BECKHOFF TwinSAFE - Manual (Page 13)

Circuit examples
Application Guide TwinSAFE 11
ܯܶܶܨ
ௗ
ሺEL6900ሻ ൌ
൫1 െ ܦܥሺܧܮ6900ሻ൯
ܲܨܪሺܧܮ6900ሻ
ൌ
ሺ1 െ 0.99ሻ
1.03E െ 09 ଵ
୦
כ 8760 ୦
୷
ൌ
0.01
9.02E െ 06 ଵ
୷
ൌ 1108.6y
ܯܶܶܨ
ௗ
ሺEL2904ሻ ൌ
൫1 െ ܦܥሺܧܮ2904ሻ൯
ܲ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
రఱలలమ.భ೤
ା
భ
భబమఴ.ఴ೤
ା
భ
భభబఴ.ల೤
ା
భ
వభయ.మ೤
ା
భ
ఱవయలబళ.య೤
ൌ 333.98ݕ
DC
avg =
వవ%
రఱలలమ.భ
ା
వవ%
భబమఴ.ఴ
ା
వవ%
భభబఴ.ల
ା
వవ%
వభయ.మ
ା
లబ%
ఱవయలబళ.య
ା
లబ%
ఱవయలబళ.య
భ
రఱలలమ.భ
ା
భ
భబమఴ.ఴ
ା
భ
భభబఴ.ల
ା
భ
వభయ.మ
ା
భ
ఱవయలబళ.య
ା
భ
ఱవయలబళ.య
ൌ 98.96%
or:
DC
avg =
వవ%
రఱలలమ.భ
ା
వవ%
భబమఴ.ఴ
ା
వవ%
భభబఴ.ల
ା
వవ%
వభయ.మ
ା
వబ%
ఱవయలబళ.య
ା
వబ%
ఱవయలబళ.య
భ
రఱలలమ.భ
ା
భ
భబమఴ.ఴ
ା
భ
భభబఴ.ల
ା
భ
వభయ.మ
ା
భ
ఱవయలబళ.య
ା
భ
ఱవయలబళ.య
ൌ 98.99%
CAUTION
Measures for attaining category 3!
This structure is possible up to category 3 at the most, since an error in the feedback
path of the relays may be undiscovered. In order to attain category 3, all rising and
falling edges must be evaluated together with the time dependence in the controller for
the feedback expectation!
CAUTION
Implement a restart lock in the machine!
The restart lock is NOT part of the safety chain and must be implemented in the
machine!
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