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Method and apparatus for protection of pump systems

  • US 4,650,633 A
  • Filed: 07/02/1984
  • Issued: 03/17/1987
  • Est. Priority Date: 07/02/1984
  • Status: Expired due to Fees
First Claim
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1. In a nuclear power plant having a fluid-filled reactor vessel with a vapor outflow line for removing vapor from said reactor vessel, liquid inflow means for injecting liquid to said reactor vessel, said inflow means including an inflow line, a centrifugal pump disposed along said inflow line having an inlet and an outlet, an induction motor to drive said pump, flow control means along said inflow line between said pump and said reactor vessel from said pump, and means for generating a first control signal in response to liquid level in said reactor vessel and net vapor outflow versus liquid inflow with respect to said reactor vessel, said first control signal generating means being effective to generate a first signal to open and a second signal to close said flow control means to maintain liquid level in said vessel within predetermined limits, a pump and pump motor protection apparatus comprising:

  • means for measuring the pressure of said liquid in the inlet of said pump;

    means for measuring the temperature of said liquid in the inlet of said pump;

    means for determining a required subcooling for said pump at the instantaneous temperature of said liquid in the inlet of said pump;

    means for determining the enthalpy of said liquid in the inlet of said pump from the pressure and temperature of said liquid;

    means for comparing the enthalpy of said liquid in said inlet against the required subcooling and for generating a first indicative signal when the enthalpy of said liquid fails to exceed the required subcooling, whereby said first indicative signal indicates potential cavitation in said pump;

    means for developing a signal indicative of the instantaneous power consumed by said motor;

    means for comparing the level of power consumption by said motor against a predetermined maximum power and generating a second indicative signal should said power limited be exceeded whereby said second indicative signal indicates potential pump motor overload;

    an OR GATE for receiving said first and second indicative signals and generating a unipolarity second control signal in response to either said first or said second indicative signals; and

    control signal summing means for algebraically summing said second control signal with said first control signal to develop a valve position signal to close the positioning of said flow control means;

    whereby said flow control means is moved toward its closed position in response to an indication of motor overload or potential cavitation in said pump.

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