Manual

<Appendix 8. Advanced Diagnostics>
A8-3
IM 01C25R03-01E
A8.2.1 Blockage Detection
 DIAG_LIM
When the parameter based on pressure uctuation
exceeds the preset value, EJX diagnoses an
impulse line as blockage and gives an alarm. The
threshold values are set to DIAG_LIM [1] to [10] in
the SENSOR Transducer block.
TableA8.2 shows the default values at the factory
setting, which are different according to the model.
NOTE
When ILBD is performed for the rst time, use
the default value. If the pressure uctuation
amplitude is low or a false alarm is often
generated after ILBD is performed, change the
values of DIAG_LIM according to the procedure
described in A8.2.10.
DIAG_LIM
# Parameter Threshold value
[1] fdpmax Threshold to detect “A Blocking” by
using RATIO_FDP
[2] fdpmin Threshold to detect “B Blocking” by
using RATIO_FDP
[3] fsplmax Threshold to detect “Large
Fluctuation of Low Side” by using
RATIO_FSPL
[4] fsplmin Threshold to detect “Low Side
Blocking” by using RATIO_FSPL
[5] fsphmax Threshold to detect “Large
Fluctuation of High Side” by using
RATIO_FSPH
[6] fsphmin Threshold to detect “High Side
Blocking” by using RATIO_FSPH
[7] blkfmax Threshold to detect “High Side
Blocking” by using VALUE_BLKF
[8] blkfmin Threshold to detect “Low Side
Blocking” by using VALUE_BLKF
[9] dpavgmax Threshold to detect “Outside
Diagosis Range” by using VALUE_
DPAVG and to detect “Invalid
Ref xx” by using REFERENCE_
DPAVG.
[10] dpavgmin Threshold to detect “Outside
Diagosis Range” by using VALUE_
DPAVG and to detect “Invalid
Ref xx” by using REFERENCE_
DPAVG.
Table A8.2 Default Values of DIAG_LIM
#
Parameter
Multivariable transmitter
EJX910A / EJX930A
[1] fdpmax 3
[2] fdpmin 0.3
[3] fsplmax 5
[4] fsplmin 0.5
[5] fsphmax 5
[6] fsphmin 0.5
[7] blkfmax 0.6
[8] blkfmin -0.6
[9] dpavgmax
*1
1
[10] dpavgmin
*1
0.05
*1: It indicates the threshold value for “Outside Diagnosis
Range” (refer to A8.2.5).
 A/B Blocking Detection
“A Blocking” and “B Blocking” indicates the result
estimated from blockage degree based on the
difference of the high- and low-pressure-side
uctuation values. RATIO_FDP, SQRT (VALUE_
FDP / REFERENCE_FDP) is used to detect A/B
Blocking.
REFERENCE_FDP is the average value of the sum
of squares of differential pressure uctuations under
normal condition. As the value of RATIO_FDP
exceeds the value of DIAG_LIM [1], EJX gives
basically an alarm of “A Blocking”. On the other
hand, if this value is below the value of DIAG_LIM
[2], EJX gives an alarm of “B Blocking. As a high- or
low-pressure-side blockage progresses, VALUE_
FDP increases. Therefore, “A Blocking” with a
differential pressure transmitter indicates that a
single-side impulse line is plugged for a differential
pressure transmitter.
As the both-side blockages progress
simultaneously, VALUE_FDP decreases.
Therefore, “B Blocking” with a differential pressure
transmitter indicates that bothside impulse lines are
plugged.
NOTE
A single-side impulse line blockage may
generate “B blocking” under the condition where
the uctuation amplitude is much different
between high- and low-pressure sides.
With a transmitter to measure pressure or tank
level, “B Blocking” only is detected.