I am working on the automation of an anaerobic digestion facility for treating agricultural waste. We are considering using Ignition’s SFC module to implement the vast majority of the logic controlling the behavior of the system – filling and emptying the digester, dealing with the products of the digestion, etc. – by directly controlling individual actuators in the installation from the HMI. We’d pass through a “dumb” PLC that would mostly just act as a liaison to control the actuators in the system and read sensor values (sending all this information back to the HMI). It might also include a safety routine to shut off the installation if the connection with the HMI is lost for a given period.
Answers to any of the following questions would be greatly appreciated:
If the HMI fails (OS craches, Ignition crashes, …) we would obviously like to regain control of the system quickly and keep running the SFCs. To have a second redundant installation, if I understand correctly, we would need to pay 50% the cost of the first including all the modules. To save money, could we, for example, not install the Tag Historian module in the backup installation and, until the master regains control, just not log anything to the database? Or not install Alarm Notification? Or does the backup need to have exactly the same configuration as the original?
Assuming we do not add automatic redundancy, can we save a backup of the gateway configuration, and when the main gateway goes down, manually launch another copy of Ignition on another computer? If the first copy is not running, would it be possible to quickly launch another using the same license? Or is the license tied to the computer and difficult to move?
Any ideas about how to automatically send an alarm when the gateway fails? (potentially from a process on another computer that polls Ignition regularly to make sure it is running)
What can we expect from an SFC in terms of reaction time - for example, time that it takes to change state when a transition condition goes from false to true?
Is the SFC module intended to be able to fully automate a system like this (one with fairly lenient timing constraints and few safety concerns)? Is it sufficiently reliable, and has this been done on existing installations? Or does it seem inadvisable to remove the logic from the PLC and put it in the HMI?
Thanks a million.