Mttf, ܯܶܶܨ, כ 8760 – BECKHOFF TwinSAFE User Manual
Page 114
Circuit examples
112
Application Guide TwinSAFE
If only PFH values are available for EL1904 and EL6900, the following estimation applies:
ܯܶܶܨ
ௗ
ሺELxxxxሻ ൌ
ሺ1 െ ܦܥሺܧܮݔݔݔሻሻ
ܲܨܪሺܧܮݔݔݔሻ
Hence:
ܯܶܶܨ
ௗ
ሺEL1904ሻ ൌ
൫1 െ ܦܥሺܧܮ1904ሻ൯
ܲܨܪሺܧܮ1904ሻ ൌ
ሺ1 െ 0.99ሻ
1.11E െ 09
ଵ
୦
כ 8760
୦
୷
ൌ
0.01
9.72E െ 06
ଵ
୷
ൌ 1028.8y
ܯܶܶܨ
ௗ
ሺEL6900ሻ ൌ
ሺ1 െ ܦܥሺܧܮ6900ሻሻ
ܲܨܪሺܧܮ6900ሻ ൌ
ሺ1 െ 0.99ሻ
1.03E െ 09
ଵ
୦
כ 8760
୦
୷
ൌ
0.01
9.02E െ 06
ଵ
୷
ൌ 1108.6y
ܯܶܶܨ
ௗ
ሺEL2904ሻ ൌ
ሺ1 െ ܦܥሺܧܮ2904ሻሻ
ܲܨܪሺܧܮ2904ሻ ൌ
ሺ1 െ 0.99ሻ
1.25E െ 09
ଵ
୦
כ 8760
୦
୷
ൌ
0.01
1.1E െ 05
ଵ
୷
ൌ 913.2y
MTTF
d tot
=
ଵ
భ
భయఱఴ.ళ
ା
భ
భబమఴ.ఴ
ା
భ
భభబఴ.ల
ା
భ
వభయ.మ
ା
భ
భళలల.య
ା
భ
భబమఴ.ఴ
ൌ 190.7ݕ
DC
avg
=
వవ%
భయఱఴ.ళ
ା
వవ%
మళభళ.ర
ା
వవ%
భబమఴ.ఴ
ା
వవ%
భభబఴ.ల
ା
వవ%
వభయ.మ
ା
వవ%
భళలల.య
ା
వవ%
భళలల.య
ା
వవ%
భబమఴ.ఴ
భ
భయఱఴ.ళ
ା
భ
మళభళ.ర
ା
భ
భబమఴ.ఴ
ା
భ
భభబఴ.ల
ା
భ
వభయ.మ
ା
భ
భళలల.య
ା
భ
భళలల.య
ା
భ
భబమఴ.ఴ
ൌ 99.0%
Notice
Category
This structure is possible up to category 4 at the most.
MTTF
d
Designation for each channel
Range for each channel
low
3 years
≤
MTTF
d
< 10 years
medium
10 years
≤
MTTF
d
< 30 years
high
30 years
≤
MTTF
d
≤
100 years
DC
avg
Designation
Range
none
DC < 60 %
low
90 %
≤
DC < 99 %
medium
90 %
≤
DC < 99 %
high
99 %
≤
DC