Safety Management System

LOPA
Layer of Protection Analysis (LOPA)

Layer of Protection Analysis (LOPA) is a methodology for hazard evaluation and risk assessment. On a sliding scale of sophistication and rigor, LOPA lies between the qualitative end of the scale (characterized by methods such as hazard and operability [HAZOP] and what-if) and the quantitative end (characterized by methods using fault trees and event trees). LOPA helps the analyst make consistent decisions on the adequacy of the existing or proposed layers of protection against an accident scenario (see diagram below). This decision-making process is ideally suited for coupling with a company's risk-decision criteria, such as those displayed in a risk matrix. LOPA is a recognized technique for selecting the appropriate safety integrity level (SIL) of your safety instrumented system (SIS) per the requirements of standards such as ANSI/ISA-84.00.01.

ABS Consulting's LOPA approach gives companies a viable tool to fit the niche between hazard evaluation/process hazard analysis (PHA) and quantitative risk assessment. Many of our customers have found LOPA to be a cost-effective addition to PHA revalidations. The LOPA results support (1) assigning priorities to recommendations and (2) developing safety requirement specifications for safety instrumented systems (a necessary step in complying with ANSI/ISA-84.00.01-2004, Functional Safety: Safety Instrumented Systems for the Process Industries).

The LOPA approach is based on the same risk assessment fundamentals ABS Consulting personnel have been using for three decades. We take these risk assessment fundamentals and apply them to help private industry and government clients make risk-informed decisions. Our primary LOPA instructor is a coauthor of the Center for Chemical Process Safety’s book, Layer of Protection Analysis, A Simplified Process Risk Assessment.

ABS Consulting's LOPA experts can team with your staff or work independently to provide any of the services listed below. We will review your goals at the beginning of the project to ensure that the analysis provides information of sufficient relevance, precision, and certainty to meet your decision-making needs.

Key Questions for Protection Layers:

* How safe is safe enough?
* How many protection layers are needed?
* How much risk reduction should each layer provide?



LOPA answers the key questions about the number and strength of protection layers by:

* Providing rational, semi-quantitative, risk-based answers
* Reducing emotionalism
* Providing clarity and consistency
* Documenting the basis of the decision
* Facilitating understanding among plant personnel




Layers of Defense Against a Possible Accident


ABS Consulting LOPA Services

Risk Judgement Fundamentals
A company should focus its resources on its highest risk scenarios. We work with companies around the world to use risk acceptance criteria and risk judgment tools to decide (1) which scenarios pose the greatest risk and (2) whether the current risk is acceptable.

Risk Acceptance Criteria
ABS Consulting can help your company establish acceptable risk criteria. Criteria in a risk matrix can be applied during (1) reviews of new designs, (2) management of change, (3) hazard reviews of existing systems, and (4) resolutions of recommendations.

Risk Judgement Techniques
To judge the residual risk of a scenario, we use qualitative, semiquantitative, and quantitative approaches for combining (1) the consequence of a scenario, (2) the likelihood of an initiating event, and (3) the effectiveness of the safeguards. These tools are used to rationally determine whether your layers of defense against a potential accident are acceptable or if additional/improved safeguards are needed.

Special Application of LOPA
LOPA can be used for any risk-based decision—it is particularly useful for deciding the integrity level necessary for safety interlocks. LOPA helps provide the basis for a clear, functional specification for an independent protection layer (IPL) (ANSI/ISA-84.00.01-2004, IEC 61511 Mod).




LOPA Process Diagram



Related Training

If you are interested in conducting LOPA studies on your own, our Training Services Division provides the best training services available on this and related topics. In addition, we offer training on our state-of-the-art, professionally developed software for documenting LOPA studies. The courses, which include "hands-on" practice sessions, give your personnel the resources and training necessary to conduct efficient and effective LOPA studies and related studies without outside assistance.

Featured Courses

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Layer of Protection Analysis (Course 209)
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Practical Application of SIL Evaluations (Course 210)
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Process Hazard Analysis Leader Training Using the HAZOP & What-If/Checklist Techniques (Course 103)
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Updating & Revalidating Process Hazard Analyses (Course 112)
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Advanced PHA Leader Techniques (Course 104)

Sumber :
http://www.absconsulting.com/svc_opRisk_LOPA.html