KROHNE DK 32-DK 34-DK 37 Safety V1 EN - Manual (Page 12)

7
SAFETY-RELATED CHARACTERISTICS
12
DK32 - DK34 - DK37
www.krohne.com 02/2012 - 4000574702 MA DK32 34 37 SIL R02 en
7.2 Specific safety-related characteristics
Under the assumptions described in 7.1 and the definitions given in section 4 the following tables
show the failure rates according to IEC 61508:
DK32 DK32 DK32 DK32/K*...-SK with 1 or 2 fail-safe limit switches 1
Fail safe Fail dangerous
detected undetected detected undetected
λ
SD
λ
SU
λ
DD
λ
DU
SFF 2 SIL AC 3
Stress profile 2 0 FIT 238 FIT 0 FIT 97 FIT 71.0% SIL2
Stress profile 4 0 FIT 300 FIT 0 FIT 136 FIT 68.7% SIL2
T[Proof] 4 1 year 5 years 10 years
PFD
AVG
5 4.63*10 -4 2.15*10 -3 4.25*10 -3
1 The switching contact output is connected to a fail-safe NAMUR amplifier (e.g. Pepperl
& Fuchs KF**-SH-Ex1). The failure rates of the amplifier are not included in the listed
failure rates.
2 The number listed is for reference only. The SFF must be determined for the complete
subsystem.
3 SIL AC (architectural constraints) means that the calculated values are within the range
for hardware architectural contraints for the corresponding SIL level.
4 It is assumed that proof testing is performed with a proof test coverage of 99%.
5 The PFD
AVG
was calculated for profile 2 using the Markov modelling. The results must
be considered in combination with PFD
AVG
values of other devices of the Safety
Instrumented Function (SIF) in order to determine suitability for a specific Safety
Integrity Level (SIL)
For SIL1 applications, the PFD
AVG
value needs to be < 10 -1 .
For SIL2 applications, the PFD
AVG
value needs to be < 10 -2 .
MA_DK32_34_37_SIL_R02_en_574702_PRT.book Page 12 Thursday, March 1, 2012 9:53 AM