YOKOGAWA DPharp EJXC40A, Руководство пользователя

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<7. HART Communication>
7-42
IM 01C25W05-01EN
7.3.2.2.7 Reference Value Acquisition
When the impulse line is blocked, the pressure
fluctuation value decreases. To detect this change,
a pressure fluctuation that can be used as a
reference for the damping rate is necessary.
IMPORTANT
• If blockage has already progressed when the
reference value is acquired, blockage cannot
be detected correctly. Clean the impulse line
before acquiring the reference value.
• If liquid is filled in the impulse line, check that
there are no bubbles or the like in the liquid.
• Acquire the reference under steady state
operating conditions.
■ Starting to sample
The reference value is acquired over 180 seconds,
a default value set in the Diag Period parameter.
1) Check that the sampling period (Diag Period
parameter) is set to 180 seconds.
2) Set the Diag Mode parameter to Reference
(start the reference value acquisition
immediately after it is set).
IMPORTANT
• A reference value is acquired for each
ILBD detection parameter. If the Diag Mode
parameter is set to Reference again, new
reference values are acquired overwriting
the previous reference values.
• If the transmitter turns off when the Diag
Mode parameter is set to Reference, ILBD
will be in a stopped state when the power
returns (the Diag Mode is set to Stop). Set
Diag Mode to Reference, and acquire the
reference values again.
■ Ending sampling
After 180 seconds, the acquisition of the reference
values automatically ends, and the Diag Mode
parameter switches automatically from Reference
to Calculation.
Check that the sampling has finished by confirming
that the Diag Mode has changed to Calculation.
■ Checking the reference values
The latest reference values are stored in the
following parameters.
• Ref fDP
• Ref fP2
• Ref fP1
• Ref BlkF
• Ref DPAvg
• Recalling parameters
Recall
parameters
[Root menu] → Diag/Service → Diag
Parameters → ILBD parameters →
Status → Diag Reference → Ref fDP/
Ref fP2/Ref fP1/Ref BlkF/Ref DPAvg
After sampling is finished, check that the values
have been updated.
■ Checking invalid reference values
If pressure fluctuation used as the reference cannot
be acquired, an alarm occurs for the relevant
pressure fluctuation parameters, and a portion of
ILBD is not executed.
Check that such alarms (Invalid Ref xx) are not
indicated in the Diag Error parameter.
If such alarms have occurred, review the process
conditions once again, and reacquire the reference
values.
CAUTION
Even when such alarms occur, the Diag Mode
parameter will be set to Calculation, but ILBD will
not be executed.
7.3.2.2.8 Checking the Blockage Detection
Operating Capacity
Before executing an actual ILBD operation, check
the blockage detection capacity by using a valve.
Check that when a blockage is created artificially by
closing the valve, an alarm occurs.
CAUTION
In pressure measurement or liquid level
measurement, if one side is released to the
atmosphere and there is hardly any pressure
fluctuation, close the valve on the other side
(high pressure side or low pressure side) to
perform a blockage detection simulation test.