Yokogawa EJX930A - Manual (Page 150)

<Appendix 8. Advanced Diagnostics>
A8-6
IM 01C25T02-01E
A8.2.3 Operating Parameters
 DIAG_MODE
DIAG_MODE gives the directive for the ILBD
operation. There are following three modes.
DIAG MODE
Code 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. The default value at the
shipment is set to 180 seconds.
For the information on how to change the sampling
period, refer to A8.2.10.
 DIAG_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_
COUNT defines the number of times to estimate
blockage detection.
If DIAG_COUNT is set to three times, an alarm is
not generated at part ‘A’ in Figure A8.3. The reason
is that only the first and second values exceeded
consecutively the threshold.
When the value exceeds consecutively the
threshold value three times, an alarm is generated
(see part ‘B’ in Figure A8.3).
B A
B A
FA0804.ai
DIAG_COUNT(Number of times: 3)
DIAG_COUNT(Number of times: 3)
DIAG_PERIOD
DIAG_PERIOD
Upper Threshold(DIAG_LIM)
Lower Threshold(DIAG_LIM)
An alarm is generated.
An alarm is generated.
Time
Time
Figure A8.3 Relationship of DIAG_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 (DIAG_LIM) or the sampling time
(DIAG_PERIOD) to enhance the accuracy of the
blockage detection. Refer to A8.2.10.