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Rockwell Automation Publication IASIMP-QS005H-EN-P - April 2016
Chapter 1
Risk Assessment and System Design
Conducting a Team-based Risk Assessment
A formal team-based risk assessment is a task-by-task evaluation of the hazards that operators, technicians, and other
personnel may come in contact with. The results of a risk assessment help designers identify a more complete list of
hazards that can be addressed and mitigated by following a formal process.
The formal process embraces a hierarchy of measures for risk reduction that includes system redesign, engineered
guarding, administrative and training requirements, awareness means, and personal protective equipment (PPE)
identification. This leads to a systematic approach to reducing risk, not a guarding bandage approach.
Risk assessments include a risk rating system for identifying the risk level for each task and hazard combination. Once the
hazards are understood, mitigation techniques are applied to lower the risk to an acceptable level. A system designer who
uses a formal risk assessment methodology, based on safety standards, shows due diligence in the safety system design.
Some formal processes and standards also provide steps to identify the residual risk after the mitigation techniques have
been applied and provide guidelines on what is an acceptable level of residual risk.
Overall, the risk assessment process establishes the appropriate level of safety guarding, so that you don’t over- or under-
design but apply the right level of risk mitigation to the hazard.
Task and Hazard Identification
All of the hazards at the machine must be identified and listed in terms of their nature and location. Examples of hazards
include crushing, shearing, entanglement, part ejections, fumes, radiation, heat, noise, and more.
For each hazard, be sure to identify the energy source and component that could cause the injury, such as a crushed arm
due to powered robot motion or a crushed hand due to uncontrolled vertical motion from the potential energy of a
gantry.
The results of a task analysis should be compared with the results of hazard identification to show where there are
possibilities for the convergence of a hazard and a hazardous situation.
Risk Estimation
Any machine that has the potential for hazardous situations presents a risk of a hazardous event, that is, causing physical
harm, property or environmental damage. The greater the risk, the more important it becomes to do something about it.
To make a decision on how to respond to the risk, you need to be able to quantify it.
Risk is often thought of solely in terms of the severity of injury at an accident. Both the severity of potential harm and the
probability of its occurrence have to be taken into account to estimate the amount of risk present. Probability of
occurrence comprises two factors: the frequency of exposure and the possibility of avoidance. Risk estimation assigns
values to each of these factors, which are then used to determine appropriate risk reduction measures that are feasible,
realistic, and cost-effective.
ISO 13849-1 provides methods and guidance on how to specify a safety-related control system that is providing a
protective measure or safety function.