Page 98 - Serious Incident Prevention How to Achieve and Sustain Accident-Free Operations in Your Plant or Company

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76 Serious Incident Prevention

ations with potential for serious incidents, assumptions made without
checking it out can lead to catastrophic consequences.

Understanding the Role of Human Error

Managers must have a firm understanding of the role human errors can
play in serious incidents. As illustrated by Figure 7-2, estimates of human
performance error rates for various tasks range from a high probability
(e.g., 1 in 10) to a very low probability (e.g., 1 in 100,000). When human
errors can lead to severe consequences, managers must understand the wide
range of potential responses and ensure tasks are designed to facilitate cor-
rect responses.
Some environments have the unfortunate characteristics of being both
error inducing and unforgiving in the event an error is made. In the pres-
ence of these conditions, preventative actions must be sustained to effec-
tively block the pathway leading to incidents with severe consequences. In
petrochemical, utility, and other similar operations, conditions such as un-
planned shutdowns resulting from operational upsets can create stressful,
error-inducing environments. The human error accident causation model, as
illustrated by Figure 7-3, confirms that preplanned, proactive actions are
vital in helping ensure plants are shut down safely. Examples of proactive
actions helpful in maintaining safe conditions during shutdowns include:
(1) development of procedures, checklists, and other specific job aides; (2)
operator training; and (3) testing and calibration of critical instrumentation.
Regardless of the type of operation, the focus should be on identifying and
implementing specific actions necessary for reducing the potential for inci-
dents due to human error.
Although accidents typically have multiple causes, investigations often
indicate some form of human failure in the sequence of events leading to
the incident. Some human errors have immediate impact on safe work and
result in adverse effects leading directly to an incident. These types of er-
rors are often committed by front-line personnel at the point-of-control and
are commonly referred to as unsafe acts or “at risk” behaviors.
Other types of critical human failures lead to conditions categorized as
latent conditions. These types of conditions may be present for many years
before they combine with at-risk behaviors and other random circumstances
to lead to an incident with catastrophic consequences. Such latent condi-
tions include poor design, gaps in supervision, training deficiencies, inac-
curate procedures, faulty planning, and less-than-adequate equipment.
While unsafe acts having direct adverse impact are usually committed by
hands-on personnel, latent conditions are often attributable to failures in the