|
Category |
Requirements (in
brief)
|
System Behavior
|
Principle
|
|
B |
Safety related parts
of control systems and/or their safety devices and
their components must be designed, constructed,
selected, assembled and combined in accordance with
the relevant standards such that they can withstand
the expected influence.
|
The occurrence of a
fault can lead to loss of the safety function.
|
mainly characterized
by the selection of components
|
|
1 |
The requirements of B
shall apply. Well-tried components and
well-tried safety principles shall be used.
|
The occurrence of a
fault can lead to loss of the safety function., but
the probability of occurrence is lower that in
category B.
|
|
2 |
The requirements of B
and well-tried safety principles shall apply.
The safety function
shall be checked at suitable intervals by the
machinery control system.
|
The occurrence of a
fault can lead to loss of the safety function
between the checks. The loss of the safety
function is detected by the check.
|
mainly characterized
by the structure
|
|
3 |
The requirements of B
and well-tried safety principles shall apply.
-
a single fault
in any of these parts does not lead to the loss
of safety function, and
-
the single fault
is detected whenever reasonably practicable.
|
If the single fault
occurs, the safety function is still maintained.
Some, but not all
faults are detected.
Accumulation of
undetected faults can lead to loss of safety
function.
|
|
4 |
The requirements of B
and well-tried safety principles shall apply.
-
a single fault
in any of these parts does not lead to the loss
of safety function, and
-
the single fault
is detected during or prior to the next demand
on the safety function, or, if this is not
possible, the accumulation of faults should not
as a result lead to the loss of safety function.
|
If faults occur, the
safety function is still maintained. Faults
are detected in good time to prevent the loss of
safety function.
|
Unidrive
