Mttf, ܯܶܶܨ, כ 8760 – BECKHOFF TwinSAFE User Manual
Page 81: Category
Circuit examples
Application Guide TwinSAFE
79
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
వబఱ.ఴ
ା
భ
భబమఴ.ఴ
ା
భ
భభబఴ.ల
ା
భ
వభయ.మ
ା
భ
ఱఴ.వ
ା
భ
భబమఴ.ఴ
ൌ 45.4ݕ
DC
avg
=
వవ%
వబఱ.ఴ
ା
వవ%
వబఱ.ఴ
ା
వవ%
భబమఴ.ఴ
ା
వవ%
భభబఴ.ల
ା
వవ%
వభయ.మ
ା
వవ%
ఱఴ.వ
ା
వవ%
ఱఴ.వ
ା
వవ%
భబమఴ.ఴ
భ
వబఱ.ఴ
ା
భ
వబఱ.ఴ
ା
భ
భబమఴ.ఴ
ା
భ
భభబఴ.ల
ା
భ
వభయ.మ
ା
భ
ఱఴ.వ
ା
భ
ఱఴ.వ
ା
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
60 %
≤
DC < 90 %
medium
90 %
≤
DC < 99 %
high
99 %
≤
DC
Category
B
1
2
2
3
3
4
DC
MTTF
d
none
none
low
medium
low
medium
high
low
a
-
a
b
b
c
-
medium
b
-
b
c
c
d
-
high
-
c
c
d
d
d
e