Yokogawa EJX440A - Manual (Page 46)

<4. Diagnostics>
4-6
IM 01C25T01-01E
If “Large Fluct L” or “Large Fluct H” is detected,
consider whether a blockage result is correct.
The threshold values to detect large fluctuation are
set to Lim fSPlmax and Lim fSPhmax.
Since these values are enough to detect large
fluctuation, it is not almost necessary to change
them.
4.2.2.2 Combination of Reference Result
and Blockage Detection
An EJX differential pressure transmitter can detect
four modes of impulse line blockage: both-sides,
high-pressure side, low-pressure side, and/or
single-side when all the reference values are
properly measured. However, the detectable alarm
mode combination is limited when some of the
reference values are invalid. Available Blockage
Detection are shown in the below figure.
NOTE
• Ref fDP must be larger than the specified
level shown in Table 4.2.4 (refer to 4.2.2.6).
No blockage can be detected when Ref fDP
is not large enough.
• The plausibility of blockage detection needs
to be confirmed by blockage simulation test.
The simulation test can be performed by
the appropriate manifold operation (refer to
4.2.2.8).
[Transmitter for gauge/absolute pressure and level measurement]
[Differential pressure transmitter]
Ref fDP: OK
Ref SPI: OK
Ref SPh: OK
Ref BlkF: OK
Fluctuation Parameters
• Test for low-pressure side
• Test for high-pressure side
• Test for both-pressure sides
Simulation Test
• B Blocking detection
(by using Ratio fDP)
• L Side Blocking detection
(by using Ratio fSPI)
• H Side Blocking detection
(by using Ratio fSPh)
• H/L Side Blocking detection
(by using BlkF)
Ref fDP: OK
Ref SPI: OK
Ref SPh: OK
Ref BlkF: NG
• Test for low-pressure side
• Test for high-pressure side
• Test for both-pressure sides
• A/B Blocking detection
(by using Ratio fDP)
• L Side Blocking detection
(by using Ratio fSPl)
• H Side Blocking detection
(by using Ratio fSPh)
Ref fDP: OK
Ref SPI: NG
Ref SPh: OK
Ref BlkF: NG
• Test for high-pressure side
• A Blocking detection
(by using Ratio fDP)
• H Side Blocking detection
(by using Ratio fSPh)
Ref fDP: OK
Ref SPI: NG
Ref SPh: NG
Ref BlkF: NG
• Test for both-pressure sides
• B Blocking detection
(by using Ratio fDP)
Available Blockage Detection
Ref fDP: OK
Fluctuation Parameters Simulation Test
• Test for high-pressure side
• B Blocking detection
(by using Ratio fDP)
Available Blockage Detection
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