BECKHOFF TwinSAFE - Manual (Page 133)

Circuit examples
Application Guide TwinSAFE 131
2.22 Direct wiring of the TwinSAFE outputs to TwinSAFE
inputs (single-channel) (Category 1, PL c)
The output of an EL2904 is wired directly to a safe input of an EL1904; the test pulses and current
measurement of the outputs and the sensor test of the inputs are thereby deactivated. Hence, checks for
cross-circuit and external feed on the cable are not possible.
2.22.1 Parameters of the safe input and output terminals
EL1904
Parameter Value
Sensor test channel 1 active No
Sensor test channel 2 active No
Sensor test channel 3 active No
Sensor test channel 4 active No
Logic channel 1 and 2 Single Logic
Logic channel 3 and 4 Single Logic
EL2904
Parameter Value
Current measurement active No
Output test pulses active No
2.22.2 Block formation and safety loops
2.22.2.1 Block 1
2.22.3 Calculation
2.22.3.1 PFH / MTTF
d
/B10
d
– values
Component Value
EL1904 – PFH 1.11E-09
EL2904 – PFH 1.25E-09
Days of operation (d
op
) 230
Hours of operation / day (h
op
) 8
Cycle time (minutes) (T
cycle
) 60 (1x per hour)
Lifetime (T1) 20 years = 175200 hours
EL6900 EL2904 EL2904 EL1904