Not sure when cascade control makes sense? Unclear about its drawbacks, or how it's properly implemented? Then check out this recent screencast from the Learn ChemE series from the University of Colorado Boulder, Department of Chemical & Biological Engineering.
This particular video tutorial, produced by the faculty of Lafayette College, introduces cascade control, describes how it's implemented, and presents a block diagram for a reactor with a cooling jacket.
If you want more on process control, then check out the Learn ChemE Process Control playlist, or peruse the entire series for hundreds of tutorials on a wide variety of chemical engineering topics, from engineering computing and fluid mechanics to thermodynamics and numerical analysis.