process risk and safety specialists

nuclear and radiation consultants


Bow-Tie Consulting offers a comprehensive range of risk and safety-related services, including:

Aviation Safety Management

As global air traffic increases, risk assessment within the aviation industry is becoming widely accepted as a valuable tool by both operators and regulators. Aviation risk focuses on demonstrating that acceptable risk levels are being achieved and maintained. The regulatory focus has also shifted from a prescriptive rule based approach to one where licence holders are required to demonstrate that their safety management system is well developed and delivering acceptable levels of safety.

Since 2005 Bow-Tie Consulting personnel have been utilising their extensive risk assessment experience and skills to assist Australian, New Zealand and European aviation operators and regulators in the development of Safety Management Systems and Risk assessment techniques. Safety projects undertaken have included:

  • The assessment of Safety Culture within a Regulatory Safety Research Group,
  • The development of Safety Management Frameworks,
  • Risk assessment of specific airspaces and airports
  • Safety case development for proposed new air traffic control concepts
  • Risk assessment of helicopter external load operations.

The key consulting services which we are able to offer within aviation include:

  • Hazard Identification
  • Qualitative and semi-quantitative Risk Assessment utilising the Bow-tie technique
  • Full Safety Case Preparation
  • Safety Management Assessment and Development
  • Safety Culture Assessment
  • Accident / Incident Investigation
  • Risk Assessment Training

Bow-Tie Consulting has also partnered with aviation management consultants to provide a highly experienced team to independently review airspace and airport safety from operational, risk and regulatory requirement perspectives.

Nuclear Safety Case Preparation

Bow-Tie Consulting personnel have significant Australian and international experience managing nuclear operations and supplying consulting services to the nuclear industry.  This has included work with operating reactors, supporting fuel cycle and waste services, radiopharmaceutical production, facility decommissioning, safety management assessment and development.  Being familiar with the industry, its safety and corresponding regulatory requirements, allows Bow-Tie Consulting to efficiently identify needs and assist operators with their projects.  Most recently in Australia, Bow-Tie Consulting personnel have assisted nuclear facility licence holders in achieving and maintaining their operating licences through the preparation of safety cases and associated Operating Limits, identifying Critical Controls and supporting their presentation to the regulator.  We have also assisted regulators in their assessment of radiological facilities meeting Major Hazard Facility classification.

When engaged to facilitate the development of a Safety Case, our preference is to work as an integral part of the operations / project team during the period of preparation.  This allows us to achieve a close working relationship with operators, engineers and managers and helps to efficiently steer the team through the process of hazard identification, risk assessment, design reviews and the generation of lifecycle safety management & verification requirements.  The facilitation of a transparent safety assessment process achieves a better understanding of safety requirements and their derivation amongst the operating team and hence ownership of the Safety Case.

The key consulting services we offer for the nuclear industry include:

  • Hazard Identification including HAZOP Facilitation
  • Bow-tie Analysis
  • Consequence Assessment: routine and accidental radiological exposure
  • Safety Integrity Level (SIL) Determination
  • Layers of Protection Analysis (LOPA)
  • Quantitative Risk Assessment (QRA)
  • Full Safety Case Preparation
  • Safety Culture Assessment
  • Safety Management Assessment and Development
  • Accident / Incident Investigation
  • Risk Assessment Training

Safety Integrity Level (SIL) Determination

The concept of safety integrity levels (SILs) was introduced to measure the quality or dependability of a system which has a safety function – a measure of the confidence with which the system can be expected to perform that function. Safety Instrumented Systems (SIS) are used in many systems for the prevention and mitigation of safety-related hazards.  A SIS may be made up of one or more Safety-Instrumented Functions (SIF).  The target Safety Integrity Level (SIL) of each safety-instrumented function (SIF) dictates the required performance of each SIF.  That performance criterion is determined via a SIL assessment.

SIL study is a structured and systematic examination by a multi-disciplinary team of design, operations, maintenance and management professionals. This team reviews each identified hazard and assigns a target SIL for each hazard. An approved technique is used, as defined in IEC 61508 / IEC 61511, and applied to all parts of a system to establish the minimum allowable SIL for each safety instrumented function in terms of Probability of Failure on Demand (PFD) so that safety and operability problems on the complete system are eventually identified and mitigated.

