Are the safety functions of your machine adequately equipped?
Are the selected components suitable? And are these components used correctly?
To answer these questions, we must use the standard ISO 13849:
Step 1: Determining the necessary performance level
The severity of the injury, the frequency and/or duration of exposure to the hazard, as well as the possibility of avoiding the hazard are all taken into account.
Severity of injury:
S1: minor (usually reversible) injury
S2: major (usually irreversible) injury including death
Frequency and/or duration of exposure to the hazard:
F1: rare to less often and/or the time of exposure to the hazard is short
F2: often to constant and/or the time of exposure to the hazard is long
Possibility of avoiding the hazard or limiting the damage:
P1: possible under certain conditions
P2: hardly possible
Step 2: Determining the components to be used to achieve the necessary performance level
Depending on the performance level to be achieved, one of the following architectures is selected:
Single-channel. One single error can lead to failure of the safety function.
Single-channel using proven components and proven safety principles. One single error can lead to failure of the safety function, however the probability is lower than with category B.
Use of proven safety principles incl. regular monitoring of the safety function.
Two-channel. When one single error occurs, the safety function can continue to run. Not all errors are recognised.
Two-channel. When one single error occurs, the safety function can continue to run. All possible errors are recognised.
The following values must be calculated to determine the achieved performance level:
MTTFd: Time until dangerous failure
DCavg: Diagnostic coverage
The technical data of the individual components and the selected architecture are necessary for these calculations.
Step 3: Documentation
The conditions of the necessary and achieved performance level must be documented. The easiest way to do this is to use a corresponding tool.
We are happy to support you in the development and documentation of your safety function.
Thomas Fäh, CMSE® Certified Machinery Safety Expert