As a process consultant, one regular request that crops up is to debottleneck a process. That is, identifying what stage limits the capabilities of a plant. It could be vessel, pumps, compressors… actually it usually turns out to be the compressors, as they are expensive pieces of hardware, and sized to just barely meet the design intent (provocative statement, rotating machinery engineers!).
Now, what happens that as you remove one bottleneck, another one crops out, which you will tackle ad infinitum until your rate of return drops below your tolerance limit.
To put this in perspective, I’ve attached a video of a new road which was meant to debottleneck traffic by replacing a curvy toll bypass with a straight length. Problem is, it dead ends from a 4-lane road to a 2-lane road which feeds into another 2-lane road, which is the real bottleneck.
Photos of the link road follow, in a direction opposite to the video just to confuse things:
Posted by Wata 
Wata - Malaysian Oil and Gas Engineer 