Imagine you’ve set up a CHEMCAD simulation that includes initial guesses like recycle streams or SCDS columns. You then click Run All, only to realize that you forgot to save your work before running the simulation. Yikes! If the simulation doesn’t converge, you’ll find yourself staring at a simulation flowsheet with yellow and red warning flags. You’re not sure what went wrong, but you know that this flowsheet has no solution, and now you’ll need to troubleshoot.
Resetting unit operations and recycle streams to their values from before the run could be a tedious task, but you need to return to those settings to pinpoint the problem. And while CHEMCAD does have an Undo command, it’s meant to revert a single change, not a simulation run.
That’s where CHEMCAD’s Load Last Snapshot feature comes in.
To take advantage of this feature, be sure the Take a snapshot before running flowsheet box is checked in the Convergence Parameters dialog (Home tab > Setup group > Convergence) before you start working on a simulation. This box is checked by default, and it’s recommended that you leave this feature on.
When you run a simulation and encounter issues, simply go to the Specification tab in the ribbon menu and click Load Last Snapshot. This action restores your simulation inputs to pre-run conditions. You can think of Load Last Snapshot as an Undo button for the Run command.
After loading the snapshot, you can then focus on editing the simulation settings to resolve the underlying issues that caused the convergence failure. You can run and then roll back calculations as many times as needed to find a solution.
Load Last Snapshot won’t solve your convergence issues, but it does provide a quick way to reset your input conditions.