Appendix
5.3.3.3
Requirements on the control categories
Short description of the requirements on the individual categories according to EN 954-1
(Full version of the requirements: EN 954-1 paragraph 6)
Category
1
)
(EN954-1, ...)
Requirements
System reaction
2
)
Principles to ensure
safety
B
(6.2.1)
All safety-related parts and components of controls and/or their
protective devices must be designed, built, selected, assembled and
combined in accordance with the relevant standards to ensure that
they can resist to the influences to be expected.
The occurrence of an error can lead to the
loss of the safety function.
Mainly characterised by the
selection of components.
1
(6.2.2)
•
The requirements of “B” must be fulfilled.
•
Proven components have to be used.
•
The official safety regulations have to be observed.
The occurrence of an error can lead to the
loss of a safety function, it is, however, less
likely that an error will occur than in
category B.
2
(6.2.3)
•
The requirements of “B” must be fulfilled.
•
The official safety regulations have to be observed.
•
The safety function must be checked at appropriate intervals by
the machine control.
•
The occurrence of an error can lead to
the loss of the safety function between
the test intervals.
•
The loss of the safety function is
recognised by the test function.
3
(6.2.4)
•
The requirements of “B” must be fulfilled.
•
The official safety regulations have to be observed.
•
Safety-related parts must be designed as follows:
– in none of the parts, a single error may lead to the loss of the
safety function,
– the individual errors are recognised and removed accordingly
(not time-critical).
•
The safety function is always maintained,
if the individual error occurs.
•
Some, but not all errors are recognised.
•
The accumulation of unrecognised errors
can lead to the loss of the safety
function.
Mainly characterised by the
structure.
4
(6.2.5)
•
The requirements of “B” must be fulfilled.
•
The official safety regulations have to be observed.
•
The safety-related parts must be designed as follows:
– in none of the parts, a single error may lead to the loss of the
safety function,
– the individual errors must be recognised before or during the
next application of the safety function. If this is not possible,
the accumulation of errors must not lead to the loss of the
safety function.
•
The safety function is always maintained
when errors occur.
•
Errors are recognised in time to prevent
the loss of the safety function.
1) The categories have not been defined in the intention to be applied in a specified order or in a hierarchical order with regard to safety
requirements.
2) The risk assessment shows, whether the entire or partial loss of the safety function(s) due to errors can be accepted.
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