Perform risk assessments using the bowtie method or LOPA (Layer of Protection Analysis) tables: GRIF Risk – Risk Analysis Software

Bowtie diagrams are entered via an intuitive graphical interface of the GRIF Risk module, a risk analysis software, which is easy to use. Initiating events can be entered quickly, and users can specify the frequency of occurrence, final events and their related level of criticality, as well as the barriers whose failure is defined according to the many laws available.

In the lower section, data can be input into a LOPA table. In this case, a scenario is created by entering the undesirable event (existing or new), the initial cause and the different barriers included in the protective measures. A bowtie model is created and automatically formatted in the data entry zone.

The ALBIZIA calculation engine developed by TotalEnergies produces a wide range of results:

• Instantaneous and average frequencies for all scenarios.
• Barrier demand frequency.
• PFD (Probability of Failure on Demand) and PFH (Probability of Failure per Hour) of barriers, which are specified in detail (periodic test, SIL loop, etc.).
• Risk Reduction Factor required to remain within an acceptable risk zone.
• Importance factors (including Barlow-Proschan) to identify the barriers that need to be improved.

• Multiple risks
  • Several risk matrices can be defined, such as Safety, Assets or Environment risk matrices. Each matrix is assigned a criticality level: moderate, serious, major, etc. The criticality thresholds and frequency limits can be configured.
  • o For each scenario, a risk is recorded on each matrix. A scenario can be qualified as catastrophic in terms of human risk but moderate in terms of financial risk and vice versa.
    

• Models: do you regularly conduct studies using the same safety barriers and the same risk matrices? With GRIF Risk, you can create models with a specific number of pre-configured barriers and risk matrices.
• A posteriori mean: many software applications multiply the average frequency of the initial event   by the average failure probability for each barrier   to calculate the frequency of a scenario.
  • The formula shown below is imprecise and non-conservative: 
  • In contrast, the Risk module calculates an average over [0,T] of frequency w for a Boolean formula:    
    
    This approach, combined with the use of BDDs, represents the cutting-edge in scenario frequency calculations.

• Input data is summarized in tables making it easier to check the quality of an entry.
• Option to automate calculations (batch runs) and draw variations for sensitivity analysis.
• Results are stored in the document and can be exported in a variety of formats (csv, XML, Excel, etc.).
• Results can be viewed as line graphs, pie charts or histograms.
• Printing in PDF vector format produces high-quality images and the files are small enough to be sent by email, even if the document contains hundreds of pages.
• External files (PDF certificates, system images, etc.) can be added to the document and incorporated into the full report.
• Interaction with the operating system: option to copy/paste either to or from word processing software, spreadsheets, or presentation tools.

Bow-tie diagrams created in Risk can interact with any model of GRIF Boolean package: Fault Trees, Reliability Block Diagrams, SIS, etc. As a result, barriers or initiating events can be described in detail and the dependencies between barriers, which may have certain components in common, can be taken into account.

Once the Risk module has indicated the required Reduction Factor, a Safety Instrumented Loop can be added from the SIL module to the bowtie model via the Bool module. This approach ensures that the loop achieves the required PFD/PFH and confirms that the new frequency for each scenario is in an acceptable range.

In addition, the Safety Requirement Specification system helps users to comply with IEC-61508 or any other standards for which defining requirements is essential.