A 'bow-tie' is a diagram help us understand the risk you are dealing with in just one, easy to understand the picture. The diagram is shaped like a bow-tie, creating a clear differentiation between proactive and reactive risk management.
It’s just not enough to identify risks and they need to be managed: analysed, evaluated, monitored and communicated. Bow-Tie is a scenario-based risk management tool which helps PSM to accomplish these tasks and to answer questions like: “Where we are most exposed to risk?”, “do we have enough (or too many!) safety measures in place?”, “are our safety measures actually performing the way we intend?”
The bowtie method is a risk assessment method that can be used to analyse and communicate how high-risk scenarios develop..
What are the benefits of conducting Bow-Tie Analysis?
The benefits of the Bow-Tie analysis include, but not limited to:
- Provide a structure to systematically analyse a hazard.
- Help make a decision whether the current level of control is sufficient (or, for those who are familiar with the concept, whether risks are As Low As Reasonably Practicable or ALARP).
- Help identify where and how investing resources would have the greatest impact.
- Increase risk communication and awareness.
When HAZID should be done?
Bowties are risk assessment diagrams that provide a qualitative visual diagram to increase understanding of a risk. If you’re looking for a quick scan of all your risks, a HAZID might be more suitable. If you’re looking for a purely quantitative model, QRA might be more suited. Bowtie is really useful in most other risk assessment areas. It’s meant to structure a brainstorm session with multiple disciplines and get a result that everyone can understand without going through a thick report. If this sounds like something you’re looking for, keep reading.
Approach / Methodology
The purpose of the bowtie diagram is to gain insight in complex processes through oversight. This objective is always leading and can therefore overrule the guidelines if necessary. The intention to be analytically correct almost never outweighs the objective to keep an understandable diagram.
There are eight basic steps in building a bowtie diagram. They are as follows:
- Identify hazard:- The first step in managing risks is to identify what their sources are.
- Identify top event :-When we know what is potentially hazardous, we need to know how we could lose control over it.
- Identify threats :- Next we need to consider the scenarios or events which could directly cause the occurrence of the top event.
- Evaluate consequences :-After the top event occurs, subsequent scenarios or events are now possible. These consequences can lead to losses and damage.
- Identify preventive barriers:- The next step is to identify the barriers which should prevent the threats from reaching or causing the top event. These are preventative barriers.
- Identify recovery barriers :-Barriers on the right side try to recover from the occurrence of the top event. These barriers should prevent or mitigate the consequences and/or the resulting losses and damage
- Identify escalation factors:- The next step is to identify the specific situations or conditions under which the barriers are less or not effective.
- Identify escalation factor barriers :-The last step is to look at what barriers you have to prevent or manage these escalation factors.
Now with the escalation factors in place, our complete diagram is as follows:
Figure: Complete Bow-tie Diagram
Now the diagram can be completed with more information over each barrier:
- Determining the barrier type.
- Which parts of the management system support the barrier, such as procedures, policies, standards, etc?
- Who is responsible for the correct functioning of each barrier?
- Assessing barrier effectiveness.
This study is not done by one person, but a team. Assembling a competent team is one of the hallmark for a successful study.
This team will include:
- Design consultant / Project Manager
- Production Manager
- Chemical engineer / Chemist
- Maintenance Manager
- Electrical Engineer
- Instrument Engineer
- Quality Control Engineer
- HSE Representative, etc.
Within the team, a lead facilitator should be nominated to lead the study. The lead facilitator should be a competent and experienced person in the conduct of the Bow-tie study.
BowTie XP is the most used risk assessment software that is based on the bowtie method..
- Bow-Tie ToR
- Bow-Tie Worksheets
- Bow-Tie Analysis Report
Typical List of Bow-tie for the project
iFluids Engineering helps to provide the right solution and necessary recommendation with results for the precise decision for your Bow-Tie Analysis studies…