Bow-Tie Consulting will use the most appropriate methodology from IEC61511 in consultation with your requirements and have experience using all the following methods:

  • Quantitative method
  • Qualitative risk graph method
  • Qualitative hazardous event severity matrix method
  • Semi-quantitative method
  • Safety layer matrix method
  • Calibrated risk graph
  • Layer of protection analysis (LOPA) method

Our analysts have process knowledge as well as knowledge of instrumentation used in the development of SIL rated protection systems. This will ensure that the SIL allocation is done in awareness of the process hazards and the practicalities of the design of SIL protection of various ratings.

We hold a licence for exSILentia ™ which is one of the world recognised software systems with an integrated database of failure data. Our clients often are required to use this software when verifying that the SIL requirements are met by a particular design. We assist our clients in the design process by ensuring at an early stage in the design that the basic design can meet the SIL requirements.

Bow-Tie Analysis

Bow-tie diagrams clearly display the links between the potential causes, preventative and mitigative controls and consequences of a major accident. Bow-tie analyses can also be integrated with semi-quantitative analysis techniques such as Layers of Protection Analysis (LOPA).

We aid our clients in identifying their risks and examining their controls or safeguards through the preparation of Bow-Tie diagrams. Bow-Tie diagrams are excellent tools to display the causal sequences that could cause a risk to the business and are often used to present the outputs from other risk studies. Our experienced facilitators will ensure that the Bow-Tie diagrams are not excessively complex because this reduces the ability to be a visual representation of the risk being studied.

Bow-Tie Consulting’s experienced personnel will work with you to develop Bow-Tie diagrams that clearly represent the risks of your business and assist you to identify and assess the reliability of the controls that manage these risks. It is not just the number of controls that is crucial in managing risk – it is the strength of the controls that is essential to manage.

For more information on Bow-Tie diagrams see Wikipedia or search on the IChemE website:

Quantitative Risk Assessment (QRA)

A Quantitative Risk Assessment (QRA) is a very detailed analysis of a process plant to ensure that the risk to neighbouring sites, plants or residences meet planning guidelines. A common requirement is that the fatality risk at nearby residential properties must not exceed 1 in a million per year (1 x 10-6 p.a.)

A QRA is commonly considered the best approach for modern complex processing facilities handling hazardous materials. The standard industry methodologies for QRA are presented in the following publications:

  • ‘Guidelines for Chemical Process Quantitative Risk Analysis’, Centre for Chemical Process Safety, 2000
  • ‘Guideline for Quantitative Risk Assessment ‘Purple Book’ CPR 18E’, VROM, December 2005.

The Bow-Tie Consulting personnel have developed QRA’s for a large number of process plants. This experience will ensure that your site is modelled at an appropriate level of detail. This will reduce the cost associated with the model development while still providing detailed models of the significant risks. This understanding allows future risk reduction actions to be targeted in the most effective manner possible.

There are many parts of a QRA, such as hazard identification and consequence modelling. We will help you in any or all of these aspects. 

Major Hazard Facilities and Safety Case Development

The Major Hazard Facilities regulations now extend throughout Australia and require a Safety Case or Safety Report to be prepared that documents the safety management system on a MHF site. Our personnel work with our clients to assist them in the demonstration that their management systems are adequate to meet their requirements.
Bow-Tie Consulting will assist you in all of the steps to develop a safety case (also called a safety report) demonstrating the adequacy of the major accident risk controls and management systems.  This safety case/report will clearly demonstrate that:
  • You have identified all major accident hazards
  • You have effective controls are in place to manage the hazards
  • You have reduced the risk associated with each major accident hazard As Low As Reasonably Practicable (ALARP)
  • You have implemented robust management systems are in place to ensure that critical controls are maintained in good condition.
  • You have both leading and lagging measurements of the state of process safety in your plant.

Accident / Incident Investigation

We have experience in leading and participating in accident investigations, both within Australia and overseas. This has included the Royal Commission into the fatal accident that occurred at Longford in 1995 as well as other judicial inquiries (collision between two light aircraft causing fatalities; and spill of 70,000 L of sulfuric acid into a sensitive natural environment) and internal investigations.

