1. #1
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    Default Another Phun Phire Ground Fysics Question for ya all..

    A while back a had a question for you all about our new 4 inch plum(b)ping on our tanker/tender. I got some great responses. Well, now I have another question for you, this time, also concerning flow rates and whatnot.

    Here goes:

    Our department’s Engine (Engine 1) has a 1050 pump, obviously with both 3inch and 6inch hard suction ports. Nine times out of ten the 3inch hard suction is our mainstay option for drafting operations (usually just filling the tank after practicecs/calls). However, we all know the saying that a bigger fire needs bigger water, which is where the 6inch comes in handy. We’ve got a pretty strong pump on our truck (last pump test, overload capacity actually showed it pumping just shy of 1200gpm). Now, at any drafting operations it is always wise to use a strainer on the end of your HS. Right now, we have a regular strainer of the non-floating kind. Our old truck had 4 ½inch hard suction (650 pump), when it was sold to a farm up island, the new owner didn’t want the 4 ½ inch stuff, so we hung onto it. I have been doing some checking around, and a 6inch floating strainer is going to set us back at least $1K, where as the fittings to ‘adapt’ the 4 ½ inch floating strainer would only cost us about $200.00. We don’t have a problem spending the money, but if we can save money, we’re all for that as well.

    What my question, and concern is, that if we get the adapters for the 4 ½ inch floating strainer so it can be used with the 6 inch hard suction, are we going to be restricting the maximum capacity of the pump? Will the reduction still supply the pump with enough water to move 1050gpm, or more? Or would the reduction be negligible?

    My other questions is, are drafting flow rates (if there are such thing) calculated the same as pumping flow rates?

    Like always, the more detail an explanation you can give would be greatly appreciated.
    Last edited by firefighter26; 04-01-2003 at 12:56 PM.
    "No one ever called the Fire Department for doing something smart..."

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    Default

    Just cuz I had nothing to do last night, I figured I would try to 'draw' it out (which always helped me with physics problems).

    On a side note, Malahat Two-7 has made a quest appearance as the pump operator. (and yes, you are on the right side of the truck.. For the purpose of this drawing, the 6inch is coming from the passenger side)

    "No one ever called the Fire Department for doing something smart..."

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    Hee hee...sorry 26, I missed the question after you referred to the "plumping" on your truck. Our trucks are very fit and lean **giggle**

    Also, Malahat is shorter than I imagined...

    Now, back to feigning seriousness. I would think that the little tiny holes on your strainer would be numerous enough to be OK even with the upgrade. I say that because you have to figure that they would be designed to flow a fairly small volume of water per hole so that you would not get the whirlpool effect. This would be especially important with a floating strainer that would be more susceptible to losing prime.

    I have no physics-based proof of this. It's all from the mind of me. As such, consider it dangerous.
    "Be polite, be professional, but have a plan to kill everybody you meet.”
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    hmmmm.... I never considered the tiny hole factor....
    "No one ever called the Fire Department for doing something smart..."

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    Non-scientific guesstimate: You'll get the 1050gpm rated capacity out of the 4.5" strainer. Only way to know for sure is to actually try it.

    The suction side of the pump does benefit from things like bigger suctions & dual suctions -- our 1500gpm engine does 1400gpm through it's front mount suction alone, dual suctions (one front, one from the passenger side steamer) brings it up to 1800gpm.

    Centrifugal fire apparatus pumps are rated for their capacity at 150psi discharge from draft and/or 150psi net pump discharge. So a 1050gpm (darn Canadians and their Imperial measures...or is a blooming liters thing!) pump will put out 1050gpm @ 150psi from a 10' draft with the appropriate size suction (which I can't remember off the top of my head )

    From a positive supply, like a hydrant, it's 150psi net -- if you have 1050gpm @ 30psi coming in, you can discharge 1050gpm @ 180psi.

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    26,

    From experience by testing, the 4.5" with adapters will impede the flow. You might get close to capacity but at a much higher RPM.
    My suggestion would be a "KOCHEK Brand" lightweight floating strainer. About $700 if I remember . You will not be disappointed.

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    Originally posted by Dalmatian90
    darn Canadians and their Imperial measures...or is a blooming liters thing
    Dal, you mean to say that kilopascals, Imperial Gallons, Litres, and Millilitres don't make any sense to you

    To be honest, 9.9 times out of 10, we stick with GPM, PSI, and Inches. (we've got combination gauges that show both )
    "No one ever called the Fire Department for doing something smart..."

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    Lightbulb Try before you buy!!!!

    26,

    I have to agree with wtrboy, The 4.5" fittings and strainer will most likely restrict the flow. The degree of restriction will be dependent on the size and design of the strainer. Only by conducting a flow test will you be able to determine the degree of restriction and decide for yourself whether the additional GPM is worth the $$$ outlay. My guess is that you will see a significant loss in GPM.

    If you choose to use adapters on a floating strainer, Keep in mind that adapters mean more connections to leak and further decrease the flow.

    My recommendation would be to talk to your local distributor and get the strainer you want to test before you lay out the $$. Even strainers sold for a 6" intake will vary in flow capacity from brand to brand. We received a "Brand X" barrel strainer when we bought our last new engine. The engine is a 1250 GPM with a 300 hp Series 40. With the strainer, we got somewhere about 900 GPM. When we changed to another type of strainer, we flowed close to 1500 GPM. Needless to say, The barrel strainer is now used as a doorstop in our junk room.

    Both of our engines are equipped with ZICO floating strainers and low level strainers for folding tank use in addition to standard barrel strainers. We have been happy with their performance but you should try a few types and decide what works best for you. I have used the KOCHEK brand with no complaints.

    Don't let the salesmen do your homework for you. Get it, Flow it, and buy the one that works best for you.

    Good luck,

    Jim

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