| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a control device and method for a direct feed water supplying system of large rate of flow structured so that a parallel operation is conducted with variable speed pumps, capable of controlling the rate of flow of each pump so that the rate is no higher than the cavitation limit. Ž<P>SOLUTION: A means is provided to compute the in-service pump suction head NPSH<SB>av</SB>from an approximating expression to give a synthesized loss head with respect to the rate of flow of a plurality of counterflow preventing check valves in parallel connection and the sensing value of a pressure sensor for sensing the service water main pipe pressure placed upstream of the check valves. The approximating expression of the requisite pump suction head NPSH<SB>re</SB>given by the pump maker is determined, followed by computing the condition that the in-service NPSH<SB>av</SB>-requisite NPSH<SB>re</SB>>margin head, from the obtained NPSH<SB>av</SB>and NPSH<SB>re</SB>, and if this condition is not met, the frequency of an inverter is held at the value at this time, and the pump speed is controlled at or below the cavitation limit rate of flow by inhibiting the pump(s) from being accelerated. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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