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To make a machine functionally safe, machine builders must comply with a number of different standards and directives. To then market the machine within the European Economic Area requires CE marking, which represents legally binding confirmation by the manufacturer that all standards and directives relevant to the safety of the machine have been complied with. This blog explains the purpose of the risk assessment required in this context, and how to ensure the functional safety of the machine in accordance with the regulations.
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The basic standard EN ISO 12100 plays a central role in machine safety. The previously relevant standards EN ISO 12100-1:2003, EN ISO 12100-2:2003 and EN ISO 14121-1:2007 were combined into EN ISO 12100 back in 2010. This standard defines basic safety requirements and outlines numerous processes, including a detailed risk assessment procedure. The aim of this risk assessment is to reduce risks as far as possible, identify any hazards that may arise from the machine, take appropriate safety measures, and inform machine operators of any remaining residual risks. A machine cannot obtain CE marking if a risk assessment has not been conducted.
Special note: The term "risk analysis" has been replaced by the term "risk assessment" in both DIN EN ISO 12100:2010 and the Machinery Directive 2006/42/EC.
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Depending on the application, machine builders have to consider other standards and guidelines in addition to EN ISO 12100. More details can be found in our functional safety blog. Part 2 of DIN ISO/TR 14121 "Safety of machinery—risk assessment" is worth highlighting in this regard. It uses examples to demonstrate some of the methods and tools for completing the individual steps of a risk assessment. It also contains a guide to conducting risk assessments on machines, including example processes, which complies with the requirements of EN ISO 12100.
Machine designers should ideally start assessing risk right from the planning stage of their project, i.e. before design, according to the following steps:
Define the limits and intended use of the machine.
Identify potential hazards and hazardous situations.
Estimate the risks for each hazard or hazardous situation.
Evaluate the risks and make informed decisions on the need to reduce risk.
If the risk assessment indicates that risk reduction is required, appropriate safety measures must be taken in three stages using the following method:
The priority is to choose an inherently safe design using suitable design features.
Then, i.e. if an inherently safe design is not feasible, suitable technical safety features must be implemented (e.g. emergency shutdown, safety relay technology for monitoring movable guards or safe operation via a two-hand control). The Eaton safety manual provides detailed information about this, as well as useful wiring and calculation examples.
If any hazards cannot be adequately eliminated in the first two steps, the machine operator must be informed about the residual risks with clear warnings in the operating instructions or with warning symbols at the point of risk.
The four risk assessment steps mentioned above will now be explained in more detail.
The first step is to define the limits of the machine's use for all stages of its service life. The term "limits of use" covers both operating limits and spatial/temporal limits. The limits of use cover areas such as the intended use, foreseeable malfunctions and misuse, operating modes and areas of application. Consideration must also be given to who will operate the machine and who will not, and what qualifications and experience personnel need to operate and maintain the machine. Spatial limits include the temperatures at which the machine will be used, whether it will be used outdoors, and how safe distances and space requirements for operators can be implemented. The time limits concern factors such as maintenance intervals and the durability of wearing parts.
The hazard analysis is a complicated part of the risk assessment because it necessitates identifying all relevant hazards, be they electrical, mechanical, chemical or physical. It is therefore advisable to use the tables in Annex B of EN ISO 12100 as checklists when identifying the hazards. It is also necessary to assess the machine’s environmental and operating conditions. It may be helpful to know what events (such as material feed, maintenance, component failure or incorrect operation) may cause harm.
Steps 1 and 2 together are also referred to as risk analysis.
In the third step, two risk elements must be defined for each hazardous situation:
Extent of harm depending on severity from 1 (minor, reversible) to 4 (catastrophic, irreversible)
Probability of harm occurring, taking into account:
Risk matrix as a graphic overview for risk assessment
(Image source: ISO TR 14121-2 / WEKA business portal, risk assessment for machines, author: Jürgen Bialek)
In order to assess whether risk reduction measures are required, the designer must now evaluate the risk. This must be done in accordance with EN ISO 12100 following the three stages listed above. The risk assessment must then be repeated until all possible hazards have been addressed appropriately.
The documentation of the risk assessment and the safety measures installed provide proof that all significant hazards have been identified and appropriate precautions have been taken.
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