What is the effect of the opening degree of the centrifugal pump’s outlet valve on the pump’s pressure, flow rate, and current?
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What is the effect of the opening degree of the centrifugal pump’s outlet valve on the pump’s pressure, flow rate, and current?
As the opening of the centrifugal pump’s outlet valve increases, the pump’s outlet pressure decreases, while the flow rate and current increase
When a centrifugal pump is started, there is no water in the pump’s outlet pipeline; as a result, there is no pipeline resistance or head loss. After the pump starts, its head is very low while the flow rate is high. At this point, the motor driving the pump generates a large amount of power, which can easily lead to overloading and damage to the pump’s motor and electrical wiring. Therefore, it is necessary to close the outlet valve at the time of startup in order for the pump to operate properly.
As the opening of the centrifugal pump’s outlet valve increases, the pressure at the pump’s outlet decreases, while the flow rate and current increase. Therefore. When starting the pump, first close the outlet valve slightly, and then gradually open it once stability is achieved.
The opening degree of the pump outlet valve is directly related to the pump outlet flow rate. The relationship between flow rate and head must be referred to the Q-H curve: as the flow rate increases, the head decreases. The relationship between flow rate and power is determined by the Q-N curve: a higher flow rate results in greater shaft power and an increased current.
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In the case of standard design installation, when the opening of the outlet valve is increased, the outlet pressure drops from a high value to the rated head; the flow rate increases, and the current also increases.