Reductio Ad Absurdum, which is Latin for "reduction to absurdity, is a rhetorical tactic which attempts either to disprove a statement by showing it inevitably leads to a ridiculous, absurd, or impractical conclusion, or to prove one by showing that if it were not true, the result would be absurd or impossible. As examples, it can be used in the classic parent child permission dispute:


The child is in trouble for skipping school, so tells his father, "All of my friends were going!" The father responds, "Well, if all of your friends were going to jump off of a bridge, would you do that, too?"


Or perhaps as a cruel put down:


Your friend says, "If I rub my lucky rabbit's foot, then I will do well on this test." You respond, "So, if it brings good luck, then I need to rub it so that my mum's cancer will go away, and my dad will get a new job, and our family will win the lottery.”


In this case, you might win the argument, but lose the friend.


In my professional sphere, there is much debate about Process Safety Return on Investment (ROI). Echoing the perennial problem with marketing spend, where “you know half of it is worth it; the question is which half?”, it is fiendishly difficult to determine what the optimum spending on Process Safety is. One tactic to at least see what one boundary looks like, the one where nothing is spent on Process Safety, we could apply the ‘Reductio Ad Absurdum’ principle and see what that looks like.


Let’s take a new, grassroots 500,000 bbl/d refinery in the Middle East. In order to minimise capex and opex, a cavalier operator instructs the contractor to focus on designing a plant which will start up and operate, while deliberately neglecting any equipment or instrumentation which would exclusively be designated for Process Safety. So out go any Safety Instrumented Systems (trips), Safety Valving (PSVs, BDVs), Consequence Mitigation (Active and Passive Fire Protection Systems, Bunding, Gas Detection, Emergency Egress etc) or Safety Training. When oil refineries were first designed and built over 100 years ago, I guess this was close to the remit and operator gave to a designer. And compared to a typical current design, there would probably be considerable cost saving.


So far so incident free. And then you start the refinery up. And pretty soon you’ll experience a credible process deviation, which, due to the complete absence of reactive and mitigative Process Safety barriers, will probably create a series of damaging, possibly fatal consequences, the costs associated with which will most likely far outweigh the initial benefits gained. This equates to a negative PS ROI.


We can also look at the other boundary, where a different and extremely timid operator’s obsession with Process Safety leads him to instruct the contractor to design and inherently safe facility. Cost no object - only (very) deep pockets. In which case, you’d probably be better to spend your money on something else, or even keep it in the bank at 0.01% annual return. Again negative PS ROI.


So our little philosophical exercise has demonstrated that you can easily spend too little or too much on Process Safety. Much harder is to spend the right amount. In the end, it boils down to what your appetite is for the size of the holes in your Swiss Cheese. Bon appetit!

swiss cheese