• Bowties diagrams and human factors

    Bowtie diagrams were developed in the 1970s as a way of illustrating how risks are managed. Their use increased significantly after the Piper Alpha disaster and continues to this day. Although originating in the process industry, other sectors are starting to use Bowtie diagrams.

    However, the popularity of Bowtie diagrams is not without its problems. There has been no definitive guide or standard on how to develop them, or even when they should be used. People clearly like Bowtie diagrams, but often have inflated opinions of what they can actually achieve and there is a misguided assumption that they can be applied to any activity where there is risk. Representation of human factors is one particular area where there appears to be a lot of variability and differences of opinion. 

    I have written this paper to share my views of how Bowtie diagrams should be used and how human factors should be represented. I hoped it would start some discussion. If you have any comments, I would be very happy to receive them.

    Bowtie diagrams and human factors (full paper in PDF format)

  • Interlocking isolation valves - less is more

    Interlocks provide a means of coordinating the function of different components so that task steps have to be performed in a specified sequence or certain conditions have to be met before a task can proceed. Valves used to create process isolations can be interlocked so that it is physically impossible to manoeuvre them in an incorrect sequence. This is often seen as a method of eliminating the potential for human error.

    Advances in technology have allowed more extensive and complex interlocks to be used, which on the face of it, appears to provide the opportunity to make isolations safer than ever before. However, interlocks do not actually eliminate errors; and complexity can be a source of risk. In fact, when all factors are considered there may be an argument to say ‘less is more.’

    Whilst there is some guidance available about when interlocks can or should be used; there is very little to say which or how many components should be interlocked. This leaves designers with a dilemma. Do they attempt to apply a ‘sensible’ approach, which may leave them open to criticism because their design is not totally ‘error proof?’ Or do they go to an interlock vendor and ask them to interlock everything,?

    One of the problems is that the reason for using interlocks is not always clearly understood or defined. Are they provided to:
    • Ensure a ‘spared’ item (e.g. relief valve, filter) remains available at all times and is not interrupted when changing over duty/standby?
    • Ensure isolation valves are in the correct position before carrying out a task?
    • Ensure the item has been fully isolated and prepared for the task by ensuring valves are manoeuvred in a defined sequence and secured in the correct position;
    • All of the above?

    Extensive and complex interlock systems are expensive to purchase, install and maintain. They are often only effective for performing one task, and so cause significant problems when other activities have to be performed or if a problem occurs (e.g. valve passes or pipework is blocked). Also, they can create a false sense of security that introduces human factors risks. This paper will discuss these issues using real life examples and suggest that less really can be more.


    Presented at Hazards 2017

  • Human factors Engineering (HFE) early in projects

    Whilst Human Factors Engineering (HFE) is starting to be adopted for projects in the oil and gas industry, there is a tendency to leave it until relatively late. This means that opportunities to influence and improve the design are being missed. The reasons for this include a lack of understanding of what HFE can contribute amongst project personnel; and a similar lack of project understanding by the people responsible for integrating human factors. This paper will make the case of doing more HFE earlier in projects, which will improve the way human factors are addressed and result in better design.

    Presented at EHF 2017

  • Emergency Procedures

    Effective emergency procedures that support the people who have to detect, diagnose and respond to hazardous situations can reduce the likelihood that minor incidents will escalate.  Unfortunately, procedures often fail to support the people who have to deal with the early stages of an incident. This paper examines the reasons why emergency procedures may not provide adequate support, and sets out some guidelines to help in writing more effective ones.

    Published in the Loss Prevention Bulletin April 2017

  • Double block and bleed - it's more complicated than you think

    The double block and bleed method of valve isolation has become almost the default method of isolation in the process industry. However, there are limitations and misunderstandings in the methods of proving integrity.  This paper highlights several ways in which double block and bleed isolations can fail, resulting in hazards with major accident potential. Key learning points include:

    • Implementing an isolation involves more than simply closing some valves;
    • Multiple failures can and do occur — and because valves are often of the same type and in the same service, common cause failures are an issue;
    • Valve integrity must be proven and this requires pressure. There will be times when no pressure is available from the process, or it is only available from the wrong direction;
    • Reducing the risk to personnel carrying out maintenance will often be transferred to those implementing the isolation.


    Published in the Loss Prevention Bulletin August 2016

  • Integrating Human Factors into Major Accident Safety Studies

    This paper is a development of one I presented at Hazards 24 [Ref 1]. I believe that human factors can make a great contribution to the way the risks of major accidents are managed. However, whilst its use in industry is growing it is failing to reach its potential because it is not properly integrated into other safety studies.  Task analysis is arguably the human factors technique that has the greatest potential for overcoming this hurdle.

