JUMO 00577948, Safety Manual, Page: 20 / 26

5 Safety-related applications
20
Low-demand mode
The following PFD
avg
values (low demand rate) result from the fault rates.
High-demand mode
The following PFH value (high demand rate) results from the fault rates:
PFH = 6.21 × 10
-8
/h
The requirements when it comes to the PFH value for a SIL2 system are therefore met.
The values for 1, 2, and 3 years mean that the calculated PFD
avg
values are within the permissible range
for SIL2 according to table 2 from IEC/EN 61508-1. They meet the requirement of not covering more
than 10 % of the safety circuit or are better than or equal to 1.00 × 10
-3
.
The values for 4, 5, 6, 7, 8, and 10 years mean that the calculated PFD
avg
values are within the permis-
sible range for SIL2 according to table 2 from IEC/EN 61508-1. However, they do not meet the require-
ment of not covering more than 10 % of the safety circuit/are not better than or equal to 1.00 × 10
-3
.
Failure limit value
The operating mode with a low-demand rate is taken as the basis. The proportion of the device at PFH/
PFD of the entire safety loop is less than 10 %.
5.3 2-channel operation as a repeater power supply and input isolating am-
plifier for SIL3 (1oo2) applications
5.3.1 Safety/integrity requirements
Fault rates
• Type A device (according to IEC/EN 61508-2)
• Safety integrity level (SIL) 3 (1oo2 structure)
• Systematic capability (SC) 3 (1oo2 structure)
• HFT 1
• MTTR 24 h
• MTR 8 h
• Mission time 10 years
• Safety response time 2 s
• Ambient temperature 40 °C
• Proof test coverage (PTC) 97 %
• Process safety time 500 ms
• Switch-on duration 2 s
• ß factor 2 % (Beta D)
Two devices have to be used to achieve a SIL3 level. The two outputs of the devices to the control side
must be connected to the same evaluation unit (PLC/PLS). The evaluation unit must compare the two
values with the max. permissible deviation of 2 % of the input signal.
T [PROOF] 1 year 2 years 3 years 4 years 5 years
PFD
avg
2.73 × 10
-4
5.45 × 10
-4
8.17 × 10
-4
1.09 × 10
-3
1.37 × 10
-3
T [PROOF] 6 years 7 years 8 years 10 years
PFD
avg
1.64 × 10
-3
1.91 × 10
-3
2.18 × 10
-3
2.73 × 10
-3
Safety circuit according to IEC/EN 61508-1
Sensor
Device Processing Actuator
25 % < 10 % 15 % 50 %