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Layers of Protection Analysis
Process hazard analysis (PHA) teams
use engineering judgment to decide if additional safeguards are needed
to protect against accident scenarios they identify. This subjective
approach can lead to disagreements and possibly inappropriate measures
to reduce risk. A more rational and objective approach is needed, at
least when considering risk remediation measures for high risk scenarios
or those that are expensive to implement. Layers of Protection Analysis
(LOPA) was developed for this purpose.
LOPA is a simplified risk assessment
method. It provides an objective, rational and reproducible method of
evaluating scenario risk and comparing it with risk tolerance criteria
to decide if existing safeguards are adequate, and if additional
safeguards are needed. LOPA can be viewed as an extension of PHA.
Services Offered
Primatech facilitates LOPA studies
for clients. We also help decide which safeguards can be considered by
LOPA and we help determine their failure probabilities.
Primatech applies LOPA after a PHA
has been performed. Typically, high risk scenarios are first identified
for consideration. Individual hazard scenarios, defined by
cause-consequence pairs, are analyzed. LOPA considers safeguards that
are Independent Protection Layers (IPLs), defined as those whose failure
is independent of any other failures involved in the scenario.
A key part of LOPA is the
determination of the Safety Integrity Level (SIL) provided by the IPLs
involved in the scenario. The SIL is usually defined as a Probability of
Failure on Demand (PFD). These SILs are used in LOPA to assess scenario
risk and compare it with risk tolerance criteria to decide if existing
safeguards are adequate, and if additional safeguards are needed.
Primatech has performed a variety of LOPA studies. We
have produced templates for use with Primatech's software package,
PHAWorks™, to conduct these studies. We have also developed extensions
of LOPA to address human factors and process security.
Primatech offers the training courses
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