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  1. #1
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    Default Pump discharge pressure

    Hi guys need an answer on a question I had problems with, thanks Greg


    If friction loss on (1) 200 ft. 1 1/2 pre connect with 95gpm fog nozzle is 43psi, what should the Pump discharge pressure be for (2) 200 feet 1 1/2 pre connects flowing 95gpm fog nozzles?


  2. #2
    Forum Member IronsMan53's Avatar
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    43psi friction loss... It is exactly the same as for the single line.

    So if you had 100 psi fog nozzles then your PDP would be 143 for both situations that you presented.
    Last edited by IronsMan53; 03-09-2006 at 07:37 PM.
    I can't believe they actually pay me to do this!!!

    One friend noted yesterday that a fire officer only carries a flashlight, sometimes prompting grumbling from firefighters who have to lug tools and hoses.
    "The old saying is you never know how heavy that flashlight can become," the friend said.
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    So the total PDP for the whole situaltion is 143 right

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    Forum Member IronsMan53's Avatar
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    Yup, 143psi
    I can't believe they actually pay me to do this!!!

    One friend noted yesterday that a fire officer only carries a flashlight, sometimes prompting grumbling from firefighters who have to lug tools and hoses.
    "The old saying is you never know how heavy that flashlight can become," the friend said.
    -from a tragic story posted on firefighterclosecalls.com

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    Thanks Ironsman

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    Forum Member Dave1983's Avatar
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    Default

    Quote Originally Posted by IronsMan53
    43psi friction loss... It is exactly the same as for the single line.

    So if you had 100 psi fog nozzles then your PDP would be 143 for both situations that you presented.


    BINGO! 1 line or 5 lines, EP is still the same. The only thing that changes is your intake residual as you open more lines.
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    You might want to flow test your engine. You need to find out how much friction loss you have from the line going from your pump to where you connect at the swivel(where you connect your preconnect). Then add that to your friction loss and nozzle pressure.

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    Of course this is all subject to change if you go down under, in which case you'll have suction gain and you'll need to talk to Kiwi to figure the rest out. LOL
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    Make life easy for yourself..... Set a standard pump pressure of 150 PSI for your attack lines. Will make life a lot easier for your pump operators and training officers.

    The department I was with in VT had 200' 1.75" a 250' 2.5" attack line as our normal attack lines, and used that as a standard pump pressure. Pump operators were trained to add 20 psi for each 100' of 1.75" over the standard 200' pull (we kept 400' of 1.75 on each reel so that was not uncommon). The 150 PSI number is also handy because it works for sprinkler and stamdpipe systems as well.

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    LaFireEducator

    While I agree with setting a PDP, why not take the extra time and find out the correct pressure for each preconnect and mark the guage, instead of setting one pressure for all the lines and hoping that you get enough water.

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    I like the K.I.S.S. method!!! That's why we go with a standard 150 psi!!!! You can always adjust up or down accordingly....but it gives you a good starting point!!

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    Cool How it comes up here.........

    We use CQ2L...........
    The Coefficient for 1.5 =s 24.
    The Quantity is 95/100 or .95
    The Length is 200'/100 or 2.

    So the equation would look like this:
    24 X .95 X.95 X 2............. or 24 X .9025 X 2
    =s 43.......

    Now the way I understand it is that once this line is flowin' you can slowly open the other line and the pressure of the line that is already flowin' will decrease some as the discharge valve is being opened, slowly open the discharge and make small adjustments to the throttle to maintain the appropriate Pump Discharge Pressure of your initial line, remember to look at the Discharge Pressure Gauges and not just the Pump Pressure Gauge (Centrifugal Pumps are capable of using incoming pressure to increase the pressure generated by the pump and there may be a difference in the pressure coming into the pump and your Engine Pressure). As the second line is flowin' water adjust the throttle as needed, usually throttling-up is needed. Once both lines are flowin' at the desired pressures mark all of your gauges that you are using....... including Oil Pressure, Pump Discharge Gauge, Water Temp Gauge, Compound Gauge, R.P.M. Gauge, Discharge Pressure Gauge, Ammeter/Voltmeter Gauge, I hope you get the picture...... and as long as you have a steady water supply you' re on autopilot for the most part. I always recommend markin' all the Gauges because, that and the sound of the Engine and Pump should be the first indicators that something is goin' wrong.

    Notice that I did not mention anything about the Pressure Relief Valve..... set it in accordance with your Departments Policies/Procedures/Guidlines. I set mine once my first line is in service everytime, and I adjust it as needed.

    Well, best of luck to ya....... and stay safe.
    "Be LOUD, Be PROUD..... It just might save your can someday when goin' through an intersection!!!!!"

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    Cool Just had another thought.......

    Also just to say that the EP (Engine Pressure) is 143 is not totally accurate, even for a fog nozzle............
    Have we taken into consideration the low pressure fog nozzles that are operated at a nozzle pressure of 75 p.s.i.? So for that it would be 75 + 43 =s 118. The Engine Pressure is goin' to be based on the manufactures' nozzle pressure, I would also recommend you read the paperwork that came with the nozzle or check out the manufacturers website for the appropriate numbers..... An example is I believe an Akron adjustable nozzle is 90/95 p.s.i., a low pressure T.F.T. is 75 p.s.i. and the non-low pressure T.F.T.s are 100.

    Just wanted to get dat out there........ some food for thought.
    "Be LOUD, Be PROUD..... It just might save your can someday when goin' through an intersection!!!!!"

    Life on the Truck (Quint) is good.....

    Eat til you're sleepy..... Sleep til you're hungry..... And repeat.....

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    Are you talking about supplying the 2 lines through the same discharge? If so you will have to account for the device that you are using (probrably a gated Y) and that adds 10 psi(as a rule of thumb).

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    Our commander setting is 150psi, too, though on 200' of 1 3/4 we pump 170psi.


    10 psi under 350 gpm, over it's 25psi (for us)

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    My department has a standard GPM for interior attack, not a standard PSI to automatically throttle too. Our standard GPM is a minimum of 150 GPM for a handline on interior attack. Your PSI will depend on how long the line is. Take the time to calculate things correctly and give your brothers on the other end the proper amount of water and pressure. If you know what you're doing, it doesn't take long. And don't simply add an amount for each section of hose because the friction loss depends on your GPM - you can't simply standardize.

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    You can standardize if you have preconnects. The pressure gives the flow expected. That 170 translates to 150 gpm for the lines with the Akron and about 170 gpm for the line with the tft. That's why we pump those preset pressures--because of the gpm.

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