Precise control of pump outlet pressure
Thread Content
There is a pump currently used to transport hydrocarbon liquids, and changes in the density of these liquids cause variations in the pressure at the pump’s outlet. To stabilize the pump outlet pressure, it is planned to use a frequency converter, pressure transmitter, pressure control valve, and PLC control system to form two separate circuits for frequency control and pressure control. A pressure transmitter is used to measure the pressure in the pump outlet pipeline, and the PLC PID controller calculates the control value based on the difference between the value measured by this transmitter and the set value, thereby controlling the pump’s frequency converter and adjusting the pump’s speed to change the outlet pressure. At the same time, to ensure precise control of the pump outlet pressure, this pressure transmitter also forms a backpressure control loop with a control valve located at the pump outlet. It is hoped that at the beginning of pump operation, frequency conversion control will be used for rapid rough adjustment; after a certain period of time, a slower pressure control loop (with slowly set PID parameters) will be activated, thereby achieving precise control of the pump outlet pressure. Dear experts, could you help analyze whether this outlet pressure control scheme for pumps is effective? Could you share your successful experiences as well?
The original poster didn’t specify what type of pump it is; I assume it’s a centrifugal pump. Even if the density changes, why can’t the outlet pressure be controlled using outlet PIC-PV? The outlet pressure of the pump is adjusted by PV. My question: Can variable-frequency power regulation overcome the \"pressure changes\" caused by density variations? What is the underlying relationship? If the user requires a large pressure change, that is, a significant variation in the pump’s outlet pressure, then using variable frequency is useful; this results in a smaller pressure drop across the PV, which is what is meant by energy savings. @jiaguoyun
I really have never seen two control systems being used simultaneously; not to mention the high costs, if there is coupling between the two circuits, then the control valves will not perform well either. Generally speaking, to stabilize the pressure after the pump, a pressure transducer combined with a control valve works quite well; if the site conditions permit, both can be installed further away from the pump outlet.
It’s a complicated way of putting it; I suggest stating the specific details