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- T1 = Proof test interval (h)
- MTTR = Mean time to restoration (hour)
- MRT = Mean repair time (hour)
- DC = Diagnostic coverage
- β = The fraction of undetected failures that have a common cause
- βD = Of those failures that are detected by the diagnostic tests, the fraction that have a common cause
- βDU = Dangerous Failure rate (per hour) of a channel in a subsystem
- PFDG = Average probability of failure on demand for the group of voted Channels
- PFDS = Average probability of failure on demand for the sensor subsystem
- PFDL = Average probability of failure on demand for the logic subsystem
- PFDFE = Average probability of failure on demand for the final element subsystem
- PFDSYS = Average probability of failure on demand of a safety function for the E/E/PE safety-related system
- PFHG = Probability of failure per hour for the group of voted channels
- PFHS = Probability of failure per hour for the sensor subsystem
- PFHL = Probability of failure per hour for the logic subsystem
- PFHFE = Probability of failure per hour for the final element subsystem
- PFHSYS = Probability of failure per hour of a safety function for the E/E/PE safety-related system
- λ = Total Failure rate (per hour) of a channel in a subsystem
- λD = Dangerous failure rate (per hour) of a channel in a subsystem, equal to 0,5 λ (assumes 50 % dangerous failures and 50 % safe failures)
- λDD = Detected dangerous failure rate (per hour) of a channel in a subsystem (this is the sum of all the detected dangerous failure rates within the channel of the subsystem)
- λDU = Undetected dangerous failure rate (per hour) of a channel in a subsystem (this is the sum of all the undetected dangerous failure rates within the channel of the subsystem)
- λSD = Detected safe failure rate (per hour) of a channel in a subsystem (this is the sum of all the detected safe failure rates within the channel of the subsystem)
- tCE = Channel equivalent mean down time (hour) for 1oo1, 1oo2, 2oo2 and 2oo3 architectures (this is the combined down time for all the components in the channel of the subsystem)
- tGE = Voted group equivalent mean down time (hour) for 1oo2 and 2oo3 architectures (this is the combined down time for all the channels in the voted group)
- tCE’ = Channel equivalent mean down time (hour) for 1oo2D architecture (this is the combined down time for all the components in the channel of the subsystem)
- tGE’ = Voted group equivalent mean down time (hour) for 1oo2D architecture (this is the combined down time for all the channels in the voted group)
- T2 = Interval between demands (h)
- K = Fraction of the success of the auto test circuit in the 1oo2D system
- PTC = Proof Test Coverage
- 1 = High demand or continuous mode only
- 2 = Low demand mode only
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Vikaantumislaskennan kaavoja ja esimerkkejä ~sivu 3,4,5,6,7
1oo1 -arkkitehtuuri
Channel equivalent mean down time (hour)
1oo2 -arkkitehtuuri
Voted group equivalent mean down time (hour)
Average probability of failure on demand for the group of voted Channels
2oo2 -arkkitehtuuri
Average probability of failure on demand for the group of voted Channels
1oo2D -arkkitehtuuri
Channel equivalent mean down time (hour)
Voted group equivalent mean down time (hour)
Average probability of failure on demand for the group of voted Channels
2oo3 -arkkitehtuuri
Average probability of failure on demand for the group of voted Channels
RRF (Risk Reduction Factor) ~sivu 3,4,5,6,7
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