Manual

<Appendix 8. Advanced Diagnostics>
A8-4
IM 01C25R03-01E
 High/Low Side Blocking Detection
EJX differential pressure transmitter enables
to detect both-, a high-, or low-pressure-side
blockage. The blockage degree characterized
by a comparison of high-pressure side and low-
pressure-side uctuation values, VALUE_BLKF, is
used to detect it. The value changes within a range
of –1 to +1. As VALUE_BLKF approaches +1, the
high-pressure-side blockage progresses. On the
other hand, if it approaches -1, the low-pressure-
side blockage progresses.
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0
1
0
FA0803.ai
VALUE_BLKF
Blockage detection for
high-pressure side
Threshold
Blockage Progress
VALUE_BLKF
Blockage detection for
low-pressure side
Threshold
Blockage Progress
-1-1
Figure A8.2 Relation between Blockage Progress
and VALUE_BLKF
The each threshold value to detect the high- or
low-pressure-side blockage is set to DIAG_LIM [7]
or [8].
 Low Side Blocking Detection
VALUE_BLKF is preferentially used to "Low Side
Blocking" detection. If VALUE_BLKF cannot
be used, RATIO_FSPL, SQRT (VALUE_FSPL
/ REFERENCE_FSPL) is used to "Low Side
Blocking" detection. REFERENCE_FSPL is
the average value of the sum of squares of low-
pressure-side static pressure uctuations under
normal condition. As the value of RATIO_FSPL
is below the value of DIAG_LIM [4], EJX gives an
alarm of "Low Side Blocking". On the other hand, if
this value exceeds the value of DIAG_LIM [3], EJX
gives an alarm of “Large Fluctuation of Low Side”.
 High Side Blocking Detection
VALUE_BLKF is preferentially used to "High
Side Blocking" detection. If VALUE_BLKF cannot
be used, RATIO_FSPH, SQRT (VALUE_FSPH
/ REFERENCE_FSPH) is used to "High Side
Blocking" detection. REFERENCE_FSPH is the
average value of the sum of squares of high-
pressure-side static pressure uctuations under
normal condition.
As the value of RATIO_FSPH is below the value
of DIAG_LIM [6], EJX gives an alarm of "High Side
Blocking". On the other hand, if this value exceeds
the value of DIAG_LIM [5], EJX gives an alarm of
“Large Fluctuation of High Side”.
 Large Fluctuation Detection
When a pump or compressor starts, the large
uctuation is generated as process condition
changes rapidly. This phenomenon affects process
uctuation measurement, so correct blockage
detection is not performed.
If “Large uctuation of Low Side” or “Large
uctuation of High Side” is detected, consider
whether a blockage result is correct.
The threshold values to detect large uctuation are
set to DIAG_LIM [3] and [5].
Since these values are enough to detect large
uctuation, it is not almost necessary to change
them.