1. #1
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    Arrow 2.5 inch discharge

    I am trying to find out what is the maximum GPMs that you can get out of a 2.5" discharge on a 1000gpm pumper supplied from a good hydrant. The reason I am asking this is we are trying to figure out whether it would be better to supply another engine connecting their 5" hose to the 2.5" discharge with an adapter. The other option would be using two 3" lines coming off the pump connected to a siamese adapter to the 5". We do not have a large diameter discharge on our engine, just the 2.5" discharge with the 5" adapter.

    Thanks,
    47
    Last edited by Eng47ine; 05-03-2004 at 10:14 PM.
    Thanks, Nathan

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    Default 2.5 discharge

    To accurately give you the correct numbers you would need to supply more info than that. Such as intake pressure. A good hydrant leaves a lot to the imagination. I can tell you from my testing on a 1000 gpm pumper that with a "good" hydrant, a relatively straight discharge run from the pump and the wind in the right direction a 2.5 discharge can and will do 1000 gpm without issue. We have an older Seagrave without a large discharge and can supply our aerial using a short 5" LDH run at 1000 gpm. So the bottom line is yes - but proper testing would be the only way I would trust that it is. Maybe time to bust out the old pitot gauge and give it a go....

    Chief Kuhl
    Waterloo FD

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    Default

    You seem to be asking 2 questions:

    1) What flow rate can be achieved?
    2) Which is the better arrangement for the discharge:
    A) One 2-1/2" X 5" connection, or
    B) Two 2-1/2" X 3" connections to a siamese and then 5" hose.

    1) As indicated by chiefwaterloofd, a “”GOOD” hydrant is indeed relative. The flow rate is as much, or more, dependent on the diameter and length of hose from the hydrant to the pump suction.

    For example, consider a hydrant having the following data at the hydrant discharge:
    Static Pressure = 110 psi
    Residual Pressure = 90 psi at 2,000 gpm
    (This should be considered a “GOOD” hydrant by any definition.)

    Now, if you are using 50 feet of 2-1/2" hose, you can expect approximately 910 gpm at the pump with 20 psi residual pressure on the compound gauge.

    If you are using 50 feet of 5" hose you can expect approximately 3,280 gpm at the pump with 20 psi residual pressure on the compound gauge.

    2) To analyze the hose arrangement on the discharge, you must consider the pressure loss in the two arrangements between the 2-1/2" discharge outlet and the 5" hose inlet.

    In Option “A”, the pressure loss is in the sudden expansion from a 2-1/2" diameter pipe to a 5" diameter hose (4.5" +/- actual dia). This depends on the shape of the adapter. Assuming a worst case scenario where the expansion is “sharp”, the pressure loss is approximately 14.4-16.4 psi at 1,000 gpm.

    In Option “B”, the pressure loss is the sum of
    (1) the loss in the sudden expansion from 2-1/2" to 3",
    (2) the loss in the 3" hose,
    (3) the loss in the sudden contraction at the siamese, and
    (4) the loss in the siamese.
    Assuming you are using a 20 ft section of 3" hose, the losses are:
    1.15 psi - sudden expansion (500 gpm)
    1.3 psi - sudden contraction at the siamese (500 gpm)
    4 psi - 20 ft of 3" hose (500 gpm for 2 hoses)
    10 psi - siamese (this is more of a guess as I have seen a lot of numbers for this value.)

    The total pressure loss is approximately 16.5 psi at 1,000 gpm. This makes it about a wash. It depends a lot on the loss in the siamese and the length of the 3" hose.

    As always in these matters it is best to conduct an actual field test. If it is indeed a wash, you then must consider the increase in setup time of Option “B” over Option “A” as well as the cost of both options.
    Last edited by FireH2O; 05-04-2004 at 05:23 PM.

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    Default

    When it comes to moving water, it is always advisable to use the K.I.S.S. PRINCIPLE (KEEP IT SIMPLE STUPID) Using this the 21/2X 5 would be the way to go. As pointed out above, you have to consider the setup time for the required layout.

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    Default

    Well, one thing to keep in mind is that a 2 1/2" open pipe is what is used to pump test 1750 and 2000 gpm trucks. You should be able to get a minimum of 1000 gpm, probably closer to 1250 gpm if running out of a hydrant. Traditionally, the best discharge on a pump is the front officer's side discharge. If you run off that discharge, you should be pretty well set to run the 5" right off that discharge. I would say that the friction loss calculation through the (2) 3" lines into a siamese is a little light. The flow into the 5" directly is the way to go. Plus, its a lot easier to setup that way.

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    A single 2-1/2" outlet to test 1750 and 2000 gpm trucks?

    Hmmm when we tested ours we had (4)2-1/2" lines connected to the truck with two pipes being fed by two lines with dual gauges.


    I would go with the 2-1/2" straight into the 5" adapter.

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    Default

    2.5" to the 5" is the way to go...None of our trucks have the LDH discharges, we use 2.5" to 4" and go from there.

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    FireH2O


    HOLY MONKEY!!!! im guessin that you deffinitly took some pump classes and took some serious notes! WHew... thats kick azz if that is all from your head and not from a book dude really. we still go with the "what? need more" turn it up a notch. i can remember my pump class and oh boy did alot of us have trouble keeping our traps shut behind friction loss when were very rural.

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    dwwm2c4, would you believe my first or second pump class was at the Mercer County Fire School (down the road from you in Hermitage)? I did a lot of camping and fishing at Pymatuning, too.

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    As said before the K.I.S.S. method reall applies here.
    Just put an adapter on the discharge and call it good.


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    Originally posted by FireH2O
    dwwm2c4, would you believe my first or second pump class was at the Mercer County Fire School (down the road from you in Hermitage)? I did a lot of camping and fishing at Pymatuning, too.

    Oh i believe you! yea im about 20 mins from Pyma and ive ever attended the Mercer co. fire school...only the Crawford/Venango fire school in which is getting pretty bad

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    Default

    Regretably in this modern world of large pumps and larger egos,the art of fire hydraulics is becoming a lost art.One of my drivers,when queried about the proper pump pressure for an evolution,made the unfortunate comment made by one of the other posters;"I don't know,if they not getting enough just turn it up a notch".Un Huh,WRONG ANSWER! Do you like your new found position of Driver/operator? Yes. Were you TRAINED how to do this job? YES. Well GUESS WHAT! You have one minuter to supply me with the proper pressure for this evolution or you'll be doing remedial friction loss training for the remainder of the month."I'm going to talk to Tommy"(the Chief).Errrh,Boy what does it say on my helmet(DC/Safety)? Do you think that's a real good career move? Amazingly after a few seconds of soul searching he managed to come up with the F/L close enough so he wasn't going to kill anyone.And the chat with the chief led him right back to the get it right or you're going back to class.The Boss has a real low tolerance for paying good money for schooling and then having the troops not using what they've learned.Gotta love support when you're in my position.You're going to run the pump you better know how to at least crudely estimate F/L. T.C.

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