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Low-flow pump-off control

  • US 4,781,536 A
  • Filed: 09/10/1986
  • Issued: 11/01/1988
  • Est. Priority Date: 09/10/1986
  • Status: Expired due to Fees
First Claim
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1. A low-flow pump-off control device for deactivating a motor for a pump during conditions when a rate of supply of a source of fluid to be pumped by said pump is insufficient, said device comprising:

  • a pipe section having an inlet and an outlet, said inlet being connectable to said source of fluid to be pumped through said pipe section;

    a plurality of plates disposed in said pipe section, each of said plates respectively defining at least one orifice through which said fluid is caused to pass;

    a differential pressure switch for sensing a differential pressure between a pressure upstream of a first one of said plates and a pressure downstream of a last one of said plates that is at or below a set point indicative of a predetermined low flow rate of said liquid;

    a first timer in communication with said switch for accumulating periods of time at which said switch senses said differential pressure;

    a motor activation and deactivation means in communication with said timer for deactivating said motor when said accumulated periods of time total a predetermined amount; and

    a second timer in communication with said first timer which is activated when said accumulated periods of time total said predetermined amount, wherein said motor activation and deactivation means is in communication with said second timer and activates said motor when said second timer times a second predetermined amount of time.

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