8
For further information www.imi-precision.com
International functional
safety standard
1. Risk & Risk analysis
Safety can be defined as "freedom from
unacceptable risk". This definition is important
because it highlights the fact that all industrial
processes involve risk. Absolute safety, where
risk is completely eliminated, can never be
achieved; risk can only be reduced to an
acceptable level. Therefore all risks should be
reduced to as low as reasonably practicable.
IEC 61508 provides an alternative to Risk
Matrix, called Risk Graph. This method focuses
on the evaluation of risk from the point of view
of a person being exposed to the incident
impact zone. It is consequence driven and four
parameters are used to characterize a potential
hazardous event: Consequence (C), Frequency
of exposure (F), Possibility of escape (P) and
Likelihood of event (W). The following chart
shows an example of Risk Graph.
97105
Inline
97105
NAMUR
98025
NAMUR
& Inline
