Yokogawa EJX115A - Manual (Page 54)

<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 approaches +1, 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.