In this article:
Bowtie workshops look simple, but they can go wrong with many hours spent and misleading results if not adequately planned and executed.
Pre-workshop planning and post-workshop processing are more critical for bow tie workshops than other types of Process Hazard Analysis (PHA) workshops. This is to ensure good results and effective resource utilization. This article discusses essential steps in bow tie workshops.
Scope and Context
It is essential to establish the scope and context for the bowties before the workshop. A non-exhaustive list of relevant questions in this regard includes:
Who is the intended audience (end-user)?
What is the study scope, e.g., only process safety Major Accident Hazards (MAHs)? Whole plant or unit? Need to capture metadata?
What is the purpose of bowtie, e.g., training or design review?
How many scenarios (top events) will be studied?
Consequences to be assessed, e.g., personnel, environment, asset, and/or other?
It is recommended to go for quality, NOT quantity when defining the number of scenarios to consider. Besides, metadata's inclusion should primarily be considered when the audience (end-user) has access to the bow tie software.
Workshop Planning
Workshop planning should be documented in a Terms of Reference (ToR) for the workshop. The workshop planning process should include i.a.:
Prepare simplified draft bowties ahead of the workshop;
Collect basis material (Process Flow Diagrams, PHAs, existing bow ties, Piping & Instrumentation Diagrams, etc.);
Lessons learned from accidents and near-miss reports, incident investigations, audits, etc.
Workshop Team
An experienced facilitator and scribe team is essential;
Subject matter experts relevant for a bow tie in question (Operations, Maintenance, Design);
Workshop team members shall be familiar with the bow tie methodology;
Consider a short training session in the bow tie methodology ahead of the workshop.
Workshop Sequence
It is recommended that the workshop follows the following sequence:
Identify hazards and top events;
Identify consequences;
Identify threats;
Identify prevention barriers;
Identify mitigation barriers;
Identify degradation factors and degradation controls (if part of the scope);
Add metadata for barriers and degradation controls (if part of the scope);
Review bow tie for completeness and quality.
Note that the main building blocks of the bowties should, to the extent possible, be included in the draft bowties prepared in advance of the workshop.
Post-Workshop
It is unlikely that the bowtie will be utterly correct as generated in the workshop. The workshop's focus should be to use the time with the subject matter experts' experience with the barriers rather than on whether the bowtie structure is correct. Hence the bowties will need corrections and populating blanks after the workshop. When the bowties have been tidied up, an experienced bowtie specialist should conduct a formal quality review, not part of the workshop.
ORS Consulting has supported clients in multiple industries with bow tie assessments. Contact us if you would like to discuss how to use bow tie models for managing major accident hazards.
