Ultrasonic Flow Meter Selection Guide

Ultrasonic Flow Meter Selection Guide

1. First Step: Selection of Measuring Principle and Medium Adaptation

Ultrasonic flow meters are mainly divided into transit-time and Doppler types.

1.1 Transit-Time Method (Mainstream & Preferred)

- Applicable medium: clean, single-phase liquids (tap water, pure water, crude oil, heat transfer oil, etc.) with low particles or bubbles (suspended solids ≤100ppm, bubbles ≤5%).

- Advantages: high accuracy (±0.5%~±1%), wide turndown ratio (≥100:1), good stability, suitable for custody transfer and energy metering.

- Not applicable: sewage, slurry, media with high particles or bubbles.

1.2 Doppler Method

- Applicable medium: turbid liquids with suspended particles or bubbles (sewage, ore pulp, paper pulp, wastewater), requiring particles/bubbles ≥100ppm, particle size ≥0.05mm.

- Advantages: strong anti-interference, suitable for dirty media monitoring.

- Disadvantages: lower accuracy (±1%~±5%).

1.3 Key Medium Parameters

- Temperature: standard -20℃~80℃; high-temperature type up to 200℃.

- Pressure: in-line type 1.6~10MPa.

- Corrosiveness: 316L for general use; PTFE or Hastelloy for strong corrosive media.

2. Second Step: Diameter and Number of Channels

2.1 Diameter Selection

Flow rate formula:
Q(m³/h) = 0.002827 × D(mm)² × V(m/s)

- Recommended velocity: 0.1~10 m/s.

- Normal flow should be within 20%~50% of full scale.

2.2 Number of Channels

- Small diameter (DN15~DN100): single channel is sufficient.

- Large diameter (DN300+) or high accuracy: dual / four channels to improve stability.

3. Third Step: Installation Type Selection

表格

Installation Type Application Advantages Disadvantages
Clamp-on Existing pipes, no shutdown, large diameter DN15~DN6000 No pipe cutting, no pressure loss Affected by pipe wall and scaling
Insertion Large diameter DN80+, long-term online monitoring High accuracy, stable Needs drilling during shutdown
In-line (Flow Tube) Small diameter, high-precision metering, new projects Highest accuracy Needs pipe cutting, higher cost

Key Installation Requirements

- Straight pipe requirement: upstream ≥ 10D, downstream ≥ 5D.

- Installation position: install horizontally on the side of the pipe to avoid air accumulation and sediment.

4. Fourth Step: Material and Accessory Selection

4.1 Sensor and Lining Materials

- Sensor: 316L, Hastelloy, Titanium, Tantalum.

- Lining: PTFE, rubber, polyurethane.

4.2 Key Accessories

- Couplant: special ultrasonic couplant required.

- Temperature compensation: standard for transit-time models.

- Heat energy measurement: dual PT1000 temperature sensors.

5. Fifth Step: Electrical and Environmental Parameters

5.1 Power Supply and Output

- Power: 220V AC, 24V DC, battery/solar powered.

- Output: 4–20mA, pulse, RS485 (MODBUS), HART, PROFINET, wireless GPRS/4G/NB-IoT.

5.2 Accuracy Class

- Custody transfer: ±0.5%.

- Process control: ±1.0%.

- Pipeline survey: ±1.5%.

5.3 Environment and Protection

- Protection: IP65 for indoor; IP68 for outdoor, well or submerged.

- Explosion-proof: Ex d IIC T6 for petroleum and chemical applications.

- EMC: keep away from inverters and motors; use shielded cable and reliable grounding.

6. Key Selection Pitfalls to Avoid

- Do not use transit-time type for sewage or slurry.

- Do not use clamp-on type for thick cast iron or heavily scaled pipes.

- Ensure sufficient straight pipes: upstream 10D, downstream 5D.

- Remove rust and coating before clamp-on installation.

- Apply couplant evenly to avoid air gaps.