Nachi RMU20-20, Instruction Manual

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1.2 Risk Assessment
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1.2 Risk Assessment
Risk assessment involves ascertaining the sources of danger latent in a machine, assessing the extent of
those dangers (risks) and reducing the risk until the system is deemed to be safe.
Proceed with the risk assessment in accordance with the IEC 61508 standard.
The procedure involved is as follows:
1) Analyze the robot and its peripheral equipment, assess the entire system including its operating modes,
identify the sources of danger, and estimate the risk of those dangers.
2) Assess the risks using SIL (safety integrity level) as per the IEC 61508 standard.
3) Take action to reduce the risks if the results of the risk assessment suggest that the system is not safe.
4) Keep repeating the above steps until the entire robot system is judged to be safe.
This procedure is stipulated in the ISO 12100 and ISO 14121 standards.
Safety integrity level (SIL)
SIL is stipulated in the IEC 61508 standard.
In this method of assessing risks, consideration is given to the extent of the effects of the danger events, the
frequency of the exposure to them, the possibility of avoiding them and their probability with which they occur,
and the frequency of parts failures is categorized into the four levels of 1 to 4. The target failure frequency is
established in accordance with each of these SIL levels, and if a system does not reach the frequency of that
level, it is deemed to be not safe.
In continuous operation mode (high-demand operation mode of the IEC 61508), RMU20 is has been designed
to conform to SIL3.
For further details, refer to the IEC 61508 standard.
Action for reducing risks
If, as a result of risk assessment, the robot and its peripheral equipment are deemed to be not safe, the risks
must be reduced. Measures to take for reducing risks are stipulated in the ISO 12100 and ISO 14121 standards
so implement one or more risk reduction measures until the robot and its peripheral equipment are made safe.