How to Select an Industrial Flow Meter: Coriolis, Electromagnetic and Turbine
Flow measurement is used for process control, mass balance, custody transfer and energy efficiency. The first step is to define the fluid type (liquid, gas or vapor), its conductivity, viscosity, presence of solids and the operating range. With this data viable technologies are shortlisted.
1. Electromagnetic flow meter (magmeter)
The electromagnetic meter applies Faraday's law of induction: a magnetic field generated by coils induces a voltage proportional to the fluid velocity. It only works with conductive liquids (conductivity above approximately 5 µS/cm).
- Advantages: No moving parts, no flow obstruction, high accuracy (±0.2 to ±0.5%), insensitive to density and viscosity, ideal for slurries and abrasive or corrosive liquids with proper linings.
- Limitations: Does not measure gas or vapor, requires conductive liquid, and needs a full pipe section for good measurement.
- Applications: Water, wastewater, slurries, acids, caustic solutions, food industry (with sanitary materials).
MARPATECH represents the Arkon electromagnetic flow meter line, suitable for a wide range of conductive liquids in mining, water treatment and chemical processes.
2. Coriolis mass flow meter
The Coriolis meter simultaneously measures mass and density by exploiting the deformation of a vibrating tube caused by the Coriolis acceleration of the fluid. It is the most accurate technology available for liquids and gases.
- Advantages: Mass and density measurements independent of temperature, pressure, viscosity and flow profile; accuracy of ±0.1% to ±0.2% of reading; no long straight runs required; low uncertainty for custody transfer.
- Limitations: Higher pressure drop (internal restriction), higher cost, sensitive to external vibration and tube filling.
- Applications: High-value gases and liquids, custody transfer, additive dosing, inline density control, tank filling.
MARPATECH represents Brooks Instrument Coriolis mass meters, a world reference in mass flow and custody transfer.
3. Turbine flow meter
The turbine meter uses a rotor spinning at a speed proportional to the fluid velocity, detected by magnetic or photoelectric sensors. It is a mature, economical and fast-responding technology.
- Advantages: Accuracy of ±0.5% to ±1%, wide range (high turndown), fast response, moderate cost, ideal for clean and lubricating fluids.
- Limitations: Moving parts subject to wear and blockage; not suitable for slurries or fluids with solids; sensitive to viscosity fluctuations and pulsating flow.
- Applications: Hydrocarbons, natural gas (with conditioning), clean water, fuels, lubricants.
MARPATECH represents Hoffer Flow Controls turbine meters, widely used in oil and gas, fuels and calibration of other technologies.
4. Variable area meter (rotameter)
The rotameter measures flow by the position of a float inside a conical tube. It is simple, economical and requires no external power, ideal for local indication and purges.
- Advantages: Low cost, no power supply, direct visual reading, useful for instrument purges and local indication.
- Limitations: Low accuracy (±2% to ±4%), requires local reading (not suitable for remote transmission without options), sensitive to vacuum and limited range.
- Applications: Purges, local gas/liquid indication, seal protection, applications where high accuracy is not required.
MARPATECH represents Brooks metal tube variable area meters, used in natural gas, petrochemical and Oil & Gas applications.
5. Comparison criteria
| Criteria | Electromagnetic | Coriolis | Turbine |
|---|---|---|---|
| Typical accuracy | ±0.2–0.5% | ±0.1–0.2% | ±0.5–1% |
| Fluids | Conductive liquids | Liquids and gases | Clean liquids and gas |
| Moving parts | No | No | Yes (rotor) |
| Pressure drop | Low | Medium/high | Low |
| Relative cost | Medium | High | Low/medium |
| Measures density | No | Yes | No |
Conclusion
Choosing a flow meter depends on four factors: the fluid (state, conductivity, cleanliness), required accuracy (control vs custody), cost and installation conditions (straight runs, space, vibration). For moderate-cost conductive liquids, the electromagnetic meter is the most robust option; for gases and high accuracy, Coriolis; for clean and economical fluids, turbine.
MARPATECH SAC represents in Peru, Argentina and Colombia leading flow meter manufacturers including Brooks, Hoffer and Arkon, providing technical advisory to select the most suitable technology for each process.
Frequently asked questions
Because it requires the fluid to be electrically conductive for Faraday's law to generate a measurable signal. Gas and vapor are not conductive, so they do not produce the needed induced voltage.
When high mass accuracy, inline density measurement or custody transfer of high-value fluids is required. Its ability to measure mass and density without depending on other variables justifies the investment.
Electromagnetic and Coriolis meters generally tolerate the lack of straight runs better. Turbines and rotameters usually require 5 to 10 diameters upstream and 3 to 5 downstream to ensure a stable flow profile.