Bow Tie Analysis Service, Qatar

What is a Bow Tie Analysis

Bow Tie Analysis is to provide a holistic overview of how each Major Accident Hazard (MAH) scenario is managed and also to propose recommendations for identified inadequacies and demonstrate ALARP. The Bow Tie exercise intends to develop detailed/comprehensive Bow Tie diagrams which are to be dynamic and can be regularly maintained by assets to reflect the live status of each barrier condition. A Bow Tie diagram is a vital tool for communicating how control over major accident hazards is attained.

What is the Purpose of Bowtie analysis?

Bow Tie Analysis is an effective method for pinpointing areas where additional or improved controls could be beneficial. It plays a crucial role in risk treatment planning, especially in high-risk environments or when existing controls are deemed ineffective. By focusing on both preventing threats and mitigating consequences, this technique ensures that any gaps in control measures are identified and addressed efficiently.

• The Bow Tie analysis will include a Bow Tie diagram, for “each MAH scenario” presenting its causes (threats), consequences, and potential escalation scenarios, along with the barriers that prevent, control, or mitigate the scenarios.
• The barriers shall be further analyzed for their defeat mechanism (called escalation factors) and corresponding measures provided to overcome the barrier defeat mechanism (called escalation factor controls).
• The MAH scenario shall encompass both process MAHs and other MAHs applicable to the facility. The process of creating a Bow Tie is accomplished by organizing a Bow Tie workshop.
• It is important before the workshop to establish the scope and the context under which the bow ties shall be developed.
• MAH identification will be done by referring to HAZID, HAZOP, LOPA / SIL, QRA, and SIMOP, where MAH identification was already carried out, and include those identified MAHs into the facility MAH risk register.
• Barrier type identifies the operating characteristic of a barrier. While several classifications might be possible, as a sample it is suggested to use five types as below

Active Human	The barrier consists of human actions, often interacting with technology.
Active Hardware	All elements of the barrier are executed by technology.
Active Hardware – Human	It is a combination of Human behavior and technological proceedings.
Continuous Hardware	The barrier is always operating.
Passive Hardware	It works by virtue of its presence

• Each valid barrier should be auditable, independent, effective, and have the capability to completely abstain from the threat of migrating to the top event or, if a mitigation barrier, significantly decrease or eliminate the consequence.
• Each barrier should be independent of another barrier on the pathway and threat.
• Barrier can itself fully address the Threat or Consequence only if it complies with all the three following rules

Categorization of Nine Types of Barriers in Bow Tie Analysis

Safety Critical Equipment	SCE are any part of the installation, whose failure will either cause or contribute to a major accident, or the purpose of which is to avert the effect of a Major accident.
Safety Critical Task	SCTs should also be identified as part of defined activities in the MAH management process or human intervention as a step in a procedure that if not executed as defined would directly top event into consequence.
Procedural	Apart from operations SOP all other procedures fall under procedural category
Design	Barriers that involve training/ competency building.
Asset Integrity	Barriers that involves training/ competency building.
Training	Barriers that prevent the failure/ breakdown of equipment /system.
Operations	Apart from operations SOP all other procedures fall under the procedural category
Maintenance	Items directly under the maintenance purview will be considered as “Maintenance” category
Others	Items considered during initial stages of design

• The following Sample color coding shall be followed when identifying the barriers to ensure the uniformity of depicting a barrier to assist users in recognizing a particular barrier in Bow Tie.
  • The below Sample figure shows barrier color codes.

A Qualitative ALARP demonstration will be done in the Bow Tie workshop to ensure that preventive & mitigation barriers are in place for each MAH. All the existing barriers both preventive & mitigation shall be identified even if criteria for the minimum number of barriers have been met.

The ALARP demonstration shall be done for all recommendations identified in the Bow Tie workshop. For recommendations, that do not come under the broadly acceptable region of the risk tolerability criteria or ALARP (As low as reasonably practicable) region will follow a hierarchical approach for identification of additional risk reduction initiatives where it is essential as a role of  ALARP demonstration:

• Eliminate, to physically remove the hazard
• Alternatives to replace the hazard with a less hazardous substitute
• Closeting from Hazard by distance or isolation
• Prevention by engineering e.g. process detection, ESD depressurization
• Mitigation by engineering e.g. Fire and Gas Detection, and active/passive fire protection.
• Prevention/mitigation by organization e.g. manning, training, procedures
• Mitigation by intervention e.g. emergency response, maintenance
• Personal protective equipment.

The general focus of Bow Tie is managing Major Accident Hazards, as working personnel need to understand how these may occur and the barriers and escalation factor controls deployed to prevent them.

Bow Tie Analysis diagrams shall be unit-level / equipment-specific MAH scenarios. A Bow Tie diagram shall be prepared for each MAH scenario, presenting its causes, consequences, and potential escalation scenarios, along with the barriers that prevent, detect, control, or mitigate the scenarios (either a preventative barrier or a mitigating barrier). The barriers will be further analyzed for their defeat mechanism (escalation factors) and measures provided to overcome the barrier defeat mechanism (escalation factor controls).

