Vega VEGACAL 60 Series, Safety Manual

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1 Functional safety
VEGACAL series 60 • Two-wire 4 … 20 mA/HART
35593-EN-181129
Fault signals that may appear are described in the appropriate operat-
ing instructions manual.
If faults or error messages are detected, the entire measuring system
must be shut down and the process held in a safe state by other
measures.
The exchange of the electronics is simple and described in the
operating instructions manual. Note the instructions for parameter
adjustment and setup.
If due to a detected failure the electronics or the complete sensor is
exchanged, the manufacturer must be informed (incl. a fault descrip-
tion).
1.6 Recurring function test
The recurring function test is testing the safety function and to find out
possible undetected, dangerous failuress. The functional capability of
the measuring system has to be tested in adequate time intervals. It
is up to the user's responsibility to selct the kind of testing. The time
intervals are subject to the PFD
avg
-value according to the chart and
diagram in section " Safety-relevant characteristics ".
With high demand rate, a recurring function test is not requested
in IEC 61508. The functional efficiency of the measuring system is
demonstrated by the frequent use of the system. In double channel
architectures it is a good idea to verify the effect of the redundancy
through recurring function tests at appropriate intervals.
Please carry out the test in such a way, that the correct safety function
in combination with all components is granted. This is granted by the
control of the response height during a filling process. If a filling up to
the response height is not practicable, the measuring system has to
be responded by an appropriate simulation of the level or the physical
measuring effect.
The methods and procedures used during the tests must be stated
and their suitability must be specified. The tests must be documented.
If 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.
In a multiple channel architecture this applies separately to each
channel.
1.7 Safety-related characteristics
The failure rates of the electronics, the mechanical parts of the
transmitter as well as the process fitting are determined by an FMEDA
according to IEC 61508. The calculations are based on component
failure rates according to SN 29500. All values refer to an average
ambient temperature during the operating time of 40 °C (104 °F).
For 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 fre-
quent temperature fluctuations are expected.
Reason
Implementation
Basics