1.5.1.4.3.5 Use cases
STO-SBC use cases are not limited to the cases presented in this section:
1.5.1.4.3.5.1 Emergency stop
The STO and SBC functions can be used for implementing the category 0 emergency stop function
according to IEC 60204-1:2016.
Emergency stop function can be done
With an emergency stop switch connected directly to control the STO-SBC input signals
With an emergency stop relay + emergency stop switch. STO-SBC feedback signal can be utilized to
make monitored manual start/restart
With safety PLC + emergency stop switch. STO-SBC feedback signal can be utilized to make
monitored, manual start/restart
Please read the section about the working principle of the safety functions.
All cases above require correct behaviour from the controlling PLC (can be a non-safety PLC). After resetting
the emergency stop function, a separate and deliberate action must be used to restart the system.
Attention
IEC 60204-1:2016 requires “reset shall not initiate a restart” regarding emergency stop.
1.5.1.4.3.5.2 Prevention of unexpected start-up
STO and SBC function can be used when power removal is required to prevent an unexpected start-up
according to ISO 14118. A lockable safety switch for activating the STO-SBC function is required.
The function “Prevention of unexpected start-up” can be used for system maintenance activities (e.g.
Repairing/cleaning activities inside hazardous areas)
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