Keba Kemro KeTop T10, Руководство по проектированию устройства

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The category of the Performance Level determines if
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the system has been built in single circuit technology, which means that a
failure will lead to a loss of safety, although the availability of components
and parts is high (category 1)
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the system has been built in single circuit technology, which means that a
failure will lead to a loss of safety, but the failure will be detected by the
system and will be displayed somehow or other (category 2)
●
the system has been built in multiple (2) circuit technology and that a fault
will not lead to loss of safety (category 3) or
●
the system has been built in multiple (2) circuit technology and a build up
of multiple faults will not lead to loss of safety (category 4).
Starting from category 3 it is also important in this context that individual faults
are detected in time to avoid a build up of faults, which may finally lead to loss
of safety.
Faults that have to be detected in electric and electronic systems are for ex-
ample short circuits between multiple circuits, interrupts, short circuits or
contacts that are stuck together. Special certified safety control devices are
often used to detect faults in the individual safety circuits, which have a certain
PL. The PL quoted for these devices is only attained, however, if also the whole
machine circuit under review lies within the scope of the respective PL and the
PL of all components supporting the safety functions has to be considered.
The PL must always be considered in relation to a complete safety function
and not as applied to individual components or parts.
A guide for easily calculating the PL for a safety function consisting of several
individual components can be found in standard EN ISO 13849-1 chapter 6.3
and appendix H and I.
If safety components are being connected in series, the individual component
with the least PL determines the PL of the whole safety function. For example
a safety function consisting of 3 components, one with category 4 PL e, another
one with category 3 PL d and a third component with category 2 PL c will have
a PL c for the whole safety function. This means that a fault will lead to loss of
safety, although components with category 4 PL e are integrated into the safety
function, as one of the components being used has category 2.
When chaining several PLs the overall PL can decrease. For more information
read EN 13849-1 chapter 6.3.
The proof of attainment of a safety category can take place with the aid of an
FMEA (Failure Mode and Effects Analysis), in which all the faults that could
possibly arise are simulated, either theoretically or in practice, and it is dem-
onstrated that the requirements of the category are fulfilled.
17.7 Application of Handheld Terminals in Special Operating Modes
For the manual control of machines in special operating modes, where safety
depends on the timely reaction of the operating staff, it is absolutely essential
KeTop T10 Appendix: Machinery Safety
© KEBA 2014
Project engineering manual V1.02 65