YOKOGAWA DPharp EJX***A Series, User Manual

Page: 54 / 98

<4. Diagnostics>
4-7
IM 01C25T01-06EN
Table 4.3 Default Values of Limit Parameter
#
Parameter
Differential pressure
transmitter
Flange
mounted
differential
pressure
transmitter
Diaphragm
sealed differential
pressure/
pressure
transmitter
Absolute
pressure
transmitter
Gauge
pressure
transmitter
Gauge/
Absol ute
pressure
transmitter
EJX110A
EJX115A
EJX130A
EJX120A EJX210A EJX118A
Note 1
EJX438A
EJX310A EJX430A
EJX440A
EJX510A
EJX530A
EJX610A
EJX630A
[1] Lim fDPmax 3 3 10000 10000 10000 10000 10000
[2]
Lim fDPmin
0.3 0.3 0.3 0.3 0.3 0.3 0.3
[3] Lim fSPlmax 5 10000 10000 10000 10000 10000 10000
[4] Lim fSPlmin 0.5 0 0 0 0 0 0
[5]
Lim fSPhmax
5 10000 10000 10000 10000 10000 10000
[6] Lim fSPhmin 0.5 0 0 0 0 0 0
[7] Lim BlkFmax 0.6 10 10 10 10 10 10
[8]
Lim BlkFmin
-0.6 -10 -10 -10 -10 -10 -10
[9]
Lim DPAvgmax
Note 2
1 1 1 1 1 1 1
[10]
Lim DPAvgmin
Note 2
0.05 0.2 -1 -1 0.05 0.05 0.05
Note 1: The default values are set for level measurement. If EJX118A is applied to flow measurement, enter the same value to Limit
parameter [1] to [10] as those of EJX110A.
Note 2: It indicates the threshold value for “ILBD over range” (refer to 4.2.2.5).

H/L 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 fluctuation values, BlkF , is used to
detect it. The value changes within a range of –1
to +1. As BlkF appr1, the high-pressure-
side blockage progresses. On the other hand, if it
approaches –1, the low-pressure-side blockage
progresses.
1
0
1
0
F0404.ai
BlkF
Blockage detection for
high-pressure side
Threshold
Blockage Progress
BlkF
Blockage detection for
low-pressure side
Threshold
Blockage Progress
-1 -1
Figure 4.3 Relation between Blockage Progress
and BlkF
The each threshold value to detect the high- or low-
pressure-side blockage is set to Lim BlkFmax or
Lim BlkFmin
.

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
fluctuation values.
Ratio fDP
, SQRT (
fDP / Ref
fDP ) is used to detect A/B blocking. Ref fDP is the
average value of the sum of squares of differential
pressure fluctuations under normal condition.
As the value of Ratio fDP exceeds the value of
Lim fDPmax
, EJX gives basically an alarm of “A
Blocking”. On the other hand, if this value is below
the value of
Lim fDPmin
, EJX gives an alarm of “B
Blocking.
As a high- or low-pressure-side blockage
progresses,
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,
fDP
decreases.
Therefore, “B Blocking” with a differential pressure
transmitter indicates that both-side impulse lines
are plugged.
NOTE
A single-side impulse line blockage may
generate “B blocking” under the condition where
the fluctuation amplitude is much different
between high- and low-pressure sides.