Operation of centrifugal pumps
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Why is it necessary to determine the exact opening degree of the outlet valve based on changes in current after starting the centrifugal pump?
Such a sophisticated issue… It seems to be intended to prevent sudden spikes in current
Theoretically, this should not happen; in practice, however, changes in processes and equipment can cause the motor to experience overcurrent. In such cases, the flow rate is controlled by adjusting the opening degree of the pump outlet valve, thereby preventing the motor from experiencing overcurrent.
It is also possible to open the valve by monitoring the outlet pressure instead of the current; the main purpose is to control the current
Can the specific opening degree of the valve be determined based on the current?
The opening degree of the valve cannot be determined based on the current, but the magnitude of the current can be controlled by turning the valve on and off.
The opening degree of the outlet valve is not controlled based on current. Instead, the opening degree of the outlet valve is determined based on the process requirements, and then the current is checked to see if it is within the normal range. You’re putting the cart before the horse.
Based on the flow rate and pressure requirements of the process, then consider the current situation.
These days, in many installations of ordinary small centrifugal pumps, there are no ammeters on site; they are only installed on the power distribution cabinets in the control room~~~~
Changes in motor current are not only related to flow rate; there are many other factors that influence it.
Why is it necessary to determine the exact opening degree of the outlet valve based on changes in current after starting the centrifugal pump? Regarding just the question posed by the original poster, for a pump with a fixed impeller, the current increases as the opening degree of the outlet valve increases, and this relationship is approximately linear within a certain range. In extreme cases, if fully opening the outlet could cause the motor to overload and burn out, it is necessary to monitor the motor current while opening the outlet valve. While meeting process requirements is important, for systems that have already been built, ensuring the integrity of the equipment is equally crucial.