Hot Cutover War Stories?
Modernizing automation systems while the plant continues to run requires a heck of a lot of planning. If you've been through one or several of these, what's the biggest lesson learned you'd offer others?
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Planning and Patience
I have been involved in a couple of hot switch over projects. They have been very successful. It takes a tremendous amount of planning and patience. One project took approximately 18 months where we switched the plant over 1 loop at a time. Planning was the key - the next week's loops were selected near the end of the week so that they could be pre-configured. The next day's work was decided the night before based on resources and other plant activities. The control loops were switched in the morning, typically one and it was turned over and tuned while indicators were switched in the afternoon. More complex loops typically took the whole day and the evening if required.
Patience was also a key! We didn't get greedy, we did what was on the list and didn't take on too much at one time. We didn't start the project if we didn't have a plan or the material in place and as much pre-work (configuration, calibration, etc.) completed as possible.
The other one I was involved with saw a control system switchover completed in 5 days but that had a year of planning behind it.
Use simple Cutover panels
I had have many Hot Cutover situations. At the beginning I designed with individual independent zones and interlocks: It was a useless effort cor centralized Control Systems.
Do clearly indicate the status of the cutover (old/new), make inputs to the Control System always available (test basic reporting, helps fine tuning).
I had a customer that even the system was already accepted, kept the cutover panel in place for months. When they decommission the old CS they have already forgotten the procedure and had some problems. Since then I attach the procedure to the panel.