Example 2: SIL3 (PLe) Safety door opening for maintenance tasks with manual restart. This
function is used to prevent an unexpected restart when a maintenance task is being carried out in a
risk area. In this case, the relay’s safety inputs will be connected to a safety interlock switch placed in
the door. Additionally, a pushbutton will be installed to force a relay manual restart and a lamp
connected to the NC close contact to indicate it.
Example 2- Safety door opening
CAUTION
For SIL 3 applications the safety function has to be tested regularly (approximately once per
month) in order to detect anomalies or possible failures.
According to EN 60204-1 automatic restart is not allowed after an emergency stop. For this reason
the machine control must prevent an automatic start after an emergency stop.
For SIL 3 applications the safety function has to be tested regularly (approximately once per
month) in order to detect certain failures.
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