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Pumping scenario / brain teaser.......

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  • Pumping scenario / brain teaser.......

    Here’s a pumping scenario:
    You are coming off of a domestic hydrant at 1450gpm with 300 feet of 5 inch hose. The hose is connected to the pumper with a 6 inch connection and there is no pressure relief valve. The pump is set to work in pressure mode at 150psi. The pump is rated at 1250gpm. The engine is pumping out a 2 ½ inch discharge into 200 feet of 5 inch hose. After the first 100 feet there is a 5 inch gated wye (only using one half of the gate) then the additional 100 feet to another hydrant. The purpose of this hydrant is to feed an industrial site fire loop. The pressure on the fire loop is approx. 130psi.

    1. What gpm would you be flowing out of the pumper?
    2. What would the gpm be going into the industrial hydrant?
    3. What would be the gpm in volume mode at the same pressures?
    4. What would be some recommendations to get at least 800 gpm at
    the industrial hydrant with this setup?
    5. Would it be better to use 2 sections of 2 ½ hose rather than
    a 5 inch line or use 2 five inch lines coming off of 2 ½

  • #2
    If you know your domestic hydrant is giving you 1450 GPM you have the answer to #1 and #2, flow should be constant. If you just know that's what its capable of, you need more information

    If your discharge pressure into 200' of 5" is 150 psi, you could expect roughly 115 psi at the industrial hydrant depending on the friction loss in the gated wye (depending on type, could be 25 psi).

    Why is the pumper in pressure mode rather than volume?

    What is the purpose of the gated wye?

    Using two 2 1/2" lines changes your friction loss coefficient from .08 to .2, your friction loss practically triples. The 5" is always more efficient at this flow.

    I would pump in volume and use the same setup minus the gated wye unless there is some other function for it I'm not aware of. To deliver 800 GPM @ 130 psi you need a pump pressure of roughly 140 psi when using 2 lengths of 5" with no gated wye.


    • #3
      What on Earth??...................

      I'm totally confused on this one: 1. Why isn't the pumper ON the hydrant? What is the residual pressure at 1,450gpm? What is the static pressure on the hydrant? We don't Own, Like, or Use LDH, I'd give you 1,[email protected] 140psig at 700ft distance with the pumper on the hydrant, delivering water thru 3 3in lines. Re: the pump itself, we have all single stage pumps, and have had since 1971. Stay Safe....
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      • #4

        Interesting set up, I'll assume you threw the wye in for additional FL! Theres alot of questions, but not enough info on set up.
        hwood is right a static psi would be nice, but you say it supplies 1450gpm. It will take 30 psi to get the 1450gpm through 300' of 5" to the engine, assuming theres enough hydrant psi to move it.


        1. gpm from pumper: With the 300' set up and no static or residual psi I'd say you'd be lucky to discharge between 1000-1250gpm.

        2. gpm to ind. hydrant: 150psi on master gauge will net you around 100psi from a single 2 1/2" discharge at 1250gpm. You can move that 1250 with no problem, 14psi FL for the hose and you can add 25psi FL for the wye. So that leaves you 60psi which has to overcome the 130psi of the ind. hydrant.

        3. volume mode: I'll leave this one alone. It's all about psi!

        4. Reccommendations to 800gpm: scrap that set up. Hook to hydrant with 2 or more LDH pony lines and use 500' of 5" to the other hydrant. You can pump LDH "supply line" up to 185psi this will allow you to overcome the 130psi at the ind. hydrant.

        5. two 2 1/2" or two 5": Think you're talking about hydrant connection here. If so, don't go backwards. Forget the 2 1/2"! Use 5" or 6" pony lines. It doesnt matter how strong a hydrant is, your only as good as your set up!

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