Safety Instrumented Systems

While I am at odds with Paul Gruhn, PE (and others) regarding the merits of ESS vs PES, I heartily agree with his comments in an article
presented in the Feb issue of Intech magazine.

The article "Control Technologies for Safety and Production", co-authored by Frank Watkins and Kelly Flowers, advocates merger of the two disciplines to save costs associated with hardware, wiring, and startup.

Paul's contribution was a quote taken from his (and co-author Harry Cheddie's) book "Safety Shutdown Systems...", which favors, nay, strongly emphasizes the COMPLETE separation of the two.

I have more than 30 years experience in this field, and I too advocate separation. I have investigated several merged and one "almost complete" separation systems that failed catastrophically. In the "almost" one, TMR redundant transmitters were used for both functions in the interest of "productivity" and "cost" benefits. Instead. The actual outcome was $5,000,000 loss of reactor catalyst.

Unless you have first hand knowledge of the consequence of risk, do not profess knowledge of a solution that is intended to ameliorate the risk of failure.

I strongly urge you experts in this discipline to stick with the thesis... separation of religion and state... the former being cost, the
latter being safety. Hindsight is an excellent teacher. And you know what part of an animal is the "hind." Also, remember the moral to one of
Aesop's fables... "never put the fox in with the chickens!"

Phil Corso, PE
(Boca Raton, FL)

yogesh tapaswi

hello phil,
i am sorry i am communicating to u on this post as i donot know ur mail ID. will u plz send test mail to me on
[email protected]
there is little to discuss with u rgding "breaking of ind motor using 'pulse' DC injection"
I suspect that if Phil and I ever met, we'd be in almost total agreement. I have known of Phil for over 15 years, although we've never met. I teach about hardwired (relay) and solid state systems in my classes, as well as programmable systems. I was involved deeply with solid state systems earlier. I'm all for them (in the right applications).