LOPA (Layer of Protection Analysis) – The Semi-Quantitative Approach to Risk Assessment Course 11 (2-Day) | Process Improvement Institute

Learn from the co-originator of LOPA who is also the primary author of the LOPA textbook (2001) and Guidelines for Independent Protection Layers and Initiating Events (2012).

Are proposed or existing combinations of safeguards enough to prevent an accident or mitigate the consequences? Do you perceive that doing a fully quantitative risk assessment (QRA) would be over-working the problem? Then LOPA (Layer of Protection Analysis) is the new tool you need to learn.

LOPA combines both qualitative and quantitative elements of hazard evaluation and risk assessment to analyze and judge the adequacy of existing or proposed safeguards against process deviations and accident scenarios. It uses an order of magnitude approach to quantify the likelihood of causes, likelihood of failure of independent protection layers (IPLs), and estimate the consequences for chosen accident scenarios. These approximations are used to estimate the risk of a scenario.

A key to the success of LOPA is its rules for judging if protection layers are truly independent. Because of these rules, LOPA helps the analysts make consistent judgments of if the risk of scenarios are “as low as reasonably practical (ALARP)”. This “How To” course is taught by one of the principal authors of the AIChE/CCPS book, Layer of Protection Analysis (2001). The course covers all aspects of how to apply this very useful technique. Workshops are used as the primary mode of teaching each aspect of LOPA. You will perform several complete LOPA before leaving class.

Recommended prerequisites: Attendees should have strong technical skills and prior training in qualitative hazard evaluation techniques; prior completion of Course 8: Process Hazards Analysis Leadership or equivalent is highly recommended.

What You Will Learn:

  • When and how to use LOPA.
  • How to identify which scenarios from a HAZOP or other qualitative analysis could benefit from LOPA
  • How to systematically create risk scenarios for new processes or for existing processes under change
  • How to establish risk acceptance (risk tolerance) criteria for use within your company (this is also called development of ALARP criteria) and how to depict this in a Risk Matrix or in a formula
  • How to calculate “as-is” risk for a cause-consequence pair:
    • How to estimate the frequency of the initiating event
    • How to determine the consequence for the scenario (unmitigated)
  • Understand what is meant by “independence” and “uniqueness” with respect to the safeguard layers (IPLs)
  • How to calculate the value of each IPL
  • How to determine the risk of a LOPA scenario and how to determine how much further risk reduction (if any) is necessary
  • How to use LOPA to determine the Safety Integrity Level (SIL) necessary for an instrument IPL (to comply with the requirements of IEC 61508/61511 for safety instrumented systems)
  • How to document LOPA
  • How other companies worldwide use LOPA to:
    • Decide which PHA/HAZOP recommendations to reject and which to accept
    • Focus limited resources within mechanical integrity departments and operations on what is critical to manage risk to ALARP
    • Avoid wasting resources on the added cost and unproductive sophistication that often occurs when they instead quantify risk using QRA methods such as fault tree and event tree analysis
    • Perform specialized risk modeling for facility siting questions

Take Home:

  • Comprehensive course notebook containing
    • Examples of risk acceptance and judgment protocols
    • Industry examples and solutions to all LOPA workshops
  • Certificate of Completion
  • 1.4 CEUs & 1.4 COCs

Typical Course Candidates

This course is designed for experienced PHA/HAZOP leaders and builds on risk judgment skills learned while doing qualitative risk reviews. However, others who do qualitative, semi-quantitative, and fully quantitative risk assessments will benefit from learning this quicker, simpler method for estimating risk. Only individuals with a strong technical background (such as engineers and scientists) should attend. Others who may benefit from this course include:

  • Managers – Operations, Safety
  • Project Managers
  • Engineers – Process, Safety, and Mechanical
  • PSM Coordinators and Managers

Course Outline


Day 1 (8:00 a.m. to 5:00 p.m.)

Introduction to LOPA

  • Learning objectives and goals of using the LOPA technique
  • What is LOPA? How is LOPA applied? Definitions
  • Where does LOPA fit with other hazard evaluation and risk assessment methods?

Developing LOPA Scenarios

  • Selecting candidate scenarios from qualitative (brainstorming) hazard evaluations
  • Scenarios from design questions and from incidents
  • Deciding on the right cause-consequence pair to define each scenario

Estimating the Consequence of the Scenario

  • Using a look-up table of consequence
  • Developing a consequence look-up table for your company
  • Alternative methods for estimating consequences
  • Workshop 1: Estimating the consequence of a scenario (part of a continuing example)

Estimating the Likelihood of the Selected Initiating Event

  • Using a look-up table of initiating event categories and frequencies that has been updated based on the recent guideline (2012)
  • How to develop an initiating event look-up table for your company
  • Addressing enabling conditions and time-dependent initiating events
  • Workshop 1: Estimating the frequency of an initiating event of a scenario (part of a continuing example)

Estimating the Probability of Failure of Independent Protection Layers

  • Definitions, rules, and exceptions for giving credit for an independent protection layer (IPL)
  • Using a look-up table of IPL categories and probability of failure on demand (PFD) that has been updated based on the recent guideline (2012)
  • How to develop an IPL look-up table for your company
  • Workshop 1: Deciding which safeguards are valid IPLs and estimating the PFD of the valid IPLs (part of a continuing example)

Calculating the Risk

  • Using a standardized LOPA worksheet
  • Rules for calculating risk for an individual scenario (LOPA)
  • Rules for summing risk of related scenarios (for special applications)
  • Workshop 1: Calculating the risk of a LOPA scenario (part of a continuing example)

Day 2 (8:00 a.m. to 3:30 p.m.)

Judging the Risk

  • Examples of risk tolerance criteria from the industry
  • Development and implementation of a company risk tolerance criteria (and possible liability issues related to documenting a risk tolerance criteria)
  • Workshop 1: Judging the risk of a LOPA scenario (part of a continuing example)

Case Studies

  • Workshop 2: Performing a LOPA from beginning to end, given a LOPA scenario
  • Workshop 3: Performing several LOPA, beginning with a set to HAZOP tables and deciding which scenarios need LOPA

Special Applications of LOPA

  • Using LOPA for facility siting questions
  • Using LOPA to select the SIL for a safety interlock
  • Workshop 4: Estimating the composite risk for facility siting risk assessment

Planning your path forward with LOPA

More Information


Bill BridgesBill Bridges will be the instructor for this course. He has taught this course many times to hundreds of analysts. He was one of the inventors and first implementers and trainers of LOPA. He wrote one of the first definitive papers of the topic and he co-chaired (with Art Dowell III of Rohm & Haas Chemical Company) the International PSM conference (sponsored by AIChE/CCPS) that introduced LOPA. He was a principal author of the CCPS textbook on this topic and he developed the first course on this topic with experts at ARCO/Lyondell (in 1996). He has performed dozens of LOPA in real plant settings and is considered one of the few experts on this topic. He is also the primary author of the follow-on textbook, Guidelines for Independent Protection layers and Initiating Events, 2012 (CCPS/AIChE). To find our more about this course or to check into having this course taught at your site; contact Mr. Bridges at 1.865.675.3458 or by e-mail at wbridges@p-i-i-i.com.


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This course can also be taught (either as-is or customized) at your site. Please contact PII for details about having our training provided at your site.

Pricing for Public Offerings (per student):

$1,100.00 USD (for 2-day version in USA)

$1,495.00 USD (for 2-day version in Dubai, UAE)

Registration Information:

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