Layer of Protection Analysis (LOPA)
ABS Consulting's LOPA approach provides companies with 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 approach is based upon risk assessment fundamentals used by ABS Consulting personnel for over thirty years. We apply these fundamentals to help private industry and government clients make informed risk management decisions.
ABS Consulting LOPA Services
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 confirm that the analysis provides information of sufficient relevance, precision and certainty to meet your decision-making needs.
- Risk judgment acceptance criteria and tools
- Risk acceptance criteria
- Risk judgment techniques
- Special Application of LOPA for an independent protection layer (ANSI/ISA-84.00.01-2004, IEC 61511 Mod)
ABS Consulting Approach to Layer of Protection Analysis (LOPA)
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). LOPA results support:
- Assigning priorities to recommendations
- Developing safety requirement specifications for safety instrumented systems, which is a necessary step in complying with ANSI/ISA-84.00.01-2004, Functional Safety: Safety Instrumented Systems for the Process Industries
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) according to the requirements of standards such as ANSI/ISA-84.00.01.
LOPA Process Diagram
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 for the decision
- Facilitating understanding among plant personnel
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