YOKOGAWA DPharp EJXC40A, Руководство пользователя

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<7. HART Communication>
7-31
IM 01C25W05-01EN
7.3.2.2 Impulse Line Blockage Detection
Impulse Line Blockage Detection (ILBD) is
performed by statistically processing the measured
values of pressure fluctuation existing in the fluid.
The diagnostic results (blockage occurrences)
can be confirmed with the alarm indications on the
LCD or with analog alerts. For differential pressure
transmitters, the measurement of three signals
(differential pressure, high pressure side pressure,
and low pressure side pressure) enables the
determination of which side, high pressure side or
low pressure side, the blockage is occurring. The
blockage detection results are displayed using the
following four types of messages.
Digital remote sensor transmitter is shipped with
its module 1 side transmitter for high pressure side
measurement and it module 2 side transmitter
for low pressure side measurement. Please read
“high pressure” as “module 1 side”, and “low
pressure side” as “module 2 side” in the following
explanations.
(1) A Blocking, B Blocking
The blockage detection result determined by the
fluctuation in the differential pressure or pressure. A
Blocking and B Blocking is used to indicate whether
the impulse line on one side or on both sides has
been blocked.
NOTE
A blocking is not used on the digital remote
sensor.
(2) Pres 2 Side Blocking
The blockage detection result of the module 2 side
determined by the fluctuation in the BlkF* values or
module 2 side fluctuation.
(3) Pres 1 Side Blocking
The blockage detection result of the module 1 side
determined by the fluctuation in the BlkF* values or
module 1 side fluctuation.
*: The blockage level obtained by statistically comparing
the pressure fluctuation between the module 1 side and
module 2 side. For details, see subsection 7.3.2.2.1.
IMPORTANT
• The basic element of impulse line blockage
detection is the monitoring of fluctuation.
If sufficient fluctuation needed for
determination cannot be obtained, blockage
detection does not work properly.
• If not enough fluctuation is detected when
reference data is acquired, the reference will
be invalid, and blockage detection will not be
executed.
• After fluctuation monitoring is started,
fluctuation may decrease due to factors
other than blockage depending on the
plant operating conditions. If this occurs, an
alarm may be generated on the assumption
that impulse line blockage has occurred.
Determine the validity of the blockage
detection result by taking the plant operating
conditions into consideration.
■ Notes on pressure measurements and liquid
level measurements
In pressure measurements and level
measurements, fluctuation may decrease
particularly in the following cases.
Determine the validity of the blockage detection
result by taking the plant operating conditions into
consideration.
● Pressure measurement
• In pressure measurement, if the pressure
goes outside the ILBD diagnostic range.
• If the flow rate decreases relative to the rate
that was present at the time the reference
data was acquired even when the pressure
remains constant
• If the pressure fluctuation source (pump,
compressor, blower, etc.) stops
● Liquid level measurement
• If the liquid inflow or outflow from the tank
stops
• If the agitator inside the tank stops
• If the pressure fluctuation source (e.g.,
compressor) that controls the inner pressure
of the closed tank stops