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An Overview of Mass Flow Meters: Types, Operating Principles & Key Technical Specifications
Time：
2025-05-27
Mass flow meters measure the mass rate of flow (kg/h, lb/min, etc.) of liquids or gases directly, eliminating the need to correct for changing temperature or pressure. Below is a concise guide to the main technologies in use today and the specifications that matter when you are selecting one.
1. Major Types and Their Principles
| Type | Core Principle | Typical Media | Strengths | Common Limits |
| Coriolis | In a vibrating U- or Ω-shaped tube, fluid mass flow induces a phase shift (Coriolis force) proportional to mass rate. | Liquids, slurries, gases | Direct mass measurement, high accuracy (±0.05 % of rate), density/temperature output | Cost, pressure drop, line size ≤ DN300 typical |
| Thermal (Constant-T or Constant-Power) | Heat is added to the flow; mass flow is proportional to required heating power (or ΔT) because heat transfer depends on mass velocity & specific heat. | Clean gases (compressed air, N₂, natural gas) & low-viscosity liquids | Wide turndown (100 : 1), low pressure loss, inexpensive | Sensitive to media composition & moisture, needs calibration gas match |
| Differential Pressure with Flow Conditioner (DP-Mass) | Classical DP element (orifice, Venturi) + temperature & pressure sensors; mass derived via equation of state. | Steam, gas, liquids | Uses existing DP taps, high-temperature service | Indirect mass, lower accuracy (±0.5–1 %), requires density comp. |
| Single-Jet or Rotary Piston Positive Displacement | Captures discrete, known volumes; counts cycles to determine mass after density correction. | Custody transfer liquids (fuel oils, LPG) | High accuracy at low flow, independent of viscosity | Pulsating flow, mechanical wear, periodic proving needed |
| Turbine with Density Comp. | Velocity proportional to volumetric flow; mass = volumetric × density via separate sensor. | Clean, low-viscosity liquids | Very low uncertainty (±0.15 %) when calibrated | Requires steady, filtered flow; density errors propagate |
2. Key Technical Specifications
| Specification | What It Tells You | Good Practice / Typical Values |
| Accuracy (System Uncertainty) | Deviation ±% of reading or full scale; dictates fiscal/custody-transfer suitability. | Coriolis 0.05 – 0.2 %, Thermal 1 %, DP-Mass 0.5–1 % |
| Repeatability | Ability to produce the same reading under identical conditions — critical for batching. | Usually ≤ 1/3 of stated accuracy |
| Turndown Ratio | Range over which stated accuracy is maintained. | Coriolis 20 : 1; Thermal 100 : 1; DP often 3–5 : 1 |
| Pressure Rating (MAWP) | Maximum allowable working pressure of meter body. | ANSI #150–#900 (2–15 MPa) common |
| Temperature Limits | Sensor & electronics survivability. | –200 °C cryogenic Coriolis to +450 °C steam DP |
| Viscosity Range | How fluid rheology affects measurement; high-viscosity may dampen sensor signals. | Coriolis to 20,000 cP; turbine < 10 cP |
| Process Connections & Line Size | Flanged, threaded, Tri-Clamp; DN4–DN300 typical for direct mass meters. | Match to piping standard & sealing class |
| Installation Effects | Straight-run requirements, mounting orientation, vibration sensitivity. | Coriolis minimal straight run; DP needs 10–20 D upstream |
| Outputs & Communication | 4-20 mA, pulse, HART, Modbus, FOUNDATION Fieldbus, Profibus. | Ensure compatibility with DCS/PLC |
| Certifications | ATEX / IECEx for hazardous areas, OIML R 117 / MID for custody transfer. | Verify specific fluid, zone, SIL level |
3. Selection Tips
Start with the fluid: corrosive acids → choose Coriolis in Hastelloy; dry compressed air → thermal.
Define the measurement objective: custody transfer demands highest accuracy; process control may trade precision for cost.
Check turndown vs. normal/maximum flow: undersized meters increase pressure drop, oversized reduce signal‐to‐noise.
Consider installation constraints: space for straight-run, pipe vibration, orientation (multiphase risk).
Factor total cost of ownership: initial price + calibration interval + pressure drop energy losses.
4. Typical Datasheet Snapshot (Coriolis DN50 Example)
| Parameter | Value |
| Flow Range (Mass) | 0–50 000 kg/h |
| Accuracy | ±0.1 % of rate |
| Repeatability | ±0.05 % |
| Density Range | 0–5 g/cm³ |
| Process Temp. | –50 … +200 °C |
| Pressure Rating | 10 MPa (ANSI #600) |
| Wetted Materials | 316L SST tubes, 318LN manifold |
| Signal Outputs | 4–20 mA, HART 7, pulse/freq., Modbus RTU |
| Approvals | ATEX II 2G Ex d IIC T4, SIL 2 |
Conclusion
Mass flow meters allow direct, high-confidence measurement of material transfer, improving both process control and accounting accuracy. Coriolis remains the universal high-performance choice; thermal flow meters excel in gas utility monitoring; while DP-based solutions leverage existing fittings for cost-effective steam and high-temperature applications. Matching the meter’s technical envelope to your fluid, range, and regulatory requirements is the key to reliable, life-cycle-long performance.
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