To fully use the pump capacity, to lower the number of times of operation and stop, and select a pump to be operated in response to the plant condition.
A number-of-pump control unit of a control device for controlling the flow of plural pumps having a different capacity is provided with a number of pump changeover determining unit 20 for computing the controllable flow range on the basis of the Q-H characteristic 18 per each pump and all pump heads 19 in real time and for computing a number of operated pump pattern table for starting and stopping the pump when a pump, which can not be operated, is detected, and a circuit 21 for selecting a pump to be operated or stopped. The controllable flow range with the real number of operated pump pattern is obtained on the basis of the real number of operated pump pattern and the computed controllable flow range per each pump, and furthermore, controllable flow range with the real upper (restarting) or the lower (stopping) number of operated pump pattern is obtained on the basis of the computed number of operated pump pattern table and the controllable flow range per each pump, and restarting and stop of the pump is determined on the basis of results of these computing, and a pump to be operated or stopped is selected.
WATANABE YASUO
NONAKA MOTOMICHI
SAKAMOTO AKIRA
HITACHI ENG CO LTD