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Rockwell Automation Publication SAFETY-AT134B-EN-P - November 2015
Safety Function: Cable Pull Switch with a Configurable Safety Relay
Lifeline 4 Cable Pull Switch Safety Function
This application technique includes two safety functions:
•
Safety-related stop function initiated by a safeguard (Lifeline 4 cable pull switch)
•
Manually-actuated Emergency stop (E-stop)
These safety functions both execute a Stop Category 0 stop.
Safety Function Requirements
Actuating the Lifeline 4 cable pull switch stops and prevents hazardous motion by de-energizing the redundant safety
contactors. When the cable pull switch is de-activated, the 440C-CR30 relay is reset, and no faults are detected, motion
does not resume until a secondary start command is issued by the external start/stop system.
Pressing the E-stop prevents hazardous motion by de-energizing the redundant safety contactors. When the E-stop is de-
activated, the 440C-CR30 relay is reset, and no faults are detected, motion does not resume until a secondary start
command is issued by the external start/stop system.
The safety functions in this application technique each meet or exceed the requirements for Category 3, Performance
Level d (CAT. 3, PLd), per ISO 13849-1 and control reliable operation per ANSI B11.19.
Functional Safety Description
An assembly conveyor needs to be protected from accidental contact with personnel. The risk assessment determined that,
due to the length of the hazardous area, a cable pull switch must be installed to protect the area and to help mitigate the
risk. When the switch is activated, a Stop Category 0 stop takes place on the conveyor motor. The cable pull switch
prevents unexpected startup of the machine while the switch is activated.
An E-stop is also provided to address unanticipated emergency situations. The E-stop is a manually-actuated
complementary safety device. Pressing the E-stop also initiates a Stop Category 0 stop of the conveyor motor. The E-stop
switch prevents unexpected startup of the machine while the E-stop is depressed.
After a safety-related stop, the safety system cannot be reset unless the cable pull switch is reset and the E-stop is released.
Once the safety system is reset, a separate, deliberate action can be used to restart the conveyor with the external start/stop
system.