Our experience allows us to plan and implement a timely and efficient accident investigation. We do this through using structured interviews as well as reviewing reports from experts, such as metallurgists and aviation engineers, to arrive at a reasoned understanding of what went wrong and how a similar accident could be prevented in the future.

Where necessary, we are able to present our findings in legal hearings, such as prosecution for polluting the environment, to aid the court in understanding technical aspects of the accident.

The investigation processes that Bow-Tie Consulting employs enable us to identify the relevant factors (and failures) that contributed to the incident.  The techniques used include:

  • Root Cause Analysis
  • Timeline analysis
  • Fault tree analysis
  • Event tree analysis

Hazard Identification

Bow-Tie Consulting’s personnel will work with you to ensure that this most critical phase of risk analysis is undertaken to an adequate level of detail. A risk that is not identified will not be managed and an in-depth hazard identification process may be required.

We often assist our clients in hazard identification as a prelude to undertaking hazard analysis and more detailed consideration of the risks. We use PHA-Pro software to record the results of the study because it manages the data effectively and produces reports in Microsoft Word format.

Hazards vary between operations, procedures used, materials present and organisations. Hazards may be any activity, procedure, plant, process, substance, situation or other circumstance that has the potential to cause harm.

Bow-Tie Consulting will use its experience in all the major hazard identification techniques to ensure that the technique used in your organisation will best suit your requirements, instead of following an inappropriate common procedure.

Where the site is more complex, a range of techniques may be required. The range of hazard identification techniques we may utilise in your organisation include:

  • HazId
  • FMEA
  • Task Analysis
  • Procedural HAZOP
  • Brainstorming
  • Fault-tree analysis
  • Operation accident history analysis

We will bring our extensive knowledge of hazard identification techniques to ensure the most appropriate are used for your situation.

Layers of Protection Analysis (LOPA)

Layer of Protection Analysis (LOPA) is used to assess the risk of major accidents by detailed consideration of the safeguards or controls that prevent or mitigate these accidents.  LOPA is a semi-quantitative method and fits between simplified qualitative techniques (such as a simple risk matrix) and complete quantitative assessment (QRA).  LOPA is often required where a higher degree of quantification of causes and controls is required due to the potential severity of the consequences. LOPA is also the preferred technique for SIL allocation studies due to the clear identification of independent layers of protection.


LOPA provides clear linkages between causes, controls and outcomes, analyses the effectiveness of individual controls and can demonstrate that the controls are adequate against simple risk criteria.
Bow-Tie Consulting’s personnel have experience in facilitating LOPA studies, whether alone or in conjunction with HAZOP studies or SIL allocation studies. Our Exida certified facilitator has undertaken numerous LOPA/SIL assessments and verification studies for clients in Australia and South Korea.


Qualitative / Semi-Quantitative Risk Assessment

A qualitative or semi-quantitative risk assessment can be used when there is not sufficient data to undertake a fully quantitative risk assessment (QRA) or when a QRA is not warranted.

The steps in a qualitative or semi-quantitative risk assessment should conform to the guidelines provided in AS/NZS ISO 31000:2009 "Risk Management - Principles and Guidelines"

In most qualitative or semi-quantitative risk assessments a risk matrix will be utilised, conforming to the guidelines provided in AS/NZS ISO 31000:2009 "Risk Management - Principles and Guidelines" . The advantage of using a risk matrix as the risk assessment tool is that it enables hazards to be quickly assessed to provide a comparison of risk levels between hazards.  This enables hazards that are not significant to be screened out and focuses management towards the more significant hazards.

Bow-Tie Consulting’s personnel have extensive experience in managing the workshop group to ensure that the chosen risk management controls are effective and that the controls will be adequate to manage the hazard.  This is one of the key skills that our facilitator brings to the risk workshop process.

A second skill to achieving the best outcomes from a workshop team is to ensure that there is involvement from all the stakeholders in the workshop. Our facilitator uses specific human interaction models to manage the human factors in workshops and is able to manage group participation to ensure the input from all people is captured and recorded.

If the information you require about our services and capabilities is not listed, please contact us and we will respond to your specific enquiry.