<7. HART Communication>
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IM 01C25W05-01EN
■ High pressure side blockage simulation test
1) Close the valve on the high pressure side.
2) Check that the Pres 1 value is not changing
greatly. If it does, open the valve slightly.
3) Set the Diag Mode parameter to Calculation,
and start the ILBD operation.
4) After the total time specified in the Diag Period
and Diag Supp Count parameters elapses,
check that “Pres 1 Side Blocking” is indicated in
the Diag Error parameter.
5) If the analog output is configured to shift in
response to the alarm occurrence, check also
the behavior of the output.
6) Open the valve fully, and check that the alarm
clears.
■ Low pressure side blockage simulation test
1) Close the valve on the low pressure side.
2) Check that the Pres 2 value is not changing
greatly. If it does, open the valve slightly.
3) Set the Diag Mode parameter to Calculation,
and start the ILBD operation.
4) After the total time specified in the Diag Period
and Diag Supp Count parameters elapses,
check that “Pres 2 Side Blocking” is indicated in
the Diag Error parameter.
5) If the analog output is configured to shift in
response to the alarm occurrence, check also
the behavior of the output.
6) Open the valve fully, and check that the alarm
clears.
■ Both-side blockage simulation test
1) Close all valves.
2) Check that the DP value is not changing greatly.
If it does, open the valve slightly.
3) Set the Diag Mode parameter to Calculation,
and start the ILBD operation.
4) After the total time specified in the Diag Period
and Diag Supp Count parameters elapses,
check that “Pres 1 Side Blocking” and “Pres 2
Side Blocking” are indicated in the Diag Error
parameter.
5) If the analog output is configured to shift in
response to the alarm occurrence, check also
the behavior of the output.
6) Open the valve fully, and check that the alarm
clears.
7.3.2.2.9 ILBD Execution
After checking the conditions and blockage
detection capacity, start the actual blockage
detection operation.
1) Check the sampling period (Diag Period
parameter).
2) Check the setting that specifies how many
times the pressure fluctuation parameter is
to exceed the threshold for an impulse line
blockage to be detected (the Diag Supp Count
parameter). The factory default setting is 3.
3) Set the Diag Mode parameter to Calculation,
and start the ILBD operation.
If reference values have not been acquired, set
the Diag Mode parameter to Reference. After
they are acquired, the transmitter automatically
switches to ILBD operation.
(At the same time, the Diag Mode parameter
also switches to Calculation.)
7.3.2.2.10 Tuning
If not a large enough pressure fluctuation can be
detected or if alarms occur frequently, change
the blockage detection threshold or change the
sampling period in order to increase the blockage
detection accuracy.
To perform tuning, the Diag Mode parameter must
be set to Stop.
■ Changing the threshold
The following figure uses a monochrome bar to
illustrate the effect of tuning.
F0721.ai
0
-1
1
0
1
3
Lower limit threshold
Upper limit threshold
(1)
Lim fDPmin
(2)
Lim fP2min
(3)
Lim fP1min
(1)
Lim fDPmax
(2)
Lim fP2max
(3)
Lim fP1max
a) Ratio fDP…(1), Ratio fP2…(2), Ratio fP1…(3)
b) SQRT (BlkF/Ref BlkF)... (4)
Lower limit threshold
Upper limit threshold
(4)
Lim BlkFmin
(4)
Lim BlkFmax
Figure 7.3.8 Illustration of Threshold Tuning
