7.9.10.2 SIL CL3 / PLe Dual Channel control
To achieve PLe / SIL CL3, the safe switching of the pulse inhibitor must be tested peri-
odically by analyzing the feedback signal from a safety control:
At the start of a system
At the restart after triggering a protective device
At least every 8 hours by the operator.
The inputs STO1-ENABLE and STO2-ENABLE are switched in turns according to a defined
test sequence. The switching states of the pulse inhibitor are available at the status outputs
of the S748/772 and are analyzed by a safety control.
The test sequence for the functional test of the safe pulse inhibitor must be performed as
shown in the following time chart.
Prerequisites for the start of the test sequence:
Operational readiness BTB/RTO = “1"
Enable signal ENABLE = “0"
STO1-ENABLE and STO2-ENABLE = “0"
Legend:
STO1-ENABLE: digital input, 1st switch-off path
STO1-STATUS: digital output, switching state of pulse
inhibitor 1st switch-off path
Start: Start of test sequence
STO2-ENABLE: digital input, 2nd switch-off path
STO2-STATUS: digital output, switching state of pulse
inhibitor 2nd switch-off path
T1 bis T5: Test sequence
End: End of test sequence
S748-772 Instructions Manual | 7 Technical description
Kollmorgen | kdn.kollmorgen.com | July 2019 51
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