3.2.5 Richardson rule
Bob Richardson of Union Carbide suggested the heuristic that the
largest stream should be selected to control the liquid level in a vessel.
This makes good sense because it provides more muscle to achieve
the desired control objective. An analogy is that it is much easier to
maneuver a large barge with a tugboat than with a life raft. We often
use the expression that you can't make a garbage truck drive like a
Ferrari. But this is not necessarily true. If you put a 2000-hp engine
in the garbage truck (and redesigned the center of gravity), you could
make it handle just like a sports car. The point is that the bigger the
handle you have to affect a process, the better you can control it. This
is why there are often fundamental conflicts between steady-state design
and dynamic controllability.