KROHNE OPTISWITCH 5xx0C 2wire SIL EN - Manual (Page 8)

This is ensured by a controlled reaching of the response height during
filling. If filling 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 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 the double channel architecture (1oo2D) this applies separately to
both channels.
If the measuring system is used as overfill protection, the proof of the
function is ensured by a simple function test which can be triggered
and monitored manually or by a connected control system.
This function test is triggered by an interruption of the supply cable for
at least two seconds. Then a special warm-up reaction of the current
output is carried out which must be recorded.
The test procedure is described in detail in the operating instructions
manual.
Test key on the signal conditioning instrument:
If a connected signal conditioning instrument with test key is used for
processing, the stated function test can be easily carried out by
pushing the test key. Suitable signal conditioning instruments are listed
in chapter "Technical data" of the operating instructions manual.
This test can be carried out only if the vibrating element is uncovered.
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
frequent temperature fluctuations are expected.
The calculations are also based on the specifications stated in chapter
"P
lanning".
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).
Function test in mode
overfill protection
Basics
Service life
8 OPTISWITCH series 5000 • - two-wire
1 Functional safety
32750
-EN
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