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  1. #1
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    Default Different Stage Pumps

    Im curious about different stages for pumps. I know my county's department has 1500Gpm two stage pumps, yet others have single stage pumps. I did some searches here but didnt quite find what I was looking for. from what I have read, I think I have gathered that with two stages you a high pressure low Gpm and a low pressure high Gpm. I dont really understand how it works though, anyone have some diagrams or anything? Also, are there more than just two stage pumps? like 3 or 4 stages?


  2. #2
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    Default staged pumps

    I'm sure that if you go to Waterous or Hale fire pump web sites you can find what you are looking for and I know that both companies have wall charts and such to help you. I was looking for their sites on my rollodex cards but could not find what to input for Hale and Waterous is www. waterousco.com
    Good luck.

  3. #3
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    Default

    Well, i couldnt find anything on the Waterous web site, I did find an article on the Hale site here http://www.haleproducts.com/literatu...es/Singstg.pdf

    After reading it, it leaves me with some more questions.
    it said that a single stage takes water in on two sides of the impeller, what is that saying? does it mean there are two suction intakes like on either side of the vehicle for water to be taken in on? can an engine have two supply lines running to the pump on either side at the same time?
    also, it said the two stage has two impellers, one for high pressure and the other for low, does that mean only one is in use at a time? could the operator do something like high pressure on a few discharges and low pressure on some other discharges at the same time?

  4. #4
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    Default Fire Pumps

    Let me muddy the waters some more for you. I am an engineer (whoopee! ) and teach pumps some (even bigger whoope! ) but I don't know if I can explain this without using my hands .
    Anyway, many years ago...(in a galaxy far far away...oh wait...wrong story line)...when the fire service got away from positive displacement piston pumps and started relying on centrifical fire pumps, the motors of the day were gasoline powered, which had a limited horsepower, torque, and rpm output at an acceptable engine speed that would not blow the motor (bad thing). It takes a lot of torque and horsepower to move large volumes of water around because of the weight it must "push" (8.3 lbs per gallon at 300 GPM is over a ton of weight being moved every minute.
    Since the centrifical pump is able to (actually designed to) build on incoming pressure (good thing), the multi-stage pump became the standard because a "two stage pump" is basicly two pumps side by side in a common housing (there were also three and four stage pumps in service when high pressure fog attack hit the scene in a big way). The plumbing was/is designed in a way that you could/can either operate the pump with water coming into the two impellers of the pump at the same time and being pushed out by both at the same time (called the "parallel", "volume", or "capacity" setting...depending on the manufacturer) or water could/can be directed to only one side of the twin impellers and then routed over to the other impeller to further boost the pressure given to the water by the first impeller (called the "pressure", or "series" setting...once again depending on the manufacturer). The idea was that when you went from the "pressure" to the "volume" setting (this was/is done by a stem controlled clapper valve called the "change over valve") you could pump double the amount of water BUT at 1/2 the pressure at the SAME engine rpm.
    When I first learned to pump (on a 1959 American LaFrance Suburban Pumper with an ALF "Twinflow L" 750 gpm two stage pump - dang I am old ) the "rule of thumb" was that if you were in a situtation where you were going to have to pump more than 70% of the rated volume of the pump, you were to place the pump in "volume". Since most "bread and butter" fire attacks were two lines (1 1/2" at the time) flowing 100 gpm (actually 95 gpm) each, you rarely even came close to the 70% rule, and operated in "pressure" mode the majority of the time. If you were setting up to relay pump, fill tankers/tenders, or the world was burning down, then you would go to "volume" setting.
    THEN a lot of much improved diesel engines came along which had lots of horsepower and torque at much lower rpms of the motor (very good thing). This meant that a single stage pump with the right size impeller could do the same work as a gasoline powered two stage pump. It was a revolution in the fire service...no more having to figure out when you had to use that troublesome "change over valve" (which now is most commonly taught to be 50% of the rated capacity of the pump). For departments that did not have much time to train a pump operator, this made a fire pump much eaiser to operate, plus was easier to maintain also. A lot of departments still purchase two stage pumps with diesel engines for a lot of reasons...everything from "we have always had two stage pumps", "we have a lot of standpipes", "we need big water a lot" which is fine, you have to look at what works best for your situtation and area. Both the two-stage and the single-stage gets the job done (git'er done) and done well, BUT both types are only as good as the OPERATOR/ENGINEER.
    Did ANY of that make sense??
    Pray for the dead, fight like hell for the living! - Mother Jones

  5. #5
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    Default

    Yea, alot of that did make sense, thank you. Im not a firefighter though so some was a little over me. So it would sound like my department would probably be using theirs in the "pressure" mostly for hose fires in such where they are using two preconnects or a skid load. and then for the big ones where they got all the lines out and a couple monitors going they would put it in the "volume" setting. the pumps with more than two stages sounds like they would be really big in size because of more impellers?

    Thanks for the explination, this really interesting.

  6. #6
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    Default

    You are correct in saying that they would "usually" be operating in pressure mode!!! I think he did a VERY good job of explaining the difference!!!!

  7. #7
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    Default

    The Rosenbauer NH pumps do have multiple stages, and pump both normal pressures and high pressure simultaneously.

    Now bear in mind, this setup isn't intended for the same type of uses that you use a conventional two or three stage pump for, like pumping into high rise standpipes or sprinkler connections.

    I posted this so you could look at the cutaway at the link below and get some idea of how the multiple stages work.

    NH 1250 pump

    I'll keep looking for a cutaway view of a typical two stage pump.

  8. #8
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    Default

    The multi-stage high pressure impellers are are usually smaller as the implellers are creating more pressure with less volume, so they don't have to be as big. That's why a high pressure pump can fit in the same pumphouse with a volume pump.

  9. #9
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    Default

    Wow, thanks for all the info guys, thats some amazing stuff! that pump is crazy looking, its amazing that something like that can do so much. Thanks everyone.

  10. #10
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    Default

    rmiller,
    If you go to www.waterousco.com, click on Service and Training, Scroll down and click on "View the Service Manual" then click on "Miscellanious Information" you will find a very long list of helpfull information such as Centrifugal pump principle's of operation to Series/Parallel operation. Hope this helps you out.

    Chopper

  11. #11
    Forum Member Rescue101's Avatar
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    Default

    We've run Hale two stage pumps for years,still do.In "pressure"mode you can maintain up tp 50%of the pumps capacity at reduced engine speed compared to a single stage.In "volume"output and engine speed are similar to a single stage pump.As the others have stated,you can handle a majority of your calls in "pressure" which amounts to reduced engine wear(less rpms)and reduced fuel consumption.For a lot of you,these savings will be not worth the hassle of you having to educate your personnel in the PROPER use of the two stage.We keep most of our stuff for 25 years,in one capacity or another,and since we've had this pump style for years it just made sense to us to keep buying them.The pump mfgs have been working too,you can now drive a lot more pump with a lot less engine.So it really comes down to personal preference and what you need to do.If you need higher pressures to feed say a standpipe then perhaps you should consider a multiple stage pump.Otherwise a single should do just fine. T.C.

  12. #12
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    Default High Pressure & Firefighting

    Hello - I am curious if anyone has any information on the pros and cons of using a high-pressure line during fire attack. We currently have 2 trucks w/ third stage pumps; I personally want to get away from the thought of using a high-pressure attack line. Does anyone have any good reference material or articles/studies?

    Jason

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