How can the AO channel be replaced online without affecting the AO output?
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There is a problem now: we want to replace the existing DCS system with a PLC, but since the factory is still in operation, how can we switch the DCS AO channels to the PLC’s AO channels without any disruptions? I hope friends with experience in this area can give some good advice. Thank you all!
At present, one of our plans is to first switch the valve to manual operation using a handwheel, then remove the DCS AO and connect the wires to the PLC AO.
During automatic operation, it’s not advisable to do this; many systems have interlocks in place. For safety reasons, it’s recommended that you stop the system first before proceeding with any operations
The approach of first operating locally and then making the switch requires further refinement, such as checking whether the AO outputs of the PLC function properly together with similar output devices, and whether the PLC program monitors the opening degree of the valves.
It’s recommended to stop using it and replace it; are you going to use it without doing any testing? ? The loss from an accident stop is even greater
If it has to be done this way, it should not be a matter of considering system issues, but rather issues related to the valve positioner. If the locator has a holding function, it might be worth considering; otherwise, it’s better to use a bypass line and operate it with a manual valve. It’s recommended to park the car; after all, safety comes first