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Layer of Protection Analysis (LOPA)

Layer of Protection Analysis

ABS Group's 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 Layer of Protection Analysis (LOPA) to be a cost-effective addition to PHA revalidations and also an important tool for ALARP demonstration. Our approach is based on risk assessment fundamentals used by ABS Group personnel for over 30 years. We apply these fundamentals to help private industry and government clients make informed risk management decisions.

Our experts can team up with your staff or work independently to 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. Our LOPA services include:

  • Safety Barrier Identification
  • Safety Objective Analysis (SOA)
  • Probability of Failure on Demand Determination
  • Layers of Protection Analysis
  • Safety Integrity Level (SIL) Determination
  • Risk Acceptance Criteria
  • Risk Judgment Techniques
  • Special Application of LOPA for an Independent Protection Layer (ANSI/ISA-84.00.01-2004, IEC 61511 Mod)

LOPA Overview

LOPA is the newest 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, or HAZOP, analysis and what-if analysis) and the quantitative end (characterized by methods using fault trees and event trees). LOPA helps the analyst make consistent decisions on the adequacy of existing or proposed layers of protection against an accident scenario. The technique is ideally suited for companies striving to meet specific risk targets or to lower risk as low as reasonably practicable (ALARP).

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 SIL of your safety instrumented system (SIS) according to the requirements of standards such as ANSI/ISA-84.00.01.

PHA Revalidation

The PHA revalidation process may involve a complete re-do of the PHA on the asset due to the significant number of changes that have occurred over time or the poor quality/deficiencies of previous PHAs. Or a revalidation may only involve an updating of the previous PHA to address changes and incidents that have occurred since the last study and to verify that previous results are still accurate. ABS Group can help you identify the best approach to revalidate your PHA. In our revalidation process, we will address:

  • Modifications made to the process
  • Previous incidents
  • Status/resolution of previous recommendations
  • Human factors and/or facility siting/stationary source siting analysis
  • Hazards of non-routine operations
  • Compliance to requirements within applicable regulations, industry standards and internal company requirements

Leveraging the experience gained from performing hundreds of PHA Revalidations, we have developed a streamlined process and checklists to help expedite the revalidation effort.

HAZOP Analysis

A HAZOP study is used to verify the integrity of design or procedures with respect to safety and operability. Our global engineers have extensive experience conducting HAZOP analyses and investigating how systems or facilities deviate from the design intent and create risk for personnel and equipment. HAZOPs have been used with great success within the Oil, Gas and Chemical sector to maintain safer, more efficient and more reliable assets and operations, and these studies have become a standard in the design of offshore process systems.


What-if analysis is a brainstorming approach that uses broad, loosely structured questioning to postulate potential upsets that may result in accidents or system performance problems. Using this approach can help you confirm that the appropriate safeguards against those problems are in place. Our multidisciplinary engineers understand the procedure for performing what-if analysis to identify various system hazards.


Understanding and addressing failure modes and their subsequent effects and criticality (including probability of occurrence and degree of severity) significantly reduces nonproductive time and safety-related incidents. We have experienced personnel combined with proven processes and systems to deliver mission-critical failure mode, effects and criticality analysis (FMECA) services. We do so by leveraging years of field experience coupled with our software, automation and project management expertise to help you identify potential failure modes for control systems, equipment, automation components and more.

Hazard Identification

If a hazard is not identified, its contribution to the risk cannot be estimated. Only those hazards that are identified are likely to be controlled with any confidence. Our experienced engineers can assist in the identification and analysis of hazards for HAZOP and hazard identification (HAZID) studies in the Marine and Offshore, Oil, Gas and Chemical, Power and Government sectors.

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