Vega VEGAPULS 61 Safety manual - page 7
The following assumptions form the basis for the implemen-
tation of FMEDA:
l
Failure rates are constant, wear of the mechanical parts is
not taken into account
l
Failure rates of external power supplies are not taken into
account
l
Multiple errors are not taken into account
l
The average ambient temperature during the operating
time is 40 °C (104 °F)
l
The environmental conditions correspond to an average
industrial environment
l
The lifetime of the components is around 8 to 12 years
(IEC 61508-2, 7.4.7.4, remark 3)
l
The repair time (exchange of the measuring system) after
an nondangerous malfunction is eight hours (MTTR = 8 h)
l
The processing unit can interprete "fail low" and "fail high"
failures as errors and trigger a suitable error message
l
Existing communication interfaces (e.g. HART, I²C-Bus)
are not used for transmission of safety-relevant information
The measuring system should be used appropriately taking
pressure, temperature, density, dielectric value and chemical
properties of the medium into account.
Instructions to critical process and vessel situations are
described in the operating instructions manual.
The user-specific limits must be kept. The specifications of the
operating instructions manual must not be exceeded.
1
.3 Instrument parameter adjustment
Since the plant conditions influence the safety of the
measuring system, the instrument parameters must be set
according to the application.
The following tools are allowed:
l
the DTM suitable for VEGAPULS in conjunction with an
adjustment software according to the FDT/DTM standard,
e.g. PACTware™
l
Indicating and adjustment module
Note:
Make sure that DTM-Collection 10/2005 or a newer version is
used.
Assumptions
General instructions and re-
strictions
Adjustment tools
VEGAPULS series 60 - 4 … 20 mA/HART
7
Functional safety
31338
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EN
-070510