Have you ever wondered what residual risk means in the context of machine safety and what actions are necessary to manage it effectively? Can risk be completely eliminated, or must we learn to live with it and manage it effectively? This article will answer these questions: what exactly is residual risk, how to handle it, and at what level it can be considered acceptable.
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What is Residual Risk?
Residual risk refers to the level of threat that remains after implementing all possible protective measures and risk mitigation actions. Even the best-designed machines and safety systems cannot entirely eliminate all hazards—some risk will always remain, requiring management. In practice, this means that after conducting a risk analysis and implementing safety measures, situations may still exist that could lead to accidents. These situations are what we call residual risk.
The concept of residual risk is embedded in regulations related to machine safety, such as the Machinery Directive and standards like EN ISO 12100, which define the principles of designing safe machines. The Machinery Directive 2006/42/EC requires manufacturers to consider the machine’s work environment and the target user group, both professional and non-professional. Additionally, residual risk must be clearly communicated to the user through manuals, warnings, and pictograms to ensure that the operator is aware of all the hazards associated with machine use.
Managing Residual Risk — What to Do?
Is it possible to eliminate residual risk entirely? Unfortunately, complete elimination of risk is not feasible in most cases, but managing it is crucial for ensuring safety. What does this entail? Primarily, it involves clearly communicating to users what hazards may still be present during machine operation. The manufacturer or industrial automation integrator must provide appropriate documentation detailing all actions necessary to minimize risk associated with these hazards. This may include safe usage instructions, requirements for personal protective equipment, and the need for regular inspections and maintenance.
In managing residual risk, methods such as Risk Score and Preliminary Hazard Analysis (PHA) are beneficial. The Risk Score method quantifies risk by assigning numerical values to various risk aspects, facilitating the prioritization of corrective measures. PHA, used early in the machine design phase, helps integrate safety measures with machine functionality, proving more effective and cost-efficient than implementing changes post-project completion. Residual risk often remains even after a risk reduction plan is in place.
An example might be a machine guard covering gears—adding a warning pictogram helps prevent accidental removal of the guard during production line operation. Analysis allows for assessing, evaluating, and mitigating risk to an acceptable level.
Examples of managing residual risk include:
- Incorporating information about existing risks into user manuals so operators know how to minimize hazards.
- Training employees on residual risk management to ensure they are aware of potential hazards and know how to act if they occur.
- Marking machines with pictograms and warnings that clearly indicate possible hazards, such as when entering dangerous zones.
For instance, if a machine is equipped with a warning about risks when accessing a specific part, responsibility for further action lies not only with the designers but also with operators who must be aware of the hazards. Employee awareness and appropriate training in residual risk are crucial for reducing workplace accidents.
At What Level is Residual Risk Acceptable?
This raises the question: at what level can residual risk be considered acceptable? Acceptable risk levels are determined based on several factors, such as the severity of potential consequences, the likelihood of their occurrence, and the ability to avoid them. A risk matrix is often used, assessing risk scale based on two main parameters: likelihood of occurrence and severity of consequences.
For example, if the risk assessment scores 3 for likelihood (on a scale of 1-5) and 4 for severity (on a scale of 1-5), the resulting risk level is 12 (3 x 4). This result may be deemed acceptable or not, depending on the organization’s pre-established criteria.
However, it is crucial to remember that risk potentially causing permanent health damage should never be accepted. In such cases, further risk reduction is necessary, such as implementing additional protective measures.
Another important aspect is safeguarding against intentional operator actions that might bypass safety measures to expedite work. For instance, adding guards that block access to dangerous machine parts equipped with systems preventing easy removal during operation ensures that even intentional operator actions do not lead to situations threatening health or life.
Countermeasures and Residual Risk
Countermeasures to minimize residual risk include additional guards, restricted access to hazardous zones, and alarm systems. However, complete risk elimination is not always possible. Therefore, operators must be informed about actions to avoid undesirable events.
The TOL (Technical, Organizational, Human) principle is applied to eliminate risk. Initially, technical measures, such as inherently safe designs, are implemented. Then organizational measures follow, and finally, human measures, like personal protective equipment and training, are used.
Administrative measures, such as appropriate work procedures, training, and instructions, are also significant. These procedures are often based on risk analysis (e.g., FMEA), identifying potential hazards and assessing their likelihood. The analysis results are then used to develop safe machine operation guidelines.
Residual Risk Documentation
The Machinery Directive requires manufacturers to conduct proper risk assessments but does not specify a particular method. Risk analysis is necessary to ensure all significant hazards are identified and appropriate risk reduction measures are taken. It’s worth noting that the EN ISO 12100 standard harmonizes with the Machinery Directive, implying compliance with the Directive’s requirements, although it’s not the only method for conducting risk assessments.
FAQ: Residual Risk
Residual risk refers to the level of threat that remains after implementing all possible protective measures and risk mitigation actions. Despite safeguards, some level of threat may persist, requiring monitoring and appropriate management.
No, completely eliminating residual risk is usually not possible. In most cases, despite numerous protective measures, some risk remains. Therefore, managing residual risk and appropriately informing users of existing hazards is crucial.
To minimize residual risk, various measures can be employed, such as adding warnings and pictograms to machines, training employees on hazards, and implementing procedures to prevent accidental removal of safeguards. Regular machine inspections and maintenance are also essential.
Acceptable risk levels are determined based on several factors, such as the severity of potential consequences, the likelihood of their occurrence, and the ability to avoid them. A risk matrix is often used to assess risk scale. For example, risk that could cause permanent health damage cannot be considered acceptable and requires further protective measures.
Examples of managing residual risk include marking machines with pictograms warning of hazards, using guards to prevent access to dangerous machine parts, and training employees to be aware of potential hazards. It’s also important to consider possible intentional operator actions that might bypass safeguards, leading to dangerous situations