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10.8 Density measurement problems
Density measurement problems and recommended actionsTable 10-3:
Problem Possible causes Recommended actions
Erratic density reading • Normal process noise
• Two-phase flow
• Flow rate too high
• Deposition on the tines
• Contaminants or suspended solids in the
process fluid
• Vibration in the pipeline
• Erosion or corrosion
• Check your process conditions.
• Increase the density damping value.
• Reduce the flow rate.
• Check for two-phase flow. See
Section 10.22.
• Ensure that line pressure or sample pres-
sure meets installation requirements.
• Increase back pressure to minimize bubble
formation.
• Clean the tines.
• Minimize vibration in the pipeline.
• Install a flow control method (bypass, flow
chamber, expander, etc.).
• Perform Known Density Verification.
Inaccurate density
reading
• Inaccurate temperature measurement
• Incorrect calibration factors
• Deposition on the tines
• Boundary effect (incorrect installation)
• Verify the temperature reading from the
RTD (on-board temperature sensor).
• Verify the temperature reading from the
external temperature device, if applicable.
• Verify or adjust the density offset and/or
the density meter factor.
• Clean the tines.
• Increase the flow rate.
• Install a thermal insulation jacket.
• Verify the calibration factors.
• Perform Known Density Verification.
• Change the location of the fork.
Density reading too
high
• Deposition on the tines • Clean the tines.
Density reading too
low
• Leaks in the pipework or fittings
• Two-phase flow
• Check for two-phase flow. See
Section 10.22.
Cyclic inaccuracy in
density reading
• Stirrer rotation rate too high
• Tank flow rate too high
• Fork in poor location
• Stirrer creating bubbles
• Solids in tank
• Reduce the stirrer rotation rate.
• Reduce the tank flow rate.
• Move the fork to a location with a lower
flow profile.
• Install a sample bypass.
• Replace the device with a CDM.
Density reading from
device does not
match laboratory val-
ue
• Incorrect calibration factors
• Laboratory conditions do not match sam-
ple conditions
• Verify the calibration factors.
• Verify or adjust the density offset and/or
the density meter factor.
• Ensure that the two fluids are being com-
pared at the same temperature.
Troubleshooting
174 Micro Motion
®
Fork Viscosity Meters (FVM)