4
Product
Description
EDBC250SIO | 2.0
137
4.7
Safety-related Ratings of a Two-channel Application
The table below lists the safety-related ratings of a two-channel safety function that uses two
inputs and/or two outputs of the safe I/O module.
Note: All components involved in the safety function must be taken into account in order to
assess whether the desired safety level is achieved.
Safety-related ratings of a two-channel application
Highest safety integrity level
to EN 62061
SIL3
Highest safety integrity level
to IEC 61508
SIL3
Highest performance level
to EN ISO 13849-1
Cat. 4/PL e
Hardware fault tolerance (HFT) in single-channel ap-
plication
(IEC 61508)
1
(a fault of the application need not cause the safeguard to fail)
Safety-related ratings of a two-channel application
Safety-related ratings
Ambient mo-
dule tempera-
ture
1x input
(up to fieldbus)
Logic circuitry
1x output
(from fieldbus)
Probability of failure on demand
(PFDavg), proof test interval: 20
years (IEC 61508)
25 °C
7.51 * 10
-9
4.01 * 10
-6
1.27 * 10
-8
55 °C
2.94 * 10
-8
9.00 * 10
-6
4.09 * 10
-8
Probability of failure per hour
(PFH), proof test interval: 20 years
(IEC 61508)
25 °C
8.57 * 10
-13
1/h
4.58 * 10
-10
1/h
1.45 * 10
-12
1/h
55 °C
3.35 * 10
-12
1/h
1.03 * 10
-9
1/h
4.66 * 10
-12
1/h
DC (diagnostic coverage)
to EN ISO 13849-1
25 °C
99.00 %
98.14 %
99.00 %
55 °C
99.00 %
97.38 %
99.00 %
Safe failure fraction (SFF)
25 °C
99.83 %
99.04 %
99.68 %
55 °C
99.79 %
98.95 %
99.68 %
MTTF d (Mean Time To Failure dan-
gerous) to EN ISO 13849-1
25 °C
100 years
(calc.: 13341 years)
100 years
(calc.: 226 years)
100 years
(calc.: 9110 years)
55 °C
100 years
(calc.: 3425 years)
100 years
(calc.: 197 years)
100 years
(calc.: 2982 years)
The safety-related ratings are calculated by combining the values of inputs, logic circuitry and
outputs to describe their interdependency with the safety function. The rule is to combine the
logic circuitry with the relevant number of inputs or outputs once per safe I/O module.
Examples of two-channel safety functions:
•
1x logic & 2x input = safety rating of the module from the pair of inputs to the fieldbus.
•
1x logic & 2x output = safety rating of the module from the fieldbus to the pair of outputs.
•
2x input & 1x logic & 2x output = safety rating of pairs of outputs
