BECKHOFF TwinSAFE - Manual (Page 99)

Circuit examples
Application Guide TwinSAFE 97
2.16.3.2 Diagnostic Coverage DC
Component Value
OSSD1/2 with testing (by light curtain) / plausibility DC
avg
=99%
MS1/2/3/4 with testing/plausibility DC
avg
=90%
K1/K2 with testing and EDM DC
avg
=99%
S1 with testing DC
avg
=90%
2.16.3.3 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 8 כ 60
60
ൌ 1840
ܯܶܶܨ
ௗ
ൌ
100000
0.1 כ 1840 ൌ 543.5y ൌ 4761060h
K1/K2:
݊
௢௣
ൌ
230 כ 8 כ 60
60
ൌ 1840
ܯܶܶܨ
ௗ
ൌ
1300000
0.1 כ 1840 ൌ 7065.2 ൌ 61891152h
MS1/MS2/MS3/S4:
݊
௢௣
ൌ
230 כ 8 כ 60
60
ൌ 1840
ܯܶܶܨ
ௗ
ൌ
100000
0.1 כ 1840 ൌ 543.5y ൌ 4761060h
and the assumption that S1, K1 and K2 are in each case single-channel:
ܯܶܶܨ
ௗ
ൌ
1
ߣ
ௗ