Keba KeTop T100, User Manual, Page: 136 / 163

The category of the Performance Level determines if
●
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)
●
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. 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. The PL must always be con-
sidered 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.
14.2.7 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
that the operator can overlook the operating area.
The handheld terminal has the advantage that the operator can get very close
to the control panel.
CE Conformity, Directives and Standards KeTop T50VGA
© KEBA 2009
User's Manual V1.50 136