Steps for switching off a variable-frequency pump
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Steps for switching off a variable-frequency pump: How to do it in such a way that flow rate remains stable or experiences only minimal fluctuations, without causing damage to the pump or other equipment
We have a variable-frequency centrifugal fan and a constant-frequency centrifugal fan that serve as backups for each other. Before starting, the variable-frequency fan operates at a constant frequency; after startup, variable frequency is applied to make gradual adjustments.
Set auto-start within the DCS system!
Reduce the frequency to the minimum speed; ensure both pumps operate at the same frequency, and then switch them off
4.8.1 Switching from valve control to frequency conversion control 4.8.1.1 Change the control of HC8103A from cascade control to manual control; while ensuring a stable flow rate at FIC8103, manually reduce the OP of HC8103B and increase the OP of HC8103A until the OP of HC8103A is set to 105% at full open. 4.8.1.2 Change the control mode of FIC8103 from automatic to manual, and adjust the OP value of FIC8103 to be equal to that of HC8103B. 4.8.1.3 Change the control mode of the frequency conversion controller HC8103B from manual to cascade control, and change the control mode of FIC8103 from manual to automatic. 4.8.2 Switching from frequency conversion control to valve control 4.8.2.1 Change the control mode of HC8103B from cascade control to manual control; while ensuring a stable flow rate at FIC8103, manually reduce the OP value of HC8103A and increase that of HC8103B, until the OP value of HC8103B is set to 105%, which represents its full open position. 4.8.2.2 Change the control mode of FIC8103 from automatic to manual, and adjust the OP value of FIC8103 to be equivalent to that of HC8103A. 4.8.2.3 Change the mode of the valve-controlled HC8103A from manual to cascade control, and change the control scheme of FIC8103 from manual to automatic.