Page 97 - Serious Incident Prevention How to Achieve and Sustain Accident-Free Operations in Your Plant or Company

CH07pp068-82 4/10/02 12:50 PM Page 75

Understanding the Risks 75

(Highest) (Lowest)

10 0 10 -1 10 -2 10 -3 10 -4 10 -5 10 -6

1 in 1 1 in 1,000,000
• • Selection of switch
dissimilar in shape
Missetting large or location to desired
valves (no status switch
indicator except
open or closed) • Two-person team
• • (one does, one

Crew reaction • Missetting large checks, then roles
are reversed)
during disaster manual valves
Technician seeing (controlled by
an out of calibration procedure, keys,
instrument as in chaining, etc.)
tolerance
• •

Simulated military General error of omission
emergency for items embedded in
procedure
• • Selection of key-operated switch
rather than non-key switch (does
Passive inspections
•
(general walk-around) not
General error of
omission (no control
room display)
•
Monitor/Inspector fails • General errors of commission, eg.,
to recognize initial error misread label and selected wrong
by operator switch
•

Simple arithmetic errors (without
re-doing calculation on separate
paper)

FIGURE 7-2. Estimates of human performance error rates. (From System Safety
2000 by J. Stephenson. Copyright 1991 by Van Nostrand Reinhold. Reprinted by
permission of John Wiley & Sons Inc.) 3