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"Soft-Start" a pump with "pressure"?

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  • RickDelta
    RickDelta Member Posts: 403
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    "……if you introduce air in the chamber the tips of the volute will heat up and the pump will cavitate". - Leonz

    so ….. your revoking your statement of fact (above) as posted??

    ….. you do understand that overwhelming the pumping chamber with air bubbles …… the impellers have almost no effective contact with the water.

    It cant cavitate because the required density of the water is gone!

  • jumper
    jumper Member Posts: 2,282
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    Returning to original topic. OP needs to consult a qualified electrical engineer.

    First a centrifugal pump is a soft start device. This is not to say that even gentler devices are not used. For example PeerlessPump offered a set with fluid coupling.

    Second consideration is torque vs rpm curve for both motor and pump.

    Third utility may offer special price for stuff operating 24/7. It enhances grid stability. And proper phase correction can reduce RVA issue.

  • RickDelta
    RickDelta Member Posts: 403
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    "First a centrifugal pump is a soft start device" - jumper

    ….. can you elaborate on that please?

  • PC7060
    PC7060 Member Posts: 1,173
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    I second Chris’s vote for a “good grief” icon!

  • RickDelta
    RickDelta Member Posts: 403
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    ……. you two must function at the same level then! …… awesome!! : )

  • PC7060
    PC7060 Member Posts: 1,173
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    The term is “shudder” when dealing with controls systems.

    ethicalpaul
  • RickDelta
    RickDelta Member Posts: 403
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    …. I stand corrected Thank-you! (dammed spell checker has its own mind!) : )

    PC7060
  • RickDelta
    RickDelta Member Posts: 403
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    Now is my way clear, now is the meaning plain:
    Temptation shall not come in this kind again.
    The last temptation is the greatest treason:
    To do the right deed for the wrong reason.

  • Jamie Hall
    Jamie Hall Member Posts: 23,415
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    I don't know why I bother… but I can't resist. There is a term aircraft engineers and pilots use called "flutter" You may or may not feel it in the airframe of the controls, and it occurs when a control surface oscillates more or less violently. If the airframe is properly designed and you stay within the limit speeds of the airframe it won't happen unless something has broken or slacked off. Then there is aerodynamic buffeting, which is occasioned by a stalled or partially stalled surface causing one or more flying surfaces — most often the horizontal stabiliser — to encounter turbulent air from the stalled surface. Not all aircraft exhibit aerodynamic buffeting before the wing stalls, and in those aircraft an angle of attack sensor (or sensors) activates first the stick shaker and, if that doesn't wake the flying pilot up, it activates a stick pusher — which can be overcome by the pilot, but takes a good deal of pull to do on aircraft with control feel. On aircraft without feel — the entire Airbus fleet — the flight computer is supposed to prevent stalls. It usually works. There are other sources of aerodynamic buffeting caused by atmospheric conditions, notably wake turbulence and thunderstorms, but also sometimes severe windshear, but these have a distinctive feel to them.

    On the pilot not properly recognizing a stall… it does happen. The most common victims are people with more money than brains flying hot aircraft with inadequate training, although in one tragic case (Air France flight 447) it was less a money problem than an inadequate training problem., and there have been a few commercial cases where it was inadequate or slightly misleading training combined with inexperience.

    I might add that unless the stall leads to an unrecoverable spin or it occurs at too low an altitude it is pretty much a non-event, assuming it is recognised. Advanced fighter aircraft deliberately use deep stalls as a combat tactic — a trick developed by the Swedes. All pilots train through a variety of stalls, to recognise them and make recovery automatic.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    PC7060
  • leonz
    leonz Member Posts: 1,154
    edited April 28
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    No, I am not revoking the statement of fact. Any centrifugal pump or motor that does not have enough fluid in the pump chamber will cavitate if left energized long enough.

  • RickDelta
    RickDelta Member Posts: 403
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    I guess I don't understand what your saying here,

    lets say my pump's chamber takes 2 gallons of water to fill. Your saying if I take that level of water down to lets say one cup of water, this will cause the water to cavitate inside the chamber ??

    leonz
  • RickDelta
    RickDelta Member Posts: 403
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    ….. that's all very informative stuff Jamie Thank-you!

    ……but what's that got to do with the question I asked? : (

    "…. so, lets say your on break up in the crew's rest area of a 747 and your co-pilot pages you "Captain , the control stick is shuttering violently" you would have no clue of what he's talking about?? ….. you would just go back to sleep??" - RickDelta

    PC7060
  • Jamie Hall
    Jamie Hall Member Posts: 23,415
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    No… if the two guys I'd left in the front office seemed to be having trouble figuring out the stick shaker, I'd be down there right now — and set the power, angle of attack, and trim to my memorised values for cruise. Then… when we got back on the ground, there might be a bit of discussion about training or alternative occupations…😠

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    PC7060
  • RickDelta
    RickDelta Member Posts: 403
    edited April 28
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    …… well, I'm sure the co-pilot would not wake the sleeping captain if the plane wasn't in harm's way. His calling you would be likened to as on a ship "Captain to the Bridge"

    You made the point :

    " ….., and I have never yet heard the term "shutter" applied to an airplane's behaviour. Would you kindly enlighten me from your store of knowledge?" - Jamie Hall

    ….. yet you knew exactly what I was talking about! (as you have just stated above) I didn't have to "enlighten" you at all ….. you already knew.

  • Erin Holohan Haskell
    Erin Holohan Haskell Member, Moderator, Administrator Posts: 2,321
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    How did we get here??

    I think this discussion has run its course and is becoming antagonistic. I'm closing it so we can all stay friends. And with that, a friendly reminder that we're here to help and learn from one another, not stick it to people by proving them wrong. Thank you.

    President
    HeatingHelp.com

    LRCCBJPC7060RickDeltaCLamb
This discussion has been closed.