pressure everytime is the mark of a true Engineer.

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    "all that fancy math is for inexperience."

    All good engineers understand the need for friction loss and how it fits into the whole scheme of things and it is not a seperate entity at the fire but works along with everything else to put the fire out.

    Learn it and use to help keep from burning things down.

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    Quote Originally Posted by grizzlytooth
    i found this post funny. i remember the formula, but honestly, in my city there are the rules and there is the way we really do things. 1 1/2 inch line or 1 3/4 inch line, add 10 psi for every 50 feet, and 10 psi for every floor up. 2 1/2 ich line add 8 psi for every 50 feet. and who cares about gallons/minute. do our method and all is well. the only rule we follow is less water out than in, don't cavitate the pump and life is good. all that fancy math is for inexperience. do you really want to wip out the calculater in an emergency at 0400 hrs in the snow.


    brakes, neutral, pump, drive, line out, drop the tank, charge the line, hydrant to panel, reduce rpm, open line, increase rpm to proper psi, close tank, fill tank, monitor pressure and pump temp. that's it.
    WOW!! I suppose as long as nothing ever changes, and no additional line is needed, and you don't care if the line is under or overpumped, your system works great.

    We expect a little more than being lever pullers out of our pump operators. We expect them to be able to think, to adapt to the situation and for damn sure make sure the right PSI and flow are making it to the nozzle.

    I think it is a shame that people don't believe knowing the right way to do your job is relevant anymore.

    FyredUp
    Last edited by FyredUp; 03-04-2006 at 02:49 AM.

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    Quote Originally Posted by FyredUp
    I think it is a shame that people don't believe knowing the right way to do your job is relevant anymore.
    Oh jeez......you know that brains and people who can think on their own don't belong on the fireground. We all need to be mindless robots...duh..
    FF/NREMT-B

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    Courage is not the absence of fear, but rather the ability to control it.

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    We don't have dedicated positions in my city. You can be a driver of a pump or a ladder one night, hydrant man the next, or first in on a line the next. My question is, having known all the formulas and given the guy on the line has an adjustable gallonage nozzle. What if I don't know what he has it on, then what? We just guess, or better yet for a 1 1/2, we will assume 10 psi per 50 feet. Is there another, proper way because I don't drive that much? I read that grizzlytooth guys thing and although it was a bit rough, he had a point about too much math on a fireground.

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    Thumbs down

    grizzlytooth must be one of those guys that, when asked how much pressure should be on the line, says that all he needs is for the nozzleman to do this:
    Attached Images Attached Images   

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    Don't laugh, we don't use a thumbs up or thumbs down, but my department communicates by portable radio. Everyone has their own and you would get 100 psi plus friction loss. If you wanted more, you would have to tell me by radio.

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    I would say that a hose chart would be the best thing for your department to create. But it isn't as easy as just copying numbers from a book.
    For 2 1/2" hose the 2Q^2+Q has been a standard for many years. You wouldn't be wrong to copy the numbers but if you test the hose you can create your own chart.
    IFSTA is a fine reference for the numbers you need without testing.
    Instructions for testing your own hose is also inside the IFSTA books.
    You may find that by testing that your numbers are different enough to want you to change.
    Every driver needs a good working knowledge of friction loss, the thumb up and thumb down is not acceptable.
    In the math world friction loss is an Exponential function and given the actual numbers anyone who has had college level algebra should be able to spit out an equation like the 2 1/2" (2Q^2+Q)
    Once you get into it you may see some problems, for years IFSTA and others have changed how we calculate 1 3/4" hosefor some time it was the CQ^2+Q then 10Q^2, then 10Q^2+Q and I have also seen 10Q^2+10. All of which give you slightly different numbers.
    Enough to feel on a hose line, NO. but in some strange leadout configuration it could make a difference.
    Anyway, I hope that helped more then it confused you. It is important to have real numbers. If you have the ability test your stuff. Otherwise IFSTA will get you close. http://www.ifsta.org/html/catalog/36...41764846.25073

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    Oh, one more note. Once you get the proper pressures, let your attack crews feel what the proper pressure is like. I know many firefighters who never knew that 181 gpm felt like that

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    Thanks for the info. So many departments have lever pullers and not enginers. I've even seen paid departments with lines painted on their discharge gauges. All some guys know is pull these 2 levers and throttle up until the needle touches the line. If they ever get a major fire where they have to supply multiple handlines of different sizes they and the guys on the line are screwed.

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    Lightbulb Pump Chart

    We use a pump chart. Here's a link HFD Pump Chart . I just spent a good chunk of time calculating and designing this chart. Every size hose was pumped and measured at multiple lengths and multiple gallonages. We used flow meters and pitots. The coefficients are listed near the appropriate chart. All of our aerials and master stream appliances where also flowed and measured. I designed Excel spread sheets that calculate everything from Friction loss and coefficients to nozzle flow and nozzle reaction.
    A lot of people may see this as a big waste of time. I think it's a great way to get to know your equipments capabilities. We found that there was more than 20% less friction loss in our 1 3/4 hose. Our last pump chart was made in the early 90s. Hose has obviously changed a little bit.
    The pump chart is an easy way to calculate pressures and flows @ 4 am. We still teach our engineers how to get to these #s using the math.

    Live like your going to die tomorrow and learn like youre going to live forever.

    Corey

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    Talking Friciton loss calcs........

    I agree with checking the Manufacture' s specs. However, at 0200 in the morning I don' t wanna be thinkin' O.K. what hose manufacture are we using? My Department uses CQ2L like described before, for our Manufactures this is right on......... confirmed through our hose testing.
    I have a cheat sheet that I made-up, with all of my friction losses on them; it starts at 30 gpm and increases to 50 gpm, the after 50 gpm it increases by 50 gpm.
    I came up with this because I like to work smarter, not harder. It starts at 30 gpm because that is the minimum flow on one of our nozzles; it is increased to 50 and then increased by 50 gpm because that is what our adjustable nozzles range is. For our automatic nozzles, I use the same formula, because the F.F. is the one that is actually controlling the gpm being flowed, by how open or closed the bale is.
    As for friction loss of elevation I use .5# per foot of elevation, after the first floor. The equation for this would look like this: Number of floors - 1, then that number is multiplied by 5 (residential) 6 (commercial) and 10 (industrial). This works for our Department, but through pre-planning I know that I have 10' residential floors, 12' commercial floors and 20' industrial floors.
    Friction loss in appliances is like this: 10 =s Y's and Siamese, 15 =s Ladder pipes and Standpipes and 25 for all Master Stream appliances.
    Hope this helps. Sorry that others in higher positions were not able to educate you. Remember that just because you were promoted, doesn' t mean that you shouldn' t remember the basics.





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