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SPECIFICATION OF SAFETY FUNCTION
6
6.1 Preliminary requirements
WARNING!
The data in this supplement only contains the data applicable to the SIL approval. The technical
data for the standard version in the handbook (document [N1]) shall be valid in its current
version, provided that it is not rendered invalid or replaced by this supplement.
6.2 Definition of the safety function
6.2.1 General notes
The device contains a safety function that agrees with the international standard IEC 61508
(document [N2]). This safety function operates if there is a large difference between the level
measurement and the level shown as a current output.
If the device finds that there is a difference of more than 2.5%of the 4...20 mA range between the
level measurement and the level shown as a current output, then the current output changes to
an error signal in less than 30 seconds. The safety integrity level of this safety function is SIL2.
INFORMATION!
If menu item 2.4.5 ERROR DELAY = 0 s, then the current output changes to an error signal in less
than 30 seconds. If menu item 2.4.5 ERROR DELAY is more than 0 seconds, then the current
output changes to an error signal in 30 seconds + 2.4.5 ERROR DELAY.
After the device finds an error, it will try to measure the level of the product again. If the device
can measure the level, the error signal will change to the measurement signal. If the device
continues to have the same problem, the output current will change to the error signal. If, after
30 seconds, the output current is not 3.6 mA then the error is recorded as a "dangerous
undetected failure" in the FMEDA analysis. If, after 30 seconds, the output current is 3.6 mA then
the error is recorded as a "dangerous detected failure" in the FMEDA analysis.
6.2.2 Limits of application
This version of the device has the restrictions that follow:
• Distance is measured in Direct mode
• Only the compact version (the signal converter is attached directly to the antenna) can be
used.
• It is a 2-wire loop-powered device.
• HART® communication is not permitted when you use the safety function.
• The process safety time must be more than 33 minutes. This minimum time agrees with
International Standard IEC 61508 Part 2 (document [N2]), section 7.4.4.1.4.
• Use DN80 and DN100 Metallic Horn antenna only in stilling wells as specified in the handbook
(document [N1]).
For more data, refer to
11
Direct mode (only one product in the tank is permitted).
Direct mode
Direct mode
SIL-specific technical data
www.drexelbrook.com
on page 29.
DR5200
DR5200-LM SIL2 Issue 2
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