Portable Ultrasonic Flow Meters for Large Diameter Pipes

On-site flow measurement for large-diameter pipelines is often constrained by requirements such as water supply shutdowns or the need to cut into the pipe, making flexible operation difficult. For pipelines with a diameter of DN1600 or larger, handheld ultrasonic flow meters utilize a non-invasive, clamp-on measurement method; this allows flow to be measured directly from the outer pipe wall without damaging the pipeline.

Next, focusing on the challenges of flow measurement in large-diameter pipes, we will introduce the features, operating principles, and specifications of the handheld ultrasonic flow meter. We will also demonstrate practical procedures for using the device to detect leaks in drinking water pipelines.

RFQ

Challenges in flow measurement for large-diameter pipelines

Features of Portable Ultrasonic Flow Meters

Handheld ultrasonic flow meters take non-contact liquid flow measurements, covering pipe sizes from 20 to 6000 mm (0.5–236 inches). Thanks to this non-contact design, the device is lightweight and easy to carry around. Its key features are listed below:

• Portable and non-intrusive. Magnetic ultrasonic sensors attach directly to the outside of pipes to carry out flow measurement, no pipe cutting required.
• Rechargeable power supply. Equipped with a large-capacity Ni-MH battery, supporting up to 24 hours of continuous operation.
• Wide measurement range. Users can swap different sensor models to measure pipes ranging from DN15 up to DN6000.
• Reliable high accuracy. Measurement accuracy reaches better than ±1%, with linearity of 0.5% and repeatability of 0.2%.
• Built-in data logger. It comes with 24K byte storage that can save up to 2000 sets of measurement records.

Technical specifications of handheld ultrasonic flow meters

Working principle of handheld ultrasonic flow meters

Portable ultrasonic flow meters operate based on two principles: the time-difference method and the Doppler effect.

Transit-Time Method

Two ultrasonic transducers are mounted on opposite sides of the pipe, acting alternately as transmitters and receivers to send and receive ultrasonic signals.

If the fluid inside the pipe stays static, ultrasonic waves take the same amount of time travelling downstream and upstream. When the fluid flows, the wave travelling with the flow spends less time, while the wave against the flow takes longer. This creates a time difference Δt between the two paths.

The device measures this time difference. Combined with the known sound velocity C in stationary fluid and transducer separation distance L, it calculates the flow velocity V. Multiplying velocity by the pipe’s cross-sectional area gives the volumetric flow rate Q.

Core Formulas (Single/Dual Path)

Downstream time: T1 = L / (c + v cosθ)

Upstream time: T2 = L / (c − v cosθ)

Time difference: ΔT = T1 − T2 ≈ 2Lv cosθ / c² (when v ≪ c)

Flow velocity: v = (L / (2 cosθ)) × (ΔT / (T1T2))

v = (D / (2 sinθ cosθ)) × (ΔT / (T1T2)) = (D / (sin2θ)) × (ΔT / (T1T2))

Volumetric flow rate: Q = v × A = v × π(D/2)²

L: Acoustic path length (single path).

D: Inner diameter.

θ: Angle between the acoustic beam and the pipe axis.

c: Speed ​​of sound.

v: Average flow velocity.

ΔT = T_up − T_down

Doppler Effect Method

When ultrasonic waves hit suspended particles or bubbles moving along with the fluid, the frequency of the reflected wave changes. This frequency shift is known as the Doppler effect.

Doppler frequency shift. Due to the motion of the scatterers, the frequency of the reflected wave shifts by Δf; the magnitude of this shift is directly proportional to the flow velocity, v.

The formula is: Δf = f₂ − f₀ ≈ 2 f₀ v cosθ / c
Flow velocity v = (Δf · c) / (2 f₀ cosθ)
Flow rate Q = A · v = (π D²/4) · v

Where:

f₀: Transmitted frequency (Hz)

f₂: Received frequency (Hz)

Δf: Frequency shift (Hz)

v: Fluid flow velocity (m/s)

c: Speed ​​of sound in the fluid (m/s)

θ: Angle between the sound beam and the flow velocity vector (°/rad)

D: Pipe diameter (m)

A: Cross-sectional flow area (m²)

Q: Instantaneous flow rate (m³/s)

Applications of Portable Ultrasonic Flow Meters

Pipeline Network Leak Detection

In urban water supply systems and older urban areas, water supply pipelines are prone to aging and leakage. Handheld ultrasonic flow meters assist water supply authorities in monitoring urban water usage.

Industrial circulating water systems

Used for routine flow checks on factory cooling water, chilled water and circulating water pipelines.

Wastewater treatment

Handheld Doppler-type ultrasonic flow meters can measure wastewater carrying suspended solids and impurities.

Petrochemical industry

Suitable for pipelines transporting process liquids, solvents and oil products, provided the medium is non-corrosive and free of excessive air bubbles.

How are Portable Ultrasonic Flow Meters used for leak detection in drinking water pipelines?

Handheld ultrasonic flow meters can rapidly pinpoint leak locations in drinking water pipelines through non-contact, portable, and multi-point measurements.

Preliminary Preparation
Clean the outer surface of the pipe, removing paint, rust, and debris.
Apply specialized ultrasonic couplant to eliminate air gaps.
Verify pipe material, outer diameter, wall thickness, liner type, and fluid type (potable water).

Selecting the Measurement Mode
Since drinking water is typically clear, the transit-time method is the preferred choice. If the pipe diameter is large or the signal is weak, select the appropriate handheld (or clamp-on) configuration.

Installation and Measurement
Place the transducer vertically against the pipe wall, as close to the pipe centerline as possible.
Enter the pipe parameters. Select the appropriate mode to measure flow velocity and flow rate.
Perform repeated measurements at multiple points。

Data Analysis and Leak Localization
Determine the location of the leakage.
Compare design flow rates with measured flow rates, or analyze flow rate differences between different points.

Pinpoint the leak location.
Incorporate supplementary information such as minimum night-time flow and pressure fluctuations.

A Spanish contractor specializing in drinking water network leak detection required a solution to measure flow rates in DN250–DN1600 pipelines without interrupting the water supply or cutting into the pipes. We recommended the handheld transit-time TUF-2000H flow meter equipped with clamp-on transducers, suitable for single, homogeneous liquids within a temperature range of -30°C to 90°C. As the pipe diameter range spanned two transducer size categories, the solution included two sets of sensors: medium and large. The device operates on a built-in battery and does not provide real-time signal output; instead, measurements rely on comparing readings taken at multiple points on-site.

For flow measurement requirements involving large-diameter pipelines (DN1600 and above), a handheld ultrasonic flow meter is the ideal choice. It offers advantages such as non-destructive clamp-on installation, no need to shut off the water supply or cut into the pipe, and excellent portability. Additionally, the device supports various installation configurations.

Sino-Inst is dedicated to providing customers with customized flow measurement solutions for large-diameter pipelines. Our handheld ultrasonic flow meters are widely used for measuring flow in a variety of liquid pipelines. Please feel free to contact us if you have any flow measurement needs!

More Flow Measurement Solutions

Zhang Wei

Zhang Wei, possesses 20 years of experience as an automation instrumentation engineer, specializing in the research, design, installation, commissioning, and maintenance of automation instruments.

Face to various instrument communication protocols (such as Modbus, Profibus, etc.), with solid hardware circuit design and software programming skills (proficient in C language and PLC programming). Has extensive project experience; projects he has led and participated in have all achieved outstanding results, improving product accuracy, reducing costs, and increasing production efficiency.

Possesses excellent communication and coordination skills and a strong team spirit, enabling him to quickly respond to customer needs and provide high-quality automation instrumentation solutions.