BECKHOFF TwinSAFE - Manual (Page 41)

Circuit examples
Application Guide TwinSAFE 39
2.6.3.3 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
10080
ൌ 21.90
ܯܶܶܨ
ௗ
ൌ
100000
0.1 כ 21.90
ൌ 45662.1y ൌ 399999120h
S2:
݊
௢௣
ൌ
230 כ 16 כ 60
10080
ൌ 21.90
ܯܶܶܨ
ௗ
ൌ
10000000
0.1 כ 21.90
ൌ 4566210.0y ൌ 4E10h
K1/K2:
݊
௢௣
ൌ
230 כ 16 כ 60
10080
ൌ 21.90
ܯܶܶܨ
ௗ
ൌ
1300000
0.1 כ 21.90
ൌ 593607.3y ൌ 5199997320h
and the assumption that S1, S2, K1 and K2 are in each case single-channel:
ܯܶܶܨ
ௗ
ൌ
1
ߣ
ௗ
results in a
ܲܨܪ ൌ
0.1 כ ݊
௢௣
כ ሺ1 െ ܦܥሻ
ܤ10
ௗ
ൌ
1 െ DC
MTTF
ୢ
S1:
ܲܨܪ ൌ
1 െ 0.99
45662.1 כ 8760
ൌ 2.50E െ 11
S2:
ܲܨܪ ൌ
1 െ 0.90
4566210.0 כ 8760
ൌ 2.50E െ 12
K1/K2:
actuation 1x per shift and direct feedback
ܲܨܪ ൌ
1 െ 0.99
593607.3 כ 8760
ൌ 1.92E െ 12