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  1. #1
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    Default 1 vs 2 stage pumps

    We've always used 2 stage pumps in the past. I know the benefits of 1 stage (price, weight, maintenance, training, etc.) each but would like to know from anyone who has changed from 2 to 1. Any complaints? Would you go back to 2 or stay with 1 stage. Is there much of a difference in engine RPM when pumping a lower flow / high pressure type hoseline (300# booster?)


  2. #2
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    Default Switching from Dual to Single Stage Pumps

    We made the switch from dual to single last year on our new pierce. The single is much easier to teach to new operators. We have not had any issues. We do still run a Mack CF with a Hale dual stage 1500. The pierce has a 2000 gpm single stage hale. With the torque of the new diesel engines, I don't think the dual stage is required anymore like the old gasoline engines of the 60s.

    Mark

  3. #3
    Forum Member Rescue101's Avatar
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    Up to half the capacity of a two stage pump you will see roughly a 25-30% rpm reduction for a given flow.Over 50% of capacity it makes little difference as the pump will be in volume same as a single stage is all the time.Over a 20 year stretch you'll probably save some wear and money with a two stage.But with the simplicity and efficiency of the new singles is it worth it? I think we've seen our last two(stage). T.C.

  4. #4
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    Default Two stage vs. single stage pump

    Unless you have stand pipes in 15 - 30 story buildings to pump you don't need a two stage pump IMHO.

  5. #5
    Forum Member Res343cue's Avatar
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    Quote Originally Posted by donethat View Post
    Unless you have stand pipes in 15 - 30 story buildings to pump you don't need a two stage pump IMHO.
    Or in places where you relay pump, or where water supply may become an issue, or where you have lots of hills.... There's alot more to it than just tall buildings.
    Quote Originally Posted by ThNozzleMan
    Why? Because we are firemen. We are decent human beings. We would be compelled by the overwhelming impulse to save an innocent child from a tragic, painful death because in the end, we are MEN.

    I A C O J
    FTM-PTB


    Honorary Disclaimer: While I am a manufacturer representative, I am not here to sell my product. Any advice or knowledge shared is for informational purposes only. I do not use Firehouse.Com for promotional purposes.

  6. #6
    MembersZone Subscriber Golzy12's Avatar
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    2 stage pumps are much more efficient than single stage pumps when they are used correctly. Most firefighting is done using a couple hand lines run at a high PSI and a low flow. Large single stage pumps aren't able to do high pressure low flow as effectively as a 2 stage pump. When you increase the RPM's on a single stage pump you increase the pressure and also the flow, but if your only using one hand line the increase in flow can't all discharge out of that one hand line, all that flow into one hand line is like trying to cram a watermelon down an exhaust pipe. When the water can't all get though the discharge it can cause recirculation cavitation in the pump. Recirculation cavitation is different from intake cavitation. With intake cavitation you don't have enough water, with recirculation cavitation your trying to discharge more water then you can fit through the discharge. This causes the excess water to change direction inside the pump and go places that it shouldn't (like down the shroud of the impeller), that then causes pitting inside of the pump and causes some other major damage. Using a 2 stage pump correctly (using it in pressure when pumping less the 75% of capacity, then switching over to volume when pumping greater that that) will decrease the chances of recirculation cavitation in a pump. The series position is intended to be used for high pressure with low flow. When used in series the engine doesn't have to create the high RPM's that you would need to get that same pressure out of a single stage pump. The only time a single stage pump is more efficient is when it's being used at or near capacity. How many times a year do you operate your pump at capacity?

  7. #7
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    Quote Originally Posted by FD1976 View Post
    We've always used 2 stage pumps in the past. I know the benefits of 1 stage (price, weight, maintenance, training, etc.) each but would like to know from anyone who has changed from 2 to 1. Any complaints? Would you go back to 2 or stay with 1 stage. Is there much of a difference in engine RPM when pumping a lower flow / high pressure type hoseline (300# booster?)
    On our older units we have two stage pumps and were constantly having problems with the switch over valves. Every since the early 90's we have been all single stage the only way I would go back is if we were to order a dedicated brush/forest fire unit which we currently dont have but arent in any real need for one right now. But maintence and reliability are the biggest benefit we hae noticed.

  8. #8
    MembersZone Subscriber Paddiegrunt's Avatar
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    L.A. County Fire switched to single staged pumps in 1985, In my 24 as an Engineer, I never had a problem and I used them on everything from a dumpster to a 5,000 foot lay on a brush fire
    Slop sink, Flags and pump 150
    Getting there is half the fun

  9. #9
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    I fought this same battle in 2004 when I speced a pumper. I wanted to stay with a 2-stage.

    Contacted Waterous and Hale to reinforce my argument. Bad idea. Both manufacturers said the trend is towards single stage pumps for the reasons already mentioned in this thread.

    I understand that a 2-stage saves the engine. But I have to tell you, I have never seen a premium diesel engine ever wear out in a fire truck; the rest of the truck will fall apart first.

    I have, however, had a couple dozen pump overhauls performed. Maintenance is simpler on a single stage. No changeover valve, no pressure/volume indicator switches, less moving parts.

    Oh well. Just another one of those things I can tell the young whipper-snappers about after I retire, like riding in open cab trucks and on the rear step. Ooops. I am beginning to tell my age.

  10. #10
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    Thanks for all the replys. Like I stated, there are many benefits with few disadvantages. Probably like most depratments, when we arrive at an alarm we are pumping 1 or 2 1-3/4" handlines or maybe a 3/4" booster for brush, trash, etc. Very rarely will the pump be used to rated capacity. So theres not much of a noticeable increase in engine RPM / noise when pumping low volume / high pressure? If not, I think it's a no-brainer. Thanks again.

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