C1250 Installation Guide
DC (Diagnostic Coverage) is high (99%) assuming that the state of the feedback contacts
is checked after each change of the state of the control contacts.
MTTFd mainly depends on the number of operations of the safety relays.
Example calculation of MTTFd:
Assuming that the safety function is requested every 20s on a machine running 24h per
day and 7 days per week.
B
10
= 10'000'000
B
10d
= 20'000'000 (according EN ISO 13849-1:2008 table C.1)
n
op
= (24h/Tag*365.25Tage/Jahr*3600s/h) / 20s = 1'577'880 operations per year
MTTF
d
= B
10d
/ (0.1 x n
op
) = 126.75 years (this has to be limited to 100years
according the standard for further calculations)
= high (100 years)
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