Safety Integrity Level SIL3- PLe
This configuration provides a highly reliable safety level. When the sensor is activated due to an
emergency situation, the STO function interrupts the power supply to the motor. The motor will stop for
its own inertia or will prevent an accidentally start.
The sensors (emergency push buttons, limit switches, etc.) must be certified as safety elements.
The value of the average probability of a dangerous failure per hour (PFH) of all elements applicable
to the safety function, must not exceed the limit of the corresponding SIL level. The installation must
be performed by trained personal with experience in functional safety.
Example 1: Safety function with automatic restart by emergency stop buttons (SIL3, PLe). It is
mandatory that the stop button has 2 closed contacts (NC) that will be connected to the safety inputs
of the relay.
Example 1- Emergency stop push button
CAUTION
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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