Emerson Micro Motion LNG Series, Configuration And Use Manual

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- Do not terminate the shielding inside the wiring compartment.
- 360-degree termination of shielding is unnecessary.
• Eliminate the RFI source.
10.9 Check for two-phase flow (slug flow)
Two-phase flow can cause rapid changes in the drive gain. This can cause a variety of
measurement issues.
1.
Check for two-phase flow alerts (e.g., A105).
If the transmitter is not generating two-phase flow alerts, two-phase flow is not the
source of your problem.
2. Check the process for cavitation, flashing, or leaks.
3. Monitor the density of your process fluid output under normal process conditions.
4. Check the settings of
Two-Phase Flow Low Limit
,
Two-Phase Flow High Limit
, and
Two-Phase
Flow Timeout
.
Tip
You can reduce the occurrence of two-phase flow alerts by setting Two-Phase Flow Low Limit to a
lower value,
Two-Phase Flow High Limit
to a higher value, or
Two-Phase Flow Timeout
to a higher
value.
10.10 Check the drive gain
Excessive or erratic drive gain may indicate any of a variety of process conditions or sensor
problems.
To know whether your drive gain is excessive or erratic, you must collect drive gain data
during the problem condition and compare it to drive gain data from a period of normal
operation.
Excessive (saturated) drive gain
Possible causes and recommended actions for excessive (saturated)
drive gain Table 10-5:
Possible cause Recommended actions
Sensor tubes not completely
full Correct process conditions so that the sensor tubes are full.
Plugged sensor tube Check the pickoff voltages (see Section 10.11 ). If either of them
are close to zero (but neither is zero), plugged tubes may be the
source of your problem. Purge the tubes. In extreme cases, you
may need to replace the sensor.
Drive board or module failure Contact Micro Motion.
Troubleshooting
80 Micro Motion ® LNG Series Meters