
Rockwell Automation Publication 1756-UM013B-EN-P - October 2019
131
Safety Data for Safety Modules
Appendix D
1756-OBV8S Safety Data
lists the safety data for the 1756-OBV8S module.
Table 9 - 1756-OBV8S Module Safety Data
Attribute
Output Mode
Sourcing
Bipolar
Point Operation Type
Point Operation Type
Single
Dual
Single
Safety Function Architecture (HFT)
0
1
1
Safe Failure Rate (
λ
s
) [failures/hr]
1.16E-06
9.3E-07
9.5E-07
Safe Detected Failure Rate (
λ
SD
)
(1)
1.16E-06
9.3E-07
9.5E-07
Safe Undetected Failure Rate (
λ
SU
)
4.23E-10
5E-10
4.9E-10
Dangerous Failure Rate (
λ
D
) [failures/hr]
9.01E-07
5.9E-07
6.1E-07
Dangerous Detected Failure Rate (
λ
DD
) [failures/hr]
9.01E-07
5.9E-07
6.1E-07
Dangerous Undetected Failure Rate (
λ
DU
) [failures/hr]
3.29E-10
3.1E-10
3.1E-10
SRT [millisecond]
4.5
Automatic Diagnostic Test Interval (TD) [hr]
4
Useful Life [yr]
20
Systematic Capability (SC)
3
Safe Failure Fraction (SFF) [%]
99.98%
99.98%
99.98%
PFH
3.29E-10
3.1E-10
3.1E-10
PFD
AVE
10 yrs
1.44E-05
1.4E-05
1.4E-05
Mission Time™
20 yrs
2.89E-05
2.8E-05
2.8E-05
Diagnostic Coverage Average (DC
AVE
)
99.96%
99.95%
99.95%
Spurious Trip Rate (STR)
3.99E-06
2.68E-06
2.79E-06
MTTF [years]
55.50
75.09
72.91
MTTF
D
[years]
126.69
194.80
186.19
(1) (
λ
SD) and (
λ
SU) are calculated with assumption of Diagnostic Coverage of Safe Failure is same as Diagnostic Coverage of Dangerous Failure
Summary of Contents for 1756 Series
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