Patent ID: 9558854
Date: 2017-01-31
CPC Classifications: F04B,F04D,F22D,G21C,Y02E

Claim:
1. A method for providing override control for a feedwater pump recirculation valve, the method comprising: receiving a measured recirculation pump flow rate from a differential-pressure flowmeter, wherein the measured recirculation pump flow rate is a recirculation flow rate through the feedwater pump recirculation valve measured by the differential-pressure flowmeter; providing, by a controller, a control signal to the feedwater pump recirculation valve, wherein the feedwater pump recirculation valve regulates recirculation flow through a feedwater pump based on the measured recirculation pump flow rate to maintain a predetermined minimum recirculation flow rate through the feedwater pump; receiving one or more measurements of a current and a voltage of a pump motor that drives feedwater pump flow, the current and voltage being indicative of a consumed electrical power, wherein the current is measured by at least one current transformer, the voltage is measured by at least one potential transformer and wherein the at least one current transformer and the at least one potential transformer are connected to a motor control system; based at least in part on the one or more measurements, identifying an expected recirculation pump flow rate that corresponds to the one or more measurements using a predefined interpolation function; comparing the expected recirculation pump flow rate with the predetermined minimum recirculation flow rate; if the expected recirculation pump flow rate is below the predetermined minimum recirculation flow rate, comparing the expected recirculation pump flow rate with the measured recirculation pump flow rate; and if the measured recirculation pump flow rate is higher than the expected recirculation pump flow rate providing, by the controller, an override control signal to adjust a position of the feedwater pump recirculation valve and increase flow to above the predetermined minimum recirculation flow rate, wherein the override control signal overrides the control signal provided by the differential-pressure flowmeter.