Instruction Manual PROTECT-PSC
V 2.6R01 / 04.19
1
–10
1.8
Safety Integrity Level
The Safety Integrity Level (SIL) to IEC 61508 is one of 4 levels to specify the
requirements of safety integrity of the safety functions which are assigned to all
elements of the chain. Level 4 is the highest and level 1 the lowest safety integrity
level.
The Safety Integrity Level is defined for the following operating modes:
low demand rate :
whereby the rate of demand to the safety related system is no
more from once per year and is no greater than double the frequency of the repeat
check.
with high demand rate/continuous demand :
whereby the rate of demand to the
safety related system is more than once per year or is greater than double the
frequency of the repeat check.
The average probability of a failure of a safety function with low demand rate is
specified by the PFD factor (average probability of failure to perform its design
function on demand).
The average probability of a failure with a function with high/continuous demand
rate is specified by the PFH factor (average probability of a dangerous failure per
hour).
The following is an overview of the PROTECT-PSC values.
Safety function : One two-channel safety input affects one dual channel
safety output
Demand rate
Failure probability
low
PFD = 3.0 * 10
-4
high/continuous
PFH = 1.5 *10
-8
/h
Safety function : Two two-channel safety inputs affect one dual channel
safety output
Demand rate
Failure probability
low
PFD = 3.4 * 10
-4
high/continuous
PFH = 1.9 * 10
-8
/h
Safety function : One single-channel safety inputs affect one dual-channnel
safety output
Demand rate
Failure probability
high/continuous
PFH = 2.5 * 10
-7
/h
Safety function: One single-channel safety inputs affect one single-channel
semiconductor safety output
Demand rate
Failure probability
high/continuous
PFH = 4.8 * 10
-7
/h
T
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The PROTECT-PSC is suitable for SIL 3 safety functions due to the restrictions of
the hardware’s safety integrity:
•
SFF
= 99.0%
•
Hardware error tolerance = 1,
•
Type B partial system
for SIL 3 safety functions suitably.
Summary of Contents for PROTECT-PSC
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Page 265: ...Annex 8 Instruction Manual PROTECT PSC V 2 6R01 04 19 8 5 8 3 EC Type Examination certificate ...
Page 266: ...Annex 8 Instruction Manual PROTECT PSC V 2 6R01 04 19 8 6 8 4 Declarations of conformity W ...
Page 267: ...Annex 8 Instruction Manual PROTECT PSC V 2 6R01 04 19 8 7 8 5 Index ...
