kcd2-sr--ex- Pepperl+Fuchs, kcd2-sr--ex- Datasheet - Page 6

• Manufacturer Part Number: kcd2-sr--ex-
• Description: Process Automation
• Manufacturer: Pepperl+Fuchs

2
2.1
2.1.1
2.1.2
2.2
6
SAFETY MANUAL SIL KCD2-SR-(EX)*.(LB), HIC282*
Planning
Planning
System Structure
Definition Low Demand Mode
If there are two loops, one for the standard operation and another one for the functional safety,
then usually the demand rate for the safety loop is assumed to be less than once per year.
The relevant safety parameters to be verified are:
•
•
•
Definition High Demand Mode
If there is only one loop, which combines the standard operation and safety related operation,
then usually the demand rate for this loop is assumed to be higher than once per year.
The relevant safety parameters to be verified are:
•
•
•
•
Assumptions
The Hardware assessment consists of a Failure Modes, Effects and Diagnostics Analysis
(FMEDA). From the FMEDA, failure rates are determined and consequently the
Safe Failure Fraction (SFF) is calculated for the device.
The following assumptions have been made during the FMEDA analysis:
•
•
•
•
the PFD
that has a direct impact on the PFD
PFH (Probability of dangerous Failure per Hour)
Fault reaction time of the safety system
the SFF value (Safe Failure Fraction)
the HFT architecture (Hardware Fault Tolerance architecture)
Failure rates are constant, wear out mechanisms are not included.
The device shall claim less than 10 % of the total failure budget for a SIL2 safety loop.
For a SIL2 application operating in Low Demand Mode the total PFD
SIF (Safety Instrumented Function) should be smaller than10
allowable PFD
The stress levels are average for an industrial environment and can be compared to the
Ground Fixed Classification of MIL-HNBK-217F. Alternatively, the assumed environment is
similar to:
the SFF value (Safe Failure Fraction)
the HFT architecture (Hardware Fault Tolerance architecture)
•
avg
IEC 60654-1 Class C (sheltered location) with temperature limits within the
manufacturer's rating and an average temperature over a long period of time of
40 ºC. Humidity levels are assumed within manufacturer's rating. For a higher
average temperature of 60 ºC, the failure rates should be multiplied with an
experience based factor of 2.5. A similar multiplier should be used if frequent
temperature fluctuation must be assumed.
value (average Probability of Failure on Demand) and T
avg
value would then be 10
avg
)
-3
.
-2
, hence the maximum
proof
avg
(proof test interval
value of the