    Linking Human Factors to Safety Studies (download full paper in PDF format)

  • Ten Years of Staffing Assessments

    In 2001 a document Contract Research Report (CRR) 348/2001 was published by the Health and Safety Executive (HSE) that introduced a method of assessing staffing arrangements for process operations in the chemical and allied industries.  I’ve lost count, but over the last 10 years I have been involved in at least 30 staffing assessment projects for more than 15 different clients.  Also, even where the method is not formally used I often refer to elements of it as guidance for my other human factors and risk consultancy work.  Having spent 10 years using the method I decided it was a good time to stand back and reflect.  In general, although I can point to some flaws in the method, I have found it to be a very good framework for assessing human and organisational factors.  It prompts you to ask challenging questions and to be objective in your analysis.  Also, I have found that the observations and recommendations I have made as a result of using the method have been very well received by my clients.

    Download my Christmas 2011 Paper - 10 Years of Staffing Assessments

  • Human Factors

    All organisations involve people in some way.  One issue that this brings is that all people make mistakes, forget things, get distracted, break rules and generally fail.  Human Factors helps us understand how people fail, the potential consequences of failure and how the associated risks can be reduced.

  • Task Risk Management

    This paper proposes Task Risk Management as a means of integrating the principles of task analysis into a wider risk management process. The paper describes methods and approaches that I have used and found to be very effective and practical.

    I have used the term Task Risk Management to show the benefits of taking a task based approach prioritised around process safety risks. I believe that done properly, the way human factors and process risks are understood and managed can be improved significantly.

    Task Risk Management (full paper in PDF format)

    Task Risk Management job aid

  • Improving shift handover and maximising its value to the business

    Recent accidents at Buncefield and Texas City have illustrated how poor shift handover can contribute to major accidents.  This is not a new discovery, but given the ever greater interest in human factors, it is one that is finally receiving attention.

    Shift handover is a complex, high risk activity that is performed very frequently.  Normally we would try to ‘engineer out’ high risk frequent tasks, or at least automate them to minimise the likelihood of error.  However, this is not an option for shift handover.

    Co-author Brian Pacitti of Infotechnics

    Shift handover paper (PDF format)

  • A control room is only a component in a complex system

    The design of modern control rooms has benefited a great deal from ergonomics and resulted in working environment, furniture and human-machine interfaces that are more consistent with the needs of the people who work in them.  However, I feel that many people involved in the design of control rooms assume that using the latest technology and following the most up to date standards will result in a successful outcome.  They are reassured that what they have developed looks like a control should, but fail to understand that they are not simple objects that can be defined by their physical arrangements.  A control room is actually a component of a complex system where people and equipment come together to control that system.

    Control room human factors paper (PDF format)

  • Moving from training to competence systems

    Companies have invested a great deal of time and effort into training over the years, and it is not the intention here to say that this has all been wasted.  However, unless training is closely linked to a competence system the chance are that the fundamental requirements of the business may not be met because the training provided may not be what is required and/or the cost of that training may be greater than the benefit achieved.

    Moving from training to competence (PDF format)

  • Staffing & teamwork


    Tug of war


    There are a lot of issues that relate to staffing levels and how individuals work as teams.  However, it can be difficult to discuss them as abstract ideas.

    Using an analogy based on 'tug of war,' a number of staffing and teamwork scenarios are discussed. Can bigger teams always achieve more than smaller ones?  Does everyone have to be hands on?  How do technical and engineering solutions fit in?

    Download a PDF version

  • Procedures

    I think everyone is familiar with procedures, but do we really know what they are?  Dictionary definitions vary, but they typically suggest a procedure is:

    • A manner of proceeding; a way of performing or effecting something.
    • A series of steps taken to accomplish an end.
    • A set of established forms or methods for conducting the affairs of an organised body such as a business, club, or government.

    Interestingly none of the definitions refer to written documents. However, in practice it is generally accepted that a procedure is written in a way that describes a task method.

  • Risk Management

    Although people often want to eliminate risk, this is simply not possible.  Instead it is important we understand the risk we undertake, put sensible controls in place and then make a conscious decision about whether we are happy to accept the risks that remain.  This is what we call risk management.

  • Safety Procedures that Work


    Special Report for Indicator Tips & Advice - Health & Safety

    Available to purchase here

  • Accident Avoidance


    Special Report for Indicator Tips & Advice - Health & Safety

    Available to purchase here

  • Safe staffing arrangements - applying the user guide


    Presented at seminar titled 'Workload, organisational change and stress'

    Energy Institute, London

  • Safe staffing arrangements - user guide for CRR348/2001 methodology


    Guidance Document -available here

    Energy Institute

    Co-authors P Waite and A Gait

  • Different Types of supervision and the Impact on Safety in the Chemical and Allied Industries


    Health and Safety Executive Research Report RR292

    Co-authors A Gait and P Waite