Method and apparatus for preventing pump cavitation
First Claim
1. A method of controlling a system having a pump driven by an engine, said pump having a discharge conduit with a variable flow rate controller to prevent cavitation due to engine overspeed comprising the steps of:
- continuously sensing the speed of said engine and comparing the speed to a preselected set point speed;
generating a command signal when said sensed speed exceeds said set point speed;
actuating said flow controller with said command signal to change the flow rate of said discharge conduit by a predetermined decrement;
subsequently blocking said command signal from activating said flow controller for a selected time interval to permit the flow rate to reach steady state, while reducing energy input to the engine to cause said engine speed to drop below said set point speed, whereby said engine speed is maintained substantially at said set point speed to prevent cavitation in the pump.
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Abstract
The speed of an engine driven pump is sensed and compared with the desired maximum operating speed to detect overspeed. The discharge of the pump is controlled by a variable flow rate controller. When an overspeed condition exists, a command signal is sent to the discharge controller to reduce flow by a discrete decrement. The control signal is blocked after activating the controller for a preselected time interval. During the blocking interval the engine speed is maintained substantially at the operating speed by cyclical reduction of the power input thereto.
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Citations
10 Claims
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1. A method of controlling a system having a pump driven by an engine, said pump having a discharge conduit with a variable flow rate controller to prevent cavitation due to engine overspeed comprising the steps of:
- continuously sensing the speed of said engine and comparing the speed to a preselected set point speed;
generating a command signal when said sensed speed exceeds said set point speed;
actuating said flow controller with said command signal to change the flow rate of said discharge conduit by a predetermined decrement;
subsequently blocking said command signal from activating said flow controller for a selected time interval to permit the flow rate to reach steady state, while reducing energy input to the engine to cause said engine speed to drop below said set point speed, whereby said engine speed is maintained substantially at said set point speed to prevent cavitation in the pump. - View Dependent Claims (2, 3, 4, 5, 6, 7)
- continuously sensing the speed of said engine and comparing the speed to a preselected set point speed;
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8. Apparatus for controlling a system having a pump driven by an engine, said pump having a discharge conduit with a variable flow rate controller to prevent cavitation due to engine overspeed comprising:
- means for sensing the speed of said engine and generating a signal output proportional thereto;
comparator means electrically coupled to said sensing means to derive a signal input therefrom, said comparator means being operative to compare said signal input with a predetermined value corresponding to the maximum operating speed of the engine and generate a command signal when said engine speed exceeds said maximum operating speed;
control means operatively coupled to said variable flow rate controller, said control means being adaptable and arranged to receive said command signal and actuate said controller to change the flow rate in said discharge conduit by a predetermined decrement, said control means including means for interrupting the response thereof, to said command signal for a preselected interval following activation of said controller to permit the flow rate to reach steady state conditions; and
engine control means adapted to derive an input from said command signal and reduce the energy input to the engine to cause said engine speed to drop below said maximum operating speed, whereby said engine speed is maintained substantially at said operating speed to prevent cavitation. - View Dependent Claims (9, 10)
- means for sensing the speed of said engine and generating a signal output proportional thereto;
Specification