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Motor-protective circuit-
breaker PKE12 and PKE32
48
06/10 MN03402004Z-DE/EN
Determining the rate of hazardous undiscovered
failures
• The sum of the rate of undiscovered hazardous failures for
trip blocks and basic devices at 40 °C ambient air
temperature is calculated as follows:
• The sum of the rate of undiscovered hazardous failures for
trip blocks and basic devices at 60 °C ambient air
temperature and self-heating is calculated as follows:
7.11 x 10
-7
/h - 4.73 x 10
-7
/h = 238 FIT
7.245 x 10
-7
/h - 4.284 x 10
-7
/h = 296 FIT
238 FIT + 296.1 FIT = 534.1 FIT
Total =
5.341 x 10
-7
/h
7.402 x 10
-7
/h - 4.916 x 10
-7
/h = 248.6 FIT
7.245 x 10
-7
/h - 4.284 x 10
-7
/h = 296.1 FIT
248.6 FIT + 296.1 FIT = 544.7 FIT
Total =
5.447 x 10
-7
/h
h
The rate of undiscovered hazardous failures therefore lies
below the 10
-6
/h threshold, fulfilling the requirements for
SIL 2.
Summary of Contents for PKE12 Series
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