Vega VEGAPULS 61, Safety Manual

Page: 10 / 16

T he test must be carried out in a way that veri fi es the fl awless
operation of the safety functions in conjunction with all system
components
.
T his is ensured by a controlled reaching of the response height
during fi lling . I f fi lling up to the response height is not possible ,
then a response of the measuring system must be triggered by
a suitable simulation of the level or the physical measuring
e
ff ect
.
T he methods and procedures used during the tests must be
stated and their suitability must be speci fi ed . T he tests must be
documented .
I f the function test proves negative , the entire measuring
system must be switched out of service and the process held
in a safe state by means of other measures
.
I
n the double channel architecture
1
oo
2
D
this applies
separately to both channels .
1
.
7
S afety - related characteristics
T he failure rates of the electronics , the mechanical parts of the
transmitter as well as the process fi tting are determined by an
FMEDA according to IEC
61508
. T he calculations are based
on component failure rates according to SN
29500
. A ll values
refer to an average ambient temperature during the operating
time of
40
° C (
104
° F ).
F
or a higher average temperature of
60
°
C (
140
°
F ),
the failure
rates should be multiplied by a factor of
2
.
5
. A similar factor
applies if frequent temperature fl uctuations are expected .
T he calculations are also based on the speci fi cations stated in
chapter " P lanning " .
A fter
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
).
A pplies to over fi ll and dry run protection :
λ
sd
0
FIT
λ
su
461
FIT
λ
dd
1129
FIT
λ
du
358
FIT
DC
S
0
%
B asics
S ervice life
F ailure rates
10
VEGAPULS series
60
-
4
…
20
m A / HART
F unctional safety
31338
-
EN
-
070510