4. Functional safety engineering
80 Festo.P.BE-CMMS-ST-G2-HW-EN 1008NH
F1 Seldom to less often and/or the time of the exposure to hazard is short
F2 Frequent to continuous and/or the time of the exposure to hazard is long
P Possibility to avoid the hazard or limit the damage
P1 Possible under certain conditions
P2 Scarcely possible
Fig. 4.1 Risk graph for definition of the PL
r
Among other issues, the EN 60204-1 standard deals with the handling of emergencies and
defines the terms EMERGENCY OFF and EMERGENCY STOP (see table).
Handling Definition (EN 60204-1) Danger case
EMERGENCY
OFF
Electrical safety in case of emergency by
switching off the electrical energy to all or
part of the installation.
EMERGENCY OFF is to be used where a risk
of electric shock or other electrical risk
exists.
EMERGENCY
STOP
Functional safety in an emergency by
bringing a machine or movable parts to a
standstill.
EMERGENCY STOP is used to stop a process
or a motion if this creates a danger.
Table 4.1 EMERGENCY OFF and EMERGENCY STOP as per EN 60204-1
The standard EN 61800-5-2 describes various safety functions that can be used
dependent on the application.
For the position controllers of the CMMS-ST-G2 family, the STO and SS1 safety functions
have been implemented through external circuitry.
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