Bowtie Diagram Assessments

Bowtie diagrams can be used as a Process Safety Management tool used to visually display key major accident hazards (MAHs) showing what initiating causes could occur to cause the top event of the MAH and what preventative barriers are in place to ensure a major incident/accident doesn’t occur. It also displays the consequences which can occur from the top event and the mitigating barriers in place to reduce the severity and consequences after the top event of the MAH has taken place.

When to use Bowtie Diagrams?

The best time to use a bowtie diagram for process safety is after the Process Hazard Analysis (PHA) or HAZOP has been carried out to understand what the main major accident hazards (MAHs) and top events are and what barriers there are already in place. Once these have been plotted on the bowtie diagram it should be easier to visually see where the main gaps are within the preventative and mitigation barriers, and this will help the operations team see where to focus any investment or quick wins to improve the process safety of the process. Bowtie diagrams are a great communication tool for training operations staff as well as management/non-technical stakeholders to show visually where there are key gaps within the preventative and mitigation barriers for key major accident hazards (MAHs). It helps keep it simple for the operations team so they can see the whole process on one sheet and helps improve understanding of the process. They also allow the user to use them for incident investigation and learning from past events since it maps out the failure points in the system and allows the team to focus on the weaknesses which need to be addressed.

Finch’s Approach to Bowtie Diagrams

Finch employs a standard Bowtie Diagram tool which is a proven method for risk assessment and management of Major Accident Hazards (MAHs). This approach allowed us to visually map out the potential causes and consequences of identified hazards and to pinpoint critical prevention and mitigation measures required to keep the client safe. The following steps are carried out to ensure a great experience for Finch’s clients.

1. Gather information on the Major Accident Hazards (MAH)/Top Event for the site(s):

Determine the main Major/Accident Hazards (MAHs) found on site i.e. loss of containment from a flammable storage tank and determine the top events for each of these hazards.

2. Site Visits:

Explore each area looking for the major accident hazards with key personnel.

3. Construct the Bowtie Diagram:

Plot the Major Accident Hazards/Top event in the centre of the Bowtie diagram.
Plot the main causes of the event on left-hand side
Plot the preventative barriers between the causes and top event
Plot the consequences on the right-hand side

4. Determine the major gaps in preventative and mitigation barriers:

The use of colour coding can be used on the preventative and mitigation barriers (green for the barrier is present and red for the barrier not being present) which can help the user understand where the major gaps are within the barriers and whether there are any barriers for preventing certain causes or mitigating the consequences which need to be implemented.

5. Continuous support once the Bowtie Diagram is complete:

Finch supports the client with their actions/recommendations and provide suggestions on how to close the gaps and ensure their risks are managed effectively.

Typical industries Finch can support

The typical industries that undertake Bowtie diagrams are chemical, manufacturing, food & drink, mining, nuclear, oil & gas and pharmaceuticals to ensure their safety systems are as safe as possible and the risk of a high-risk event is as low as reasonably practicable (ALARP).

Outcome

The Bowtie Diagram provided is clear and easy to understand and visualise the risks and control measures associated with each of the Major accident hazards (MAHs) on site. By employing the Bowtie diagrams analysis, Finch Consulting enable the client to gain a thorough understanding of their risks and establish a strong basis of safety for major accident hazard prevention. This facilitates safer operations but also ensures they remain legally complaint typically under the COMAH regulations.