Yokogawa EJX930A - Manual (Page 156)

<Appendix 8. Advanced Diagnostics>
A8-12
IM 01C25T02-01E
3) Set “Calculation” to DIAG_MODE so as to start
blockage detection operation.
4) Check that an alarm of “High Side Blocking” is
generated after the time that consists of DIAG_
PERIOD and DIAG_COUNT passed.
5) Check also the operation of the analog alert if
an analog alert is set.
6) Open the valve completely and check that there
are no alarms.
 Simulation of Low-pressure-side
Blockage
1) Close the low-pressure-side valve.
2) Confirm the value of PRIMARY_VALUE is
stable. If unstable, open valve a little.
3) Set “Calculation” to DIAG_MODE so as to start
blockage detection operation.
4) Check that an alarm of “Low Side Blocking” is
generated after the time that consists of DIAG_
PERIOD and DIAG_COUNT passed.
5) Check also the operation of the analog alert if
an analog alert is set.
6) Open the valve completely and check that there
are no alarms.
 Simulation of Both-pressure-side
Blockage
1) Close the both-pressure-side valves.
2) Confirm the value of PRIMARY_VALUE is
stable. If unstable, open valve a little.
3) Set “Calculation” to DIAG_MODE so as to start
blockage detection operation.
4) Check that an alarm of “B Blocking” is
generated after the time that consists of DIAG_
PERIOD and DIAG_COUNT passed.
5) Check also the operation of the analog alert if
an analog alert is set.
6) Open the valves completely and check that
there are no alarms.
A8.2.9 Start ILBD Operation
If process condition and capability to detect a
blockage are confirmed, the ILBD operation can be
started according to the following procedure.
1) Check the value of sampling period
(DIAG_PERIOD).
2) Check the number of times that detect the
blockage consecutively in order to give an
alarm (DIAG_COUNT). The default value at the
shipment is set to 3 times.
3) Set “Calculation” status to DIAG_MODE.
If the reference value has not yet been
obtained, set “Reference” to DIAG_MODE.
After obtained the reference values, the ILBD
starts automatically. At the same time, DIAG_
MODE changes automatically from “Reference”
to “Calculation”.
A8.2.10 Tuning
When the pressure fluctuation amplitude in fluids is
not sufficiently large or an alarm is often generated
according to the process condition, tune up by
changing the threshold for the blockage detection
(DIAG_LIM) or the sampling period (DIAG_
PERIOD) to enhance the accuracy of the blockage
detection.
The ILBD operation must be stopped to tune up.
Set “Stop” to DIAG_MODE.
A8.2.10.1 Threshold Value
The figure below shows the image of tuning effect
with a monochrome bar.
FA0809.ai
0 1 3
Threshold (lower side) Threshold (upper side)
1) DIAG_LIM [2]
2) DIAG_LIM [4]
3) DIAG_LIM [6]
1) DIAG_LIM [1]
2) DIAG_LIM [3]
3) DIAG_LIM [5]
(a) The tuning image of the threshold values for
1) RATIO_FDP Sqrt
(VALUE_FDP/REFERENCE_FDP),
2) RATIO_FSPL Sqrt
(VALUE_FSPL/REFERENCE_FSPL),
3) RATIO_FSPH Sqrt
(VALUE_FSPH/REFERENCE_FSPH)
(b) The tuning image of the threshold values for
4) Sqrt (VALUE_BLKF/REFERENCE_BLKF)
0 -1 1
Threshold (lower side) Threshold (upper side)
4) DIAG_LIM [8] 4) DIAG_LIM [7]
Figure A8.7 Tuning Image of Threshold Value