YOKOGAWA DPharp EJXC40A, Руководство пользователя

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<7. HART Communication>
7-33
IM 01C25W05-01EN
7.3.2.2.1 Blockage Determination
■ Limit parameter
When a parameter based on pressure fluctuation
exceeds a preset threshold, a blockage is assumed
to have occurred in the transmitter, and an alarm
is generated. The threshold used for determination
is set in the Limit parameter shown in the following
table.
Limit parameter
# Parameter Threshold value
[1] Lim fDPmax Threshold for detecting “A
Blocking” using Ratio fDP.
[2] Lim fDPmin Threshold for detecting “B
Blocking” using Ratio fDP.
[3] Lim fP2max Threshold for detecting “ Large
Fluct Pres 2” using Ratio fP2
[4] Lim fP2min Threshold for detecting “Pres 2
Side Blocking” using Ratio fP2.
[5] Lim fP1max Threshold for detecting “ Large
Fluct Pres 1” using Ratio fP1.
[6] Lim fP1min Threshold for detecting “Pres 1
Side Blocking” using Ratio fP1.
[7] Lim BlkFmax Threshold for detecting “Pres 1
Side Blocking” using BlkF.
[8] Lim BlkFmin Threshold for detecting “Pres 2
Side Blocking” using BlkF.
[9] Lim DPAvgmax Threshold for detection “ILDB
over Range” using DPAvg and
“Invalid Ref DP” using Ref
DPAvg.
[10] Lim DPAvgmin Threshold for detection “ILDB
over Range” using DPAvg and
“Invalid Ref DP” using Ref
DPAvg.
Table 7.3.2 shows the factory default values.
Table 7.3.2 Factory Default Limit Parameter Value
# Parameter Value
[1] Lim fDPmax 3.00
[2] Lim fDPmin 0.30
[3] Lim fP2max 3.00
[4] Lim fP2min 0.30
[5] Lim fP1max 3.00
[6] Lim fP1min 0.30
[7] Lim BlkFmax 0.60
[8] Lim BlkFmin −0.60
[9] Lim DPAvgmax 1.00
[10] Lim DPAvgmin −1.00
CAUTION
If you are using this for the first time, use the
default values. If not enough pressure fluctuation
can be detected in valve simulation tests or in
actual operation or if alarms occur frequently,
refer to subsection 7.3.2.2.10, “Tuning,” and
change the Limit parameter, which will be used
as the threshold.
■ Determination of A Blocking and B Blocking
A Blocking and B Blocking are blockage detection
results determined by the blockage level based on
the difference in the pressure fluctuation between
the high pressure side and low pressure side.
Ratio fDP, which is the square root of fDP relative
to SQRT (fDP / Ref fDP), is used to determine
blockage.
Ref fDP is an average of the sum of squares of the
differential pressure fluctuation acquired during
steady state operation. It is a reference value used
in the comparison with the value obtained during
diagnostic execution (fDP).
If Ratio fDP exceeds the Lim fDPmax value, “A
Blocking” is detected. If it falls below the Lim
fDPmin value, “B Blocking” is detected.
If blockage progresses both in the high pressure
side and low pressure side simultaneously in a
digital remote sensor transmitter, fDP decreases.
If blockage occurs in both sides, “B Blocking” is
detected.
If blockage progresses in the impulse line on high
pressure side or low pressure side, “A Blocking” or
“B Blocking” is detected.
CAUTION
In a condition in which the difference in the
pressure fluctuation between the high pressure
side and low pressure side becomes extremely
large, a blockage in the impulse line on one side
may be detected as “B Blocking.”
Note that if the transmitter is used for pressure
measurement or liquid level measurement, only “B
Blocking” detection is performed.