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Is this bad for the pump?

  1. Jan 9, 2009 #1
    I was told that a pump in a heating system that from time to time pushes against closed valves is not good for the pump. If so, how will it affect the pump in the long run?
  2. jcsd
  3. Jan 9, 2009 #2
    It really depends on whether you also have a pressure unloading valve in the system. If so, there is no problem. Else, the pump sees excessive pressures; the usual result is blown seals.
  4. Jan 9, 2009 #3


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    If there is a proper relief on the outlet of the pump then it is not a bad thing at all. If you are counting on a pump's internal safety relief then it is not a good thing. I use the set up of a relief on the outlet port with the relief going back to the inlet of the pump all the time. The only thing you need to watch out for is the heating that will take place in that recirc loop.

    I guess it all depends on what pump you are referring to.
  5. Jan 9, 2009 #4
    Depends on the pump. I once worked at a plant where a very important (but small, like a pool pump size) was found to have its outlet valve inadvertently closed. Since this particular pump only runs occasionallly, it was OK but the question was, would it have wrecked itself if it had had to run? A mockup was built with a spare pump to duplicate the configuration. It was instrumented with temperature probes etc, and then started with the discharge closed. The test commenced with numerous observers including some from an interested regulatory agency. The pump temperature rose over the first ten minutes and then leveled off, vibration was normal, etc. As the first hour went by, the crowd of onlookers dissipated exponentially. I think they ran it for 12 hours, no change.

    So, depends on the pump. I wouldn't try it with a big expensive one. And the system design shouldn't rely on the pump "taking it."
  6. Jan 11, 2009 #5


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    It really depends on the type of pump. Some pumps are simply made to run with the exhaust 'dead headed'. I recall posting on something similar in a hydraulics related thread. Some hydraulic pumps have fluid pressure feedback to the back side of the piston. The piston rides on a cam. When the pressure exceeds a certain value the piston 'floats'. I believe this is what is called 'going out of stroke'.
    It is not really possible to answer your question without knowing more about the pump in question
  7. Jan 18, 2009 #6
    a lot of pumps require minimum flow thru them for various reasons, cooling being a big one, I think most likely seal failures are a major concern.
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