Vega VEGAPULS 61, Safety Manual

Page: 7 / 16

T he following assumptions form the basis for the implemen -
tation of
FMEDA :
l
F ailure rates are constant , wear of the mechanical parts is
not taken into account
l
F ailure rates of external power supplies are not taken into
account
l
M ultiple errors are not taken into account
l
T
he average ambient temperature during the operating
time is
40
° C (
104
° F )
l
T
he environmental conditions correspond to an average
industrial environment
l
T he lifetime of the components is around
8
to
12
years
( IEC
61508
-
2
,
7
.
4
.
7
.
4
, remark
3
)
l
T he repair time ( exchange of the measuring system ) after
an nondangerous malfunction is eight hours ( MTTR =
8
h )
l
T he processing unit can interprete
"
fail low
"
and
"
fail high
"
failures as errors and trigger a suitable error message
l
E xisting communication interfaces ( e . g . HART , I
²
C - B us )
are not used for transmission of safety - relevant information
T he measuring system should be used appropriately taking
pressure , temperature , density , dielectric value and chemical
properties of the medium into account .
I nstructions to critical process and vessel situations are
described in the operating instructions manual .
T he user - speci fi c limits must be kept . T he speci fi cations of the
operating instructions manual must not be exceeded .
1 . 3 I nstrument parameter adjustment
S ince the plant conditions in fl uence the safety of the
measuring system , the instrument parameters must be set
according to the application .
T
he following tools are allowed
:
l
the DTM suitable for VEGAPULS in conjunction with an
adjustment software according to the FDT / DTM standard ,
e . g . PACT ware
™
l
I ndicating and adjustment module
N ote :
M ake sure that DTM - C ollection
10
/
2005
or a newer version is
used .
A
ssumptions
G eneral instructions and re -
strictions
A djustment tools
VEGAPULS series
60
-
4
…
20
m A / HART
7
F unctional safety
31338
-
EN
-
070510