Citation

Dalzell G. Process. Saf. Environ. Prot. 2003; 81(6): 414-417.

Copyright

(Copyright © 2003, Institution of Chemical Engineers and European Federation of Chemical Engineering, Publisher Hemisphere Publishing)

DOI

10.1205/095758203770866584

PMID

unavailable

Abstract

The classical aspects of inherent safety are well known; elimination, substitution, attenuation etc. These make fundamental changes to the processing method or layout. There is another contributor which has not had the publicity and discussion that it deserves; the reduction in likelihood and personnel exposure through the longevity and reliability of the plant. Up until now it has also been difficult to measure. This paper offers a radical approach to considering its value. It argues that risk is proportional to the square of the operating cost. (Strictly speaking, this only applies to a facility which does not expose personnel beyond it boundaries, such as an offshore installation, and does not imply that cutting maintenance costs will reduce risks.) The argument it makes is a simple one. Risk equals likelihood times consequence. Likelihood is a function of cause which is usually human error or omission. This is a function of the activity level needed to run the plant and therefore the operating cost. Consequence is death and injury, a function of the number of people on the plant, the activity level and therefore the operating cost. Therefore, risk = opex squared. This could be used to justify more reliable equipment or better paint systems which minimize hazardous maintenance which is undoubtedly inherently safer. But, then again, who ever heard of an ALARP demonstration on a better paint system…?.