BECKHOFF TwinSAFE - Manual (Page 65)

Circuit examples
Application Guide TwinSAFE 63
2.10.3 Calculation
2.10.3.1 PFH / MTTF
d
/B10
d
– values
Component Value
EL1904 – PFH 1.11E-09
EL2904 – PFH 1.25E-09
EL6900 – PFH 1.03E-09
S1 – B10
d
1,000,000
S2 – B10
d
2,000,000
S3 – B10
d
20,000,000
S4 – B10
d
20,000,000
K1 – B10
d
1,300,000
K2 – B10
d
1,300,000
Days of operation (d
op
) 230
Hours of operation / day (h
op
) 16
Cycle time (minutes) (T
cycle
) 15 (4x per hour)
Lifetime (T1) 20 years = 175200 hours
2.10.3.2 Diagnostic Coverage DC
Component Value
S1/S2 with testing/plausibility DC
avg
=99%
S3/S4 with without testing / with plausibility DC
avg
=90%
K1/K2 with testing and EDM DC
avg
=99%
2.10.3.3 Calculation for block 1
Calculation of the PFH and MTTF
d
values from the B10
d
values:
From:
݊
௢௣
ൌ
݀
௢௣
כ ݄
௢௣
כ 60
ܶ
஼௬௖௟௘
and:
ܯܶܶܨ
ௗ
ൌ
ܤ10
ௗ
0.1 כ ݊
௢௣
Inserting the values, this produces:
S1:
݊
௢௣
ൌ
230 כ 16 כ 60
15
ൌ 14720
ܯܶܶܨ
ௗ
ൌ
1000000
0.1 כ 14720
ൌ 679.3y ൌ 5951087h