BECKHOFF TwinSAFE User Manual
Page 12
Circuit examples
10
Application Guide TwinSAFE
This produces for the calculation of the PFH value for block 1:
PFHtot= PFH(S1) + PFH(EL1904) + PFH(EL6900) + PFH(EL2904) +
β
* (PFH(K1)+
PFH(K2))/2 + PFH(S2) + PFH(EL1904)
Since the portion
(PFH(K1)* PFH(K2))*T1
is smaller than the rest by the power of ten, it is neglected
in this and all further calculations for the purpose of simplification.
to:
PFH
PFH
PFH
PFH
tot
tot
tot
tot
=
==
=
2.50E-11 + 1.11E-09 + 1.03E-09 + 1.25E-09 + 10% * (7.96E-11+7.96E-11)/2 =
3.42E
3.42E
3.42E
3.42E----09
09
09
09
in the case of actuation 1x per week
or
PFH
PFH
PFH
PFH
tot
tot
tot
tot
=
==
=
2.50E-11+1.11E-09 + 1.03E-09 + 1.25E-09 + 10% * (1.92E-11+1.92E-11)/2=
3.42E
3.42E
3.42E
3.42E----09
09
09
09
in the case of actuation 1x per shift
The MTTF
d
value for block 1 (based on the same assumption) is calculated with:
1
ܯܶܶܨ
ௗ ௧௧
=
1
ܯܶܶܨ
ௗ
ୀଵ
as:
1
ܯܶܶܨ
ௗ ௧௧
=
1
ܯܶܶܨ
ௗ
(ܵ1) +
1
ܯܶܶܨ
ௗ
(ܧܮ1904) +
1
ܯܶܶܨ
ௗ
(ܧܮ6900) +
1
ܯܶܶܨ
ௗ
(2904)
+
1
(ܯܶܶܨ
ௗ
(ܭ1))
with:
ܯܶܶܨ
ௗ
(S1) =
ܤ10
ௗ
(ܵ1)
0.1 כ ݊
ܯܶܶܨ
ௗ
(K1) =
ܤ10
ௗ
(ܭ1)
0.1 כ ݊
If only PFH values are available for EL1904 and EL6900, the following estimation applies:
ܯܶܶܨ
ௗ
(ELxxxx) =
(1 െ ܦܥ(ܧܮݔݔݔ))
ܲܨܪ(ܧܮݔݔݔ)
Hence:
ܯܶܶܨ
ௗ
(EL1904) =
൫1 െ ܦܥ(ܧܮ1904)൯
ܲܨܪ(ܧܮ1904) =
(1 െ 0.99)
1.11E െ 09
ଵ
୦
כ 8760
୦
୷
=
0.01
9.72E െ 06
ଵ
୷
= 1028.8y