Key Elements in Developing Bow Tie Analysis

• Hazard
  • A Hazard refers to an operation, activity, or material that possesses the potential to cause harm.
  • The Hazard plays a crucial role in delineating the extent of the entire bow tie.
  • Hazards that are too general can result in generic bow ties, which is why it is important to identify and address specific hazards.
  • This practice is known to enhance the value as it elevates the level of intricacy in the remaining part of the bow tie.
• Top event
  • The top event occurs when there is a loss of control over the hazard or its containment, resulting in the release of its harmful potential elements.
• Consequence
  • Consequence refers to adverse outcomes that may arise from a given event, potentially resulting in harm or damage.
• Threat
  • Threats have the potential to cause a loss of control over a hazard, which can ultimately result in the occurrence of the top event.
• Barrier (Prevention and mitigation)
  • Barriers are present on the primary routes (posing a risk to the top event or from the top event to the consequence).
  • Barriers must have the capability on their own to prevent or mitigate a Bow Tie sequence and meet all the rule sets/validity requirements for a barrier to be effective, independent, and auditable.
• Escalation Factor
  • An Escalation Factor can apply to barriers on either side of the Bow Tie diagram.
  • For lucidity of visual appeal, often they glide from the left on the prevention side, and from the right on the consequence side, but they are the same in all aspects.
• Escalation Factor Control
  • Controls along the Escalation Factor pathway are called Escalation Factor Controls.
  • The Escalation Factor is a condition that can reduce the effectiveness of the barrier to which it is attached.
  • An escalation factor does not directly cause a top event or consequence, but since it degrades the main pathway barrier, the likelihood of reaching undesired consequences will be higher.

Bow-Tie workshop

Bow Tie structure shall be developed before the Bow Tie workshop and also assimilate all the relevant details of the technical site survey carried out along with the existing barrier condition & barrier effectiveness. Typically, there is the recurrence of preventive barriers amidst different bow ties and very often absolute duplication of mitigation barriers. Bow Tie development is to be carried out using the typical steps as shown below.

It’s not likely that the Bow Tie will be correct as developed in the workshop. The workshop focuses on using time with experts in the team to capture their experience of the barriers in use rather than whether the structure of the diagram is the same – this can be rectified in post-workshop tasks. The following approach will be used for the execution of the development of Bow tie, The flowchart below shows a workshop iteration loop.

Steps for Executing the Development of Bow Tie Analysis

The following approach will be used for the execution of the development of Bow-tie,

• Identify the hazard and a top event
• Prepare Bow Tie diagrams using appropriate software, as indicated above. Consideration will be given to pre-constructing Bow Tie diagrams to improve efficiency in the workshop.
• Identify threats, consequences, and barriers for each top event.
• Identify preventive barrier
• Identify mitigative barrier
• Identify escalation factors and escalation factor controls.
• Identify critical tasks that maintain the performance of the barriers or escalation factor controls
• Determine if additional barriers are required to reduce risks to as low as reasonably practicable (ALARP).
• Identify the barriers and escalation factor controls including identification of MAH critical elements (MCEs) and tasks (MCTs).
• All identified barriers and their escalation factor controls (both preventative and mitigation) required to meet qualitative ALARP criteria of minimum numbers will be qualified as MCEs and/or MCTs related to critical procedures.
• The Bow Tie analysis approach should then be repeated for all identified hazard /top event combinations.

Workshop team

• Bow Tie Analysis is conducted within a workshop involving all key stakeholders including appropriate discipline Engineers and facilitated by an independent Facilitator, along with a Scribe.
• Core Team shall consist of:
  • Project/Operations in-charge
  • Operations Representative
  • Maintenance Representative
  • Process Engineer (or equivalent)
  • Instrumentation Engineer (or equivalent)
  • Technical HSE Engineer (or equivalent)
• The non-Core Team shall include the following:
  • Specialist Engineering Representatives
  • Regional/Operational HSE Representative (or equivalent)
  • Corporate HSE&Q Representative

Report

• The Report contains the Bow-Tie Analysis diagram & all the findings of the Bow-Tie workshop, including recommendations/safeguards, action tracking including a target for the completion date, etc.
• The Report will be prepared for each production facility/station / operating unit/equipment-specific MAH scenario so that the identified and listed safeguards are not generic but very specific to the MAH scenario under consideration.
• The identified inadequacies and recommendations must be captured in the report. A criticality ranking of all recommendations from a risk-based perspective shall be done.
• The recommendations will be mapped against the relevant CCPS PSM element(s) as shown below.

For traceability, the outcomes from meetings, workshop sessions, group sessions, and agreements must be recorded in the MOM Which shall be finalized and signed by all parties participating in the Bow-Tie workshop.  Prepare an Excel-based live action tracking workbook for all the generated actions that can be periodically updated and also log any discrepancy noted in the operations, drawings / technical documents.

Conclusion

Bow Tie Analysis is a valuable risk assessment tool for identifying and managing potential hazards and their consequences. By visually representing the relationships between threats, controls, and consequences, it enables organizations to develop more effective risk treatment plans. It helps to assess control effectiveness, identify gaps in risk management, and enhance decision-making processes. This systematic approach is essential for industries dealing with high-risk scenarios, ensuring that robust mitigation strategies are in place to protect operations, employees, and assets.