Here is the story:
Since 10 years ago, I was questioned by end clients (internal/external) about how to detail the trigger conditions of interlock/permissives. For example, the heater is interlocked by a serial of conditions, like, tank level low, flow switch off, downstream valve open, or perhaps even the interlocks from other units. The condition could be combination of serial or parallel connections. Usually, I will just display one label on the HMI/SCADA screen to indicate interlock is Active when it’s triggered, but the operator wants to know more about which condition is triggering the interlock
With the old SCADA/HMI software, it’s difficult/troublesome to detail the conditions, so I always so “No, ready the manual”. But I am not sure, with Ignition, whether it can be done in a easier way?
Ways that I can think of are:
- Define the logic in PLC code and Ignition visualizes the logic on Ignition screen in a way of charts or predefined describable words.
- Define a pattern in PLC, but no specific logic for each interlock. Then predefine a table from Ignition, so the process engineer can enter the interlock condition from Ignition screen, and the condition will automatically generate the logic in PLC.
It’s not just limited to Interlocks, but also permissive, unit healthy signals or any signal which is concluded from other conditions.
I am currently working on a client Citect system, it’s using a predefined excel workbook for each devices (valve, pumps). In the workbook, it has a sheet for the interlocks, once the engineer enters the interlock condition detail in this excel sheet, it will then show up the interlock status and description on the Citect device faceplate, also the operator can click on the interlock to navigate to the place whether the interlock condition is triggered. It’s great idea, but not the simplest way, I reckon.
Has anyone realize the idea in you software? What’s the way you do?
Any comments is appreciated.