Red Seal Measurement Datamate 2200, Руководство по эксплуатации и техническому обслуживанию

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Datamate 2200 O&M
Page 48
8.7 Slug Flow Inhibit
The flow meter will resume normal operation when the density measurement level is
above the low density cutoff value and below the high density cutoff value. The slug flow
inhibit feature is intended to detect process changes due to density that may affect the
meter operation. This feature works by monitoring the process density. When the process
density goes above or below the slug flow setpoints, the mass rate defaults to the
programmed fallback value. As recommended in the Mass Flow Installation Guide
(M600), R
ed
S
eal Measurement
recommends process piping that prevents large air slugs
from mixing with the process liquid. However, if this is unavoidable, the effects of air slugs
may be minimized using the Slug Inhibit software feature. The software feature works by
looking for an increase or decrease in measured density. An increase or decrease in
measured density occurs when air or gas becomes mixed with the process fluid. When
the concentrations of gas become significant, air slugs develop and cause the indicated
flow rate to fluctuate erratically. When the process density moves above or below the
setpoints, the software feature causes the Datamate 2200 transmitter to ignore the erratic
flow signal and
to substitute it with a fallback value. This fallback value is based on the programmed
fallback values for mass and volume flow (See Section 9.6.5). Typically fallback values
are selected to either lock into the last measured mass or volume flow rate prior to the
increase or decrease in density, OR drop the flow rate to zero. Consequently, whenever
the software feature is engaged, an active measurement of the flow in the tubes is no
longer in effect .
A slug flow condition causes the following to occur
:
8.8 Transmitter Power Failure
If the Datamate 2200 transmitter power fails, the following will occur:
• transmitter pulse outputs will go to 0 Hz
• transmitter 4-20mA outputs will go to 0mA
If the Datamate 2200 fails as a result of a “Tube Not Vibrating” or “Sensor Error,” the
following will occur:
• transmitter pulse outputs will go to the fallback value
• transmitter 4-20mA outputs will go to the fallback value
NOTE: If the remote system requires a fallback value lower or higher than the respective
4-20mA output signal, set the fallback (positive or negative) to a value at least 12.5%
lower or higher than the 4-20mA span. This will drive the current output to a minimum
value of 2mA or a maximum value of 22mA. (Example: If your 4-20mA flow range
represents 0 to 1000 lbs/min, then by setting the fallback to a value greater than 1125 or
less than -125, the analog output will be driven to 22mA or 2mA respectively.
•
pulse output will hold at the fallback value frequency
•
4-20mA output will hold at the fallback current