Coriolis flow meters provide accuracy and reliability for measuring mass flow, density and temperature of liquids and gases and are used in the oil and gas, chemical processing, food and beverage and pharmaceutical industries.
Coriolis flow meters give a direct measurement of mass flow, tend to exhibit lower sensitivity to fluid properties and other mutable circumstances, and used in almost every application.
These meters are generally reliable and have Coriolis flow meter have many advantages, but sometimes operational problems can affect how well they work.
Knowledge of applicable operational issues and solution, is valuable for continued operation, reduced downtime, ensure appropriate measurements at all times. This article features valuable tips and solution suggestions for applicable common operating issues associated with Coriolis flow meters.
1. Measurement Inaccuracy in Coriolis Flow Meters.
While Coriolis flow meters are very accurate, they can have issues from various causes.
Typical causes:
- Incorrect installation of the meter: they should always be lined up within ±1° of the specified orientation otherwise it can cause zero drift.
- Vibration or pulsating flow: if there is vibration greater than 2 g outside of the sensor or any flow pulsation greater than 10%, the sensor may not read correctly.
- Fluid properties: Temporary measurement errors can happen with fluids that are extremely viscous (up to 10,000 cP) or fluids that have a gas content of 5 – 10%.
- Old sensors or dirt: if there is dirt in the flow tubes thick enough (>0.2 mm) then the accuracy will drop by ±0.5% of the reading.
Recommended solutions:
- Confirm the installation, pipe support, and orientation are correct or if the flow is unstable, vibration isolators and/or pulsation dampeners.
- Confirm the zero reading and calibrate flow meter at regular intervals.
- Inspect flow tubes and clean them or replace if contamination is greater than 0.1 mm.
Practical Tip: A properly calibrated Coriolis meter will usually maintain its accuracy to ±0.1 –0.2% of the mass flow rate. An example configuration used fixed support + flexible pipeline to minimize vibration.
2. Zero Drift.
Zero drift occurs when the meter shows a flow that isn’t zero, but not fluid is passing through. Zero drift can cause errors in process or batching.
Common Causes:
- Variations in temperature: Rapid temperature changes (±20 °C within minutes) can result in deformation of the flow tubes.
- Mechanical stress: Should pipes not be properly aligned, or otherwise supported, and bend more than ±2 mm then the sensor may be distorted.
- Electrical interference: Nearby equipment with electrical potential within the monitoring phase (10–50 kV/m EMI) can change the zero point.
Solutions Recommended:
Complete regular zero-point checks, especially after maintenance or a temperature differential. Below video gives you direction and instructions on zero point calibration on SH-CMF series Coriolis flow meters.
- Ensure the pipes are aligned correctly and securely fastened.
- Protect signal cables from electrical noise; clean the electrical noise if needed.
Case Example: A chemical plant had a continuous reading of zero drift because there were uninsulated hot water lines in the vicinity of the meter. It fixed the issue by restraining and insulating the hot water lines.
3. Excessive Vibration or Noise:
Excessive vibration or noise will reduce the life of the Coriolis meter and cause inconsistent indications.
Common causes:
- Flow turbulence from the process: disturbances in the upstream greater than 1–2 meters per second will create vibration.
- An installation that is not secured: a meter that is not securely mounted will contribute to resonance.
- Cavitation or entrained air: If the gas content exceeds 3% or there is cavitation, readings will be errant.
Solutions recommended:
- Install flow straighteners upstream to stabilize the flow.
- Affix the meter well, reducing the opportunity for mechanical resonance.
- Degas the fluid medium or alter the operating conditions to prevent cavitation.
Additional useful tips: Use flexible connectors and damping supports will minimize vibration and allow on-tolerance readings of ±0.2% in high pressure (up to 40 bar) systems.
4. Connectivity and Signal Problems.
Digital Coriolis meters communicate through electronic signals. Connectivity issues could lead to erratic readings or total loss of signal.
Common Causes:
- Loosely connected wires and connectors or unnecessary corrosion.
- Power supply differences of +/− 10% for voltage can lead to other variations to the electronics.
- Old or outdated firmware can lead to erratic failures.
Remedies:
- Check each of the electrical connections for a tight connection and replace broken cables.
- Use regulated 24 VDC power supply.
- Update firmware based on manufacturer’s instructions.
NOTE: Most newer meters have diagnostic alarms that can pinpoint signal errors before they effect the process.
5. Errors in Density and Temperature Measurement.
- Multi-parameters are measured and displayed by Coriolis flow meter
- Coriolis meters also measure fluid density and temperature, which are critical temporary density measurement errors.
Common Causes:
- Thermal lag: Very rapid change of ±15°C/ <5minutes will affect the displayed readings.
- Fouling inside tubes: If the inside tube is fouled with deposits greater than 0.2 mm, density measurement errors may occur.
- Operating beyond the limits: the operational limits of most meters are 0 – 120°C; 0 – 40 bar.
Solutions Recommended:
- Let the Coriolis meter stabilizes after a temperature change.
- Clean the tubes frequently to avoid fouling.
- Ensure that operational conditions remain within the specified limits.
Example: In a dairy processing application, an increased fat content in the milk can cause the inside tube to slightly foul. A routine cleaning of the meter will keep the density error within ±0.1 kg/m³.
6. Summary Table of Common Issues
| Issue | Common Causes | Recommended Solutions | Reference Data / Typical Values |
| Measurement Inaccuracy | Improper installation; pulsating flow; high viscosity or gas content; sensor aging | Verify installation; use dampeners; regular calibration; clean/replace tubes | Accuracy: ±0.1–0.2% mass flow; Fluid viscosity up to 10,000 cP; Gas content <5% |
| Zero Drift | Temperature fluctuations; mechanical stress; electrical interference | Regular zero-point checks; secure mounting; shield cables | Temperature change: ±20°C; Pipe deflection: <±2 mm |
| Excessive Vibration / Noise | Process turbulence; loose installation; cavitation or air bubbles | Install flow straighteners; secure meter; degas liquid | Turbulence: <1–2 m/s; Pressure: up to 40 bar; Vibration <2 g |
| Connectivity / Signal Issues | Loose/corroded wiring; voltage fluctuations; outdated firmware | Tighten/replace wiring; use regulated power supply; update firmware | Power supply: 24 VDC ±10%; EMI shielding recommended |
| Density / Temperature Errors | Thermal lag; tube fouling; operating beyond meter limits | Allow stabilization; clean tubes; stay within specified range | Temperature: 0–120°C; Pressure: 0–40 bar; Density error <±0.1 kg/m³ |
7. Common Questions About Coriolis Flow Meters.
Q1: How often should you calibrate the Coriolis flow meter?
A: Every 6-12 months for critical services. Zero should be checked after maintenance or change to your process.
Q2: Can Coriolis meters measure highly viscous fluids?
A: Yes, they measure up to 100,000 cP, but you will need to clean the meter more often with a very thick fluid to maintain precision.
Q3: What causes zero drift?
A: Drift is largely caused by a change in temperature, mechanical stress, and electrical noise. Drift can be managed by installing the meter cleanly and correctly, properly supporting the piping, and shielding the meter from EMI.
Q4: How do I reduce vibration issues?
A: You can reduce the effects of vibration by using flow straighteners, making sure the meter is secured properly, and introducing flexible connections or damping supports.
Q5: Are Coriolis meters affected by aerated or bubbly liquids?
A: Yes, aerated gas can be trapped in the meter or cause cavitation and affect measurement. By degassing the product or the use of flow conditioning you can maintain ±0.2% accuracies.
Q6: What service conditions affect the accuracy of the meter?
A: Extreme conditions of temperature, vibration, or strong electromagnetic fields. Ensure the meter is within conditions of 0-120°C, for pressure of 0-40 bar, and shielded from EMI.
8. Some Other Maintenance Considerations.
Monitor trends: The meter’s diagnostic features will allow you to track the trends of flow, density, and temperature over time.
Implement cleaning protocols: When utilizing the sensor for food, dairy, or other chemical processes, proper cleaning of the tubes should be performed to help prevent fouling.
Document changes to correlate with performance: Remember to document any calibrations, maintenance, or changes in the process to relate back to how the meter is performing.
Final Thoughts
Coriolis flow meters are very accurate and reliable, but must be able to be installed, maintained, and troubleshot properly to achieve maximum utilization. With these solutions, you can minimize solving any routine issues of incorrect measurements, zero drift, vibration and connectivity problems, and density or temperature errors.
As a result, daily operators using diligence will maintain their mass flow accuracy to ±0.1 – 0.2% by simply performing operational maintenance, calibrating, and monitoring performance measuring. All of this will also promote longer life of the meter plus reliable operations in the industry.
All in all, Coriolis meters will remain a steady measurement solution in measuring mass flow accurately in a diverse industrial base of industries.