Yokogawa EJX440A - Manual (Page 47)

<4. Diagnostics>
4-7
IM 01C25T01-01E
4.2.2.3 Operation Parameters
 Diag Mode
Diag Mode gives the directive for the ILBD
operation. There are following three modes.
Diag Mode
Index Mode Function
0 Stop The blockage detection operation
is stopped.
1 Calculation The blockage detection operation
is performed.
Alarms are generated along with
the result.
2 Reference Reference values for the
blockage detection are obtained
and updated to the latest. After
sampling reference values, this
mode changes to "Calculation".
When the blockage detection operation is
performed, set “Calculation” to Diag Mode. “Stop”
must be set when you change a threshold value or
set an alarm. “Reference” is set in order to obtain
the reference fluctuation values under the normal
configuration.
 Diag Period
The values such as Ratio fDP and BlkF are
averaged based on several hundreds of pressure
fluctuation values in constant time. Diag Period
defines the sampling time is. The default value at
the shipment is set to 180 seconds.
For the information on how to change the sampling
period, refer to 4.2.2.10.
 Diag Supp Count
When the value as Ratio fDP or BlkF exceeds
the threshold value for several times in a row,
it is estimated that the impulse line is plugged.
Diag Supp Count defines the number of times to
estimate blockage detection.
If
Diag Supp Count is set to three times, an
alarm is not generated at part ‘A’ in Figure 4.2.3.
Because the first and second values only exceeded
consecutively the threshold.
When the value exceeds consecutively the
threshold value three times, an alarm is generated
(see part ‘B’ in Figure 4.2.3).
B A
B A
F0408.ai
Diag Supp Count (Number of times: 3)
Diag Supp Count (Number of times: 3)
Diag Period
Diag Period
Upper Threshold
(Ex. Lim fDPmax)
Upper Threshold
(Ex. Lim fDPmin)
An alarm is generated.
An alarm is generated.
Time
Time
Figure 4.2.3 Relationship of Diag Supp Count and
Alarm
The number of detection to give an alarm is set for
each blockage detection function. The default value
at the shipment is set to three times.
If fluctuating around the threshold value, an alarm
may be often generated. In this case, change the
threshold value (Limit parameter) or the sampling
time ( Diag Period) to enhance the accuracy of the
blockage detection. Refer to 4.2.2.10.