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  1. #1
    JNB
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    Default Centrifugal vs diaphram pumps

    What kind of pump am I supposed to use? I used a water pump to wash my tractor and restricted the flow to increase pressure - ruined my pump. Now if I did that to my garden sprinkler pump - it will not ruin the pump. What is the differnce in pumps?

  2. #2
    Veteran Member
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    Default Re: Centrifugal vs diaphram pumps

    Quote Originally Posted by JNB View Post
    What kind of pump am I supposed to use? I used a water pump to wash my tractor and restricted the flow to increase pressure - ruined my pump. Now if I did that to my garden sprinkler pump - it will not ruin the pump. What is the differnce in pumps?
    Centrifugal pumps are not positive displacement so restrictng the flow does not damage them. If done for a long period of timethey may overheat..

    Diaphram pumps are positivedisplacement and if you try to stop or restrict the flow pressure will build until something stalls or breaks.

    Roy

  3. #3
    GT2
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    Default Re: Centrifugal vs diaphram pumps

    If it was a rubber impeller pump it is possible to over heat the impeller ( the water flow cools the pump blades) and damage it. But it would probably have to be severely restricted.

  4. #4
    Bronze Member eatenabean's Avatar
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    Default Re: Centrifugal vs diaphram pumps

    All Centrifugal pumps have a min flow. The flow can be restricted, but not under its min flow for a long period of time. Look at the tech manual and it should tell you the min flow.
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  5. #5
    Member Water Boy's Avatar
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    Default Re: Centrifugal vs diaphram pumps

    Quote Originally Posted by oldnslo View Post
    Centrifugal pumps are not positive displacement so restrictng the flow does not damage them. If done for a long period of timethey may overheat..

    Diaphram pumps are positivedisplacement and if you try to stop or restrict the flow pressure will build until something stalls or breaks.

    Roy
    Some of the pumps I use at work will turn the water to steam and explode if you dead-head them. Never a good idea to A: Restrict the inlet(cavitation) or B: restrict the Outlet(dead-head).

    WB
    Kubota B 2320 With BH and FEL

  6. #6
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    2006 Kama554; 92 Belarus 250AS

    Default Re: Centrifugal vs diaphram pumps

    Quote Originally Posted by JNB View Post
    What kind of pump am I supposed to use? I used a water pump to wash my tractor and restricted the flow to increase pressure - ruined my pump. Now if I did that to my garden sprinkler pump - it will not ruin the pump. What is the differnce in pumps?
    Are you pumping from a reservoir (tank/pond) or boosting the pressure of tap water? What type of water pump got ruined?

    If you are boosting pressure get a pressure washer. If you don't have positive pressure to the pressure washer you can add a centrifugal pump to feed it. Pressure washer pumps are positive displacement but they have unloader valves to protect the pump when flow is shut off at the wand and the motor keeps running.
    2006 Kama 554, 92 Belarus 250AS, Bombardier Outlander Max 400.

  7. #7
    Gold Member Shmudda's Avatar
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    Default Re: Centrifugal vs diaphram pumps

    Quote Originally Posted by oldnslo View Post
    Centrifugal pumps are not positive displacement so restrictng the flow does not damage them. If done for a long period of timethey may overheat..

    Diaphram pumps are positivedisplacement and if you try to stop or restrict the flow pressure will build until something stalls or breaks.

    Roy
    Roy,

    Restricting the flow on a centrifugal pump will most certainly damage the pump, you cannot do it as the fluid inside will heat up (depending whats being pumped) create air bubbles and cause cavation which then will totally destroy the pump.

    Diaphram pumps are the MOST forgiving pumps out there, thats why they are commonly called TRASH pumps. You can restrict the flow until they stall without really hurting them at all, in fact thats the beauty of those things they are cheap, will pump anything that fits thru the pipe and when the 1 million cycles of the diaphram finally kill the pump it's rebuilt for a fraction of the cost of new. The diaphram pump output is regulated by the air pressure put into it, plain and simple. We have them at work with the air on and regulate the discharge valve for how much water or oil we want flowing. Like I said they are the most forgiving pump out there.....

    Craig
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  8. #8
    Platinum Member Raspy's Avatar
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    Default Re: Centrifugal vs diaphram pumps

    Not all centrifugal pumps will be damaged by deadheading. I have one on a heating system that spends a lot of time deadheaded. And I found one running at a house that had been running against a closed valve for over five years.

    If you must restrict one side or the other, restrict the output side to prevent cavitation and keep the prseeure up. The output of a centrifugal pump is always restricted to a certain extent. Building head pressure in a diaphragm tank or pumping through a long piping system, etc. The output volume always depends on the piping restriction, or the head pressure, with a centrifugal setup. That's what pump chart performance curves tell you. Look at a well pump, for example. In my case the water is at 190 feet down and equals an 83 PSI restriction just to get started. That centrifugal pump works fine and would also work with water at ground level.

    Higher horsepower pumps can make a lot of heat and even be dangerous. It just depends on the particular one. If it's getting enough flow to keep itself within temperature limits, it's fine.
    John

    I only exaggerate enough to compensate for being taken with a grain of salt.

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