03 49006 risk tolerability alarp v02(1)
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Faculty of Engineering and Information Technology University of Technology, Sydney
Risk Management 49006
Risk tolerability
A/Prof David Eager [email protected] www.eng.uts.edu.au/~deager
Faculty of Engineering and Information Technology University of Technology, Sydney
Tolerability does not mean acceptability It refers to a willingness to live with a risk so as to
secure certain benefits and in the confidence that it is being properly controlled
To tolerate a risk means that we do not regard it as negligible or something we might ignore, but rather as something we need to keep under review and reduce still further if and as we can
For a risk to be acceptable on the other hand means that for purposes of life or work, we are prepared to take it pretty well as it is
Risk Tolerability - ALARP
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Faculty of Engineering and Information Technology University of Technology, Sydney
Whenever we do something that involves taking a risk - even stepping off a footpath when there may be traffic - we usually do so because we believe there is some benefit that outweighs the risk
We are likely to take the consequence for granted, to estimate the risk, however instinctively, and then see if we can reduce or avoid it
These simple principles apply to all risks
Risk Tolerability - ALARP
Faculty of Engineering and Information Technology University of Technology, Sydney
All products, services and systems include hazards, and some residual risk
The risk associated with those hazards should be reduced to a tolerable level
Tolerable risk is determined by the search for an optimal balance between the ideal of absolute safety and the demands to be met by a product, service or system, and the factors such as benefits to the user, suitability for the purpose, cost effectiveness, and conventions of society concerned
Note: The concept of reducing risk to a tolerable level varies significantly depending on whether the product or system is used in the workplace, in the public environment, or by a consumer in the home
Risk Tolerability - ALARP
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Faculty of Engineering and Information Technology University of Technology, Sydney
After the risk reduction measures have been implemented, their effectiveness should be validated to ensure they are effective
The outcome of a risk assessment should be documented
The document should demonstrate the procedure that has been followed, the hazards identified and the risk reduction measures employed to reduce risk to an acceptable level
Risk Tolerability - ALARP
Faculty of Engineering and Information Technology University of Technology, Sydney
When considering safety aspects for products, processes and services, the foreseeable uses and potential misuses of the product shall be considered
Foreseeable use takes into consideration the developmental stage of the intended user since different age groups interact differently with products based on their behavioural, skill and physical capabilities
To many suppliers this may manifest itself as the user is not using the product for its intended purpose rather than normal expected behaviour that needs to be considered when designing a product
Risk Tolerability - ALARP
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Faculty of Engineering and Information Technology University of Technology, Sydney
All product suppliers shall consider safety aspects for the intended uses and the reasonably foreseeable misuses of the product, and to apply risk reduction measures to achieve a tolerable risk level
Product suppliers should also consider reasonably foreseeable uses of the product which although may not be intended uses are readily predictable based on the user population
In particular, when determining the risk posed by a consumer product, special consideration should be given for products that are intended for, or are used by, children and vulnerable consumers who are often unable to understand the risks involved
Risk Tolerability - ALARP
Faculty of Engineering and Information Technology University of Technology, Sydney
The minimum necessary risk reduction is the reduction in risk that has to be achieved to meet the tolerable risk (acceptable risk) for a specific situation
The concept of necessary risk reduction is of fundamental importance in the development of the safety requirements for products and systems
The purpose of determining the tolerable risk (acceptable risk) for a specific hazardous event is to state what is deemed reasonable with respect to both components of risk
Risk Tolerability - ALARP
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Faculty of Engineering and Information Technology University of Technology, Sydney
Risk Reduction Phases
Faculty of Engineering and Information Technology University of Technology, Sydney
The tolerable risk (acceptable risk) will depend on many factors: for example, severity of injury, the damage to property or the environment, the frequency at which a person or people are exposed to danger and the duration of the exposure, and the practicability of the technical means to reduce the risk
When several risks have to be dealt at the same time, caution shall be taken to ensure that the risk reduction measures chosen for one risk has not increased or introduced another risk
Risk Tolerability - ALARP
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Faculty of Engineering and Information Technology University of Technology, Sydney
If there is more than one option for risk reduction the Engineer should endeavour to clearly show the client the principles of implementing a risk assessment so that they can conduct a thorough investigation to determine the most appropriate method of reducing risk to a tolerable level
In such cases suppliers have increased responsibility for the safety of their products and systems
It may also be appropriate for the supplier to determine the most appropriate risk reduction measure if the equipment in question is particularly complex as they will have the best knowledge of its specific characteristics and components
Risk Tolerability - ALARP
Faculty of Engineering and Information Technology University of Technology, Sydney
Besides the risks each of us willingly takes to secure benefits we want, we also face a degree of risk from naturally occurring hazards
There is, for example, a chance of one in 10 million each year that any one of us will be killed by lightning
Because lightning generally kills only one person at a time, and the risk to each of us is very low, we treat it as negligible (ie apart from taking certain simple precautions the possibility of dying in this way does not influence our behaviour)
Risk Tolerability - ALARP
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Faculty of Engineering and Information Technology University of Technology, Sydney
Risk Tolerability - ALARP
Faculty of Engineering and Information Technology University of Technology, Sydney
Risk Tolerability - ALARP
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Faculty of Engineering and Information Technology University of Technology, Sydney
Risk Tolerability - ALARP
Faculty of Engineering and Information Technology University of Technology, Sydney
Risk Tolerability - ALARP
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Faculty of Engineering and Information Technology University of Technology, Sydney
We also know 3 other important things about risk: There is no such thing as nil risk (no matter what
we are doing) No matter how remote a risk, it could just turn up
(remote risk is not the same as no risk at all) That our own chances may be either more or less
than the average, depending on where we live, whether we are more nimble, or younger, or have better sight, and so on
Risk Tolerability - ALARP
Faculty of Engineering and Information Technology University of Technology, Sydney
Individuals are prepared to tolerate some risks under certain circumstances in return for specified benefits
The simplest risk criteria divides risks that need treatment from those which do not
This gives attractively simple results but does not reflect uncertainties either in estimating risks or in defining the boundary between those that require treatment and those that do not
Risk Tolerability - ALARP
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Faculty of Engineering and Information Technology University of Technology, Sydney
A common approach is to divide risks into three bands: (a) An upper band where adverse risks are intolerable whatever benefits the activity may bring, and risk reduction measures are essential whatever their cost (b) A middle band (or grey area) where costs and benefits are taken into account and opportunities balanced against potential adverse consequences (c) A lower band where positive or negative risks are negligible or so small that no risk treatment measures are needed
Risk Tolerability - ALARP
Faculty of Engineering and Information Technology University of Technology, Sydney
The ALARP Principle ‘carrot diagram’
Risk Tolerability - ALARP
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Faculty of Engineering and Information Technology University of Technology, Sydney
ALARP – Quantification values
Risk Tolerability - ALARP
Faculty of Engineering and Information Technology University of Technology, Sydney
For risks with significant potential work, health, safety or environmental consequences, this is expressed as the As Low As Reasonably Practicable or ALARP concept (it is also applicable for other risks)
The width of the cone indicates the size of risk and the cone is divided into bands
When risk is close to the intolerable level the expectation is that risk will be reduced unless the cost of reducing the risk is grossly disproportionate to the benefits gained
Risk Tolerability - ALARP
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Faculty of Engineering and Information Technology University of Technology, Sydney
Where risks are close to the negligible level then action may only be taken to reduce risk where benefits exceed the costs of reduction
The concept of practicability in ALARP contains within it the ideas of practicality (ie can something be done) as well as the costs and benefits of action or inaction (ie is it worth doing something in the circumstances)
These two aspects need to be balanced carefully if the risks the organization is treating are related to an expressed or implied duty of care or the reasonably practicable test
Risk Tolerability - ALARP
Faculty of Engineering and Information Technology University of Technology, Sydney
Lord Justice Asquith as far as 1949 provided the now famous definition for reasonably practicable: ‘Reasonably practicable’ is a narrower term than ‘physically possible’ and it seems to me to imply that a computation must be made by the owner, in which the quantum of risk is placed on one scale and the sacrifice involved in the measures necessary for averting the risk (whether in money, time or trouble) is placed in the other; and that if it be shown that there is a gross disproportion between them — the risk being insignificant in relation to the sacrifice — the defendants discharge the onus on them
Risk Tolerability - ALARP
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Faculty of Engineering and Information Technology University of Technology, Sydney
ALARP principle is ’the point where the incremental risk reduction achieved by additional Risk Management resources is outweighed by the cost of these resources’
The essence is that there is a demonstration that risks have been reduced ALARP is to show that the ‘cost’ of improving safety further would be grossly disproportionate to the benefits that would accrue from implementing any further options for improvement or change to the status quo
This does not mean that a detailed analysis is necessary: the emphasis must be on an analysis which is fit for purpose
Risk Tolerability - ALARP
Faculty of Engineering and Information Technology University of Technology, Sydney
The following principles should be addressed (in most cases): The application of ALARP can only be to risks which
you control Affordability ie the cost of implementing the
improvement ALARP demonstrations ought to consider the
various options which could improve the level of safety, and implement the option or combination of options which achieves the lowest level of residual risk provided this is reasonably practicable
The timescale for implementation may be a factor in the choice of options
Risk Tolerability - ALARP
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Faculty of Engineering and Information Technology University of Technology, Sydney
(cont.) Options may include partial implementation or
implementation of more than one measure as appropriate (not valid to argue that a solution requires only a whole or single measure)
You will need to demonstrate the consequences of accidents (the detriments), in terms of deaths/injuries, food bans etc, so that you can justify/compare these with the sacrifice entailed with the implementation of any measures
The ALARP case should be fit for purpose
Risk Tolerability - ALARP
Faculty of Engineering and Information Technology University of Technology, Sydney
(cont.) If the risks are high then a demonstration of ALARP
would need to be more rigorous than if the risks are low
The degree of rigour should also depend on the consequence level
For higher consequence situations the consequences should weigh more heavily than the frequency estimates
Furthermore thought should be given to the robustness of the conclusions with respect to uncertainties and to any assumptions employed in the demonstration
Risk Tolerability - ALARP
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Faculty of Engineering and Information Technology University of Technology, Sydney
How effective is your ALARP, ask these questions: Where are you pitching your controls – Elimination… or
PPE? How good are the controls you have in place? Are the controls actually available? Are the controls reliable, resilient and effective? Does the control actually address the hazard? Will the controls be used? Will the control ‘survive’ the initial accident or incident? Does the control rely on the intervention of a person eg
the operator, or are they automatic? Do your controls meet legislative requirements?
Risk Tolerability - ALARP
Faculty of Engineering and Information Technology University of Technology, Sydney
Risk tolerability
A/Prof David Eager [email protected] www.eng.uts.edu.au/~deager
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