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Ultrasonic technology in pipeline condition assessment

Our technology explained

Within our tool range, we utilize ultrasonic technology to detect over 10 different failure mechanisms and/or characteristics in pipelines of all types of materials.

Our technology explained

Ultrasonic Technology

The usage of ultrasonic technology has been scientifically proven to be an effective and non-destructive way for assessing the condition of a pipeline in other sectors such as the oil & gas industry. It involves the use of high-frequency sound waves beyond the range of human hearing. On the bottom of this page there are links to several studies regarding this topic.

Principles of operation 

Our inspection tools are equipped with ultrasonic sensors that operate by emitting pulses of high-frequency sound waves towards the pipeline wall. As these waves travel through the material of the pipe wall, they reflect back to the sensor at the front and the back of the pipewall. The duration taken for the sound waves to complete this round trip and the amplitude of the returning waves offer valuable insights into the material’s characteristics. This includes details about thickness, density, and the identification of potential anomalies within the pipeline.  

Figure 1 Principle of ultrasonic measurement

When it reaches the inside of the pipe wall (front wall), a portion of the ultrasonic signal reflects back to the sensor. The other part moves through the pipe wall until it reaches the outsideof the pipe wall (back wall). Here, the same process occurs again: a portion of the signal reflects back and returns to the ultrasonic sensor, and the other part continues beyond the pipe wall. 

Figure 2 Schematic representation of ultrasonic signals reflecting on the pipe wall

Such an ultrasonic measurement can then be represented in a so-called A-scan (Amplitude scan). This scan displays the amplitude, indicating how much energy of the ultrasonic signal has returned to the sensor. Additionally, it shows how much time it took to travel through the beginning and end of the pipe wall and return to the sensor (see A-scan figure). 

Figure 3 A-scan

On the X-axis, time is represented, and on the Y-axis, the amount of energy is displayed. In the figure, two peaks in the signal are visible. The first peak represents the front wall, and the second peak the back wall. From this information, the distance between the front wall and the back wall can be deduced to calculate a wall thickness. 

Failure mechanisms measured 

With the use of these ultrasonic sensors we can identify and classify repair pieces, pipe material, curves, bends, T-pieces and joint types as well as detect the following failure mechanisms in pressurized pipelines:  

  1. Corrosion in metals; 
  2. Leaching in AC; 
  3. H2S deterioration; 
  4. Delamination of multilayer pipe walls; 
  5. Thickness measurement of internal liners;
  6. Joint gap width; 
  7. Ovality; 
  8. Debris or scaling in the pipe; 
  9. Gas and air pockets. 

By combining ultrasound measurements with other sensors our tools can measure the following additional failure mechanisms and characteristics: 

  1. Angular displacement of joints;
  2. Deformation in length (axial) direction of the pipeline;
  3. X, Y, Z location of the pipeline.

Advantages of ultrasonic technology in pipeline assessment 

  • Non-destructive: the ultrasonic sensors don’t damage the pipeline or internal liners during inspection; 
  • Accuracy: ultrasonic measurements provide accurate information about the thickness of the pipe and the presence of anomalies. For example, we measure wall thickness with an accuracy of 0,49mm and pipe ovality with an accuracy of 0,5%-point; 
  • Versatility: ultrasonic technology is versatile and can be used on all pipe materials, such as concrete, asbestos cement, cast iron, ductile iron, steel and HPDE/PVC/GRP; 
  • Early detection: the technology can identify potential issues at an early stage, preventing more significant problems and ensuring proactive maintenance. 
  • Comprehensive assessment: it provides a comprehensive assessment of the entire pipeline, including the joints, helping to prioritize maintenance efforts. 

How we equipped our inspection tools 

Within our inspection tools, we utilize multiple ultrasonic sensors, along with an MFW sensor, an IMU and a hydrophoneto provide a full condition assessment of the pipeline of any material, such as concrete, asbestos cement, cast iron, steel and HPDE/PVC/GRP.

MFW sensor  

The MFW sensor on our tool, magnetic field wave sensor in full, acts as a coil that electromagnetically resonates with the spiral wound wire in the prestressed concrete, that basically also acts as a coil. If a coil turn of the spiral wire is broken, we can pick up the loss in signal. Several projects with verifications have proven that we can even detect single coil turn breakages. 

Figure 5 Schematic representation of a coil in a reinforced concrete pipe


An IMU (Inertial Measurement Unit) is a device that uses accelerometers, gyroscopes, and magnetometers to measure how fast something is moving and how it’s rotating. These sensors work together to figure out how an inspection tool is positioned and oriented in a pipeline. 

Accelerometers measure movement in three directions, gyroscopes measure how something is rotating (yaw, pitch, roll), and magnetometers measure magnetic fields in three directions. By combining these measurements, the IMU can accurately track how the inspection tool is moving and rotating in the pipeline, even when there’s no GPS signal underground. The IMU is helpful for figuring out the X, Y, and Z (depth) position of the pipeline, detecting any differences from existing digital GIS (Geographic Information System), analyzing how much something is turning, and determining if plastic pipe parts are bending. It also provides extra information to identify specific materials or properties in the pipeline, like repair clamps. 

Figure 6 Schematic representation of an IMU 


A hydrophone is a specialized underwater microphone designed to detect and record sound waves in water. Hydrophones are sensitive to acoustic signals underwater, allowing them to capture sound waves due to the turbulence and pressure changes, such as escaping fluids when there is a leak in a pipeline. Our tool is equipped with a hydrophone and we can pinpoint leaks (>13.0 dB) by comparing the baseline acoustic signals with the altered ones caused by a leak.

Figure 7 Hydrophone 


When we perform an inline inspection, we also determine the exact XYZ location of a pipeline with an accuracy of 0,5 meter.  

GPS System 

In order to detect the exact XYZ location accurately, we have further equipped our inline inspection tools with a high-end GPS system. This system operates by having our inspection team walking the entire pipeline route to be inspected. Every 100 meters, the location of the tool is calibrated using a tracker carried by the team above ground. 

Odometry wheels 

Next to that, on our Acquarius tool, we added odometry wheels. These odometry wheels, also known as odometry sensors or encoder wheels, measure how a vehicle or tool changes position by tracking the rotation of its wheels or moving parts. In in-line inspections of water pipelines, odometry helps accurately measure how the inspection tool moves in a straight line. The inspection tool has wheels that touch the inside of the pipeline. 

As the inspection tool moves, the wheels turn, and we keep track of how many times they spin. This helps us figure out the lengths of pipeline sections, the total distance the inspection tool travels, and how fast it’s moving. When combined with the IMU, odometry also helps determine the X, Y, and Z position of the pipeline. 

Figure 8 Rear view of the Acquarius with mounted odometