BECKHOFF TwinSAFE - Manual (Page 95)

Circuit examples
Application Guide TwinSAFE 93
to:
PFH PFH PFH PFH
tot tot tot tot
ൌ ൌ ൌ ൌ 4.20E-09+1.11E-09 + 1.03E-09 + 1.25E-09 + 10%* (1.94E-08+1.94E-08)/2 =
9.53E 9.53E 9.53E 9.53E----09 09 09 09
The MTTF
d
value for block 1 (based on the same assumption) is calculated with:
1
ܯܶܶܨ
ௗ ௧௢௧
= ෍
1
ܯܶܶܨ
ௗ ௡
௡
௜ୀଵ
as:
1
ܯܶܶܨ
ௗ ௧௢௧
=
1
ܯܶܶܨ
ௗ
(ܵݓ݅ݐ݄ܿ݅݊݃ ݉ܽݐ) +
1
ܯܶܶܨ
ௗ
(ܧܮ1904) +
1
ܯܶܶܨ
ௗ
(ܧܮ6900)
+
1
ܯܶܶܨ
ௗ
(ܧܮ2904)
+
1
(ܯܶܶܨ
ௗ
(ܭ1))
with:
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
ܯܶܶܨ
ௗ
(EL6900) =
(1 െ ܦܥ(ܧܮ6900))
ܲܨܪ(ܧܮ6900)
=
(1 െ 0.99)
1.03E െ 09 ଵ
୦
כ 8760 ୦
୷
=
0.01
9.02E െ 06 ଵ
୷
= 1108.6y
ܯܶܶܨ
ௗ
(EL2904) =
(1 െ ܦܥ(ܧܮ2904))
ܲܨܪ(ܧܮ2904)
=
(1 െ 0.99)
1.25E െ 09 ଵ
୦
כ 8760 ୦
୷
=
0.01
1.1E െ 05 ଵ
୷
= 913.2y
MTTF
d tot =
ଵ
భ
మళభ.ళ೤
ା
భ
భబమఴ.ఴ೤
ା
భ
భభబఴ.ల೤
ା
భ
వభయ.మ೤
ା
భ
ఱఴ.వ೤
= 42.3ݕ
DC
avg =
వవ%
మళభ.ళ
ା
వవ%
భబమఴ.ఴ
ା
వవ%
భభబఴ.ల
ା
వవ%
వభయ.మ
ା
వవ%
ఱఴ.వ
ା
వవ%
ఱఴ.వ
భ
మళభ.ళ
ା
భ
భబమఴ.ఴ
ା
భ
భభబఴ.ల
ା
భ
వభయ.మ
ା
భ
ఱఴ.వ
ା
భ
ఱఴ.వ
= 99.0%