LOPA Generic Enabling Events
LOPA Generic Enabling Events are predefined probability values used during a Layer of Protection Analysis (LOPA) to represent conditions that must exist for a hazardous consequence to occur. Standardising these values helps organisations perform more accurate risk calculations while ensuring consistency across every LOPA study.
Within SLM, Generic Enabling Events can be managed centrally at either the Enterprise or Site level before being reused throughout HAZOP and LOPA studies. This reduces facilitation time, eliminates inconsistent probability values and improves the quality of risk assessments across multiple facilities.
This guide explains how to create, manage and apply LOPA Generic Enabling Events within SLM, including Enterprise and Site configuration, synchronisation between locations and their application during HAZOP and LOPA studies.
What Are LOPA Generic Enabling Events?
LOPA Generic Enabling Events are predefined probability values that represent conditions which must exist for a hazardous scenario to progress from an initiating event to an unwanted consequence. Although they do not directly cause the hazard, they influence the overall risk calculation and are an important part of a Layer of Protection Analysis (LOPA).
Rather than estimating these probabilities during every workshop, SLM allows organisations to create a library of approved enabling events that can be reused across multiple studies. This improves consistency, reduces facilitation time and ensures company-approved values are applied throughout the organisation.
- Standardise enabling event probability values.
- Improve consistency across LOPA studies.
- Reduce manual calculations and transcription errors.
- Support repeatable risk assessments.
- Increase confidence in scenario calculations.
For an overview of the complete LOPA methodology, see our LOPA Facilitation Guide. Organisations using the MSS LOPA Module can centrally manage enabling events alongside other LOPA reference data.
Creating Generic Enabling Event Libraries
SLM enables organisations to create centrally managed libraries of Generic Enabling Events within the Global Module. Each enabling event includes a description together with predefined probability values for the applicable consequence categories.
These libraries can be maintained at either the Enterprise or Site level depending on whether the organisation uses company-wide standards or site-specific probability values.
- Enterprise level – use when enabling events are standard across every site.
- Site level – use when facilities require their own approved probability values.
Enterprise libraries can also be synchronised to Sites, allowing approved enabling events to be distributed throughout the organisation while maintaining central governance.
Learn more about enterprise configuration in the System Module Global Configuration guide.
Applying Generic Enabling Events During Studies
Once Generic Enabling Events have been configured, they can be applied directly within both HAZOP and LOPA studies. Users simply select the required scenario, review the available global enabling events and copy the appropriate values into the assessment.
This eliminates the need to recreate enabling events for every study while ensuring approved company standards are used consistently.
- Select the applicable enabling events.
- Copy approved values into the scenario.
- Apply probabilities during the LOPA calculation.
- Maintain consistent documentation across studies.
The same workflow is available within both the HAZOP Module and Local Module worksheets, giving facilitators a consistent process regardless of where the analysis is performed.
Enterprise or Site Configuration?
SLM provides flexibility by allowing Generic Enabling Events to be managed at either the Enterprise or Site level.
Enterprise configuration is recommended when enabling event probabilities are common across every facility. Site-level configuration allows individual locations to maintain their own approved probability values where operational differences exist.
Synchronisation tools make it easy to distribute Enterprise libraries to Sites while maintaining consistency across the organisation.
Benefits of Standardising Enabling Events
Using centrally managed Generic Enabling Events provides significant advantages for organisations performing Layer of Protection Analysis.
- Improve consistency between facilitators.
- Reduce manual calculations.
- Eliminate transcription errors.
- Support corporate governance.
- Produce repeatable LOPA calculations.
- Improve audit readiness.
Standardised enabling event libraries also simplify training and help ensure every assessment follows the same approved methodology.
Related LOPA Resources
Continue learning about Layer of Protection Analysis with these related resources:
For additional guidance on Layer of Protection Analysis and risk assessment best practices, visit the AIChE Center for Chemical Process Safety (CCPS).
