Vega VEGACAL 60 Series, Safety Manual

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9
1 Functional safety
VEGACAL series 60 • Two-wire 4 … 20 mA/HART
35593-EN-181129
The calculations are also based on the specifications stated in chap-
ter " Planning ".
After 8 to 12 years, the failure rates of the electronic components will
increase, whereby the derived PFD and PFH values will deteriorate
(IEC 61508-2, 7.4.7.4, note 3).
Applies to overfill and dry run protection:
λ
sd
0 FIT
λ
su
212 FIT
λ
dd
458 FIT
λ
du
208 FIT
DC
S
0 %
DC
D
68 %
MTBF = MTTF + MTTR 0.93 x 10
6
h
E013 (no measured value available) < 10 sek.
E036/E037 (no executable sensor software) < 1 h
Single channel architecture
SIL SIL2
HFT 0
Instrument type Type B
Applies to overfill and dry run protection:
SFF 76 %
PFD
avg
T
Proof
= 1 year
T
Proof
= 5 years
< 0.091 x 10
-2
< 0.182 x 10
-2
PFH < 0.208 x 10
-6
/h
The chronological sequence of PFD
avg
is nearly linear to the operating
time over a period up to 10 years. The above values apply only to the
T
Proof
interval after which a recurring function test must be carried out.
Service life
Failure rates
Fault reaction time
Specific characteristics
Time-dependent process
of PFD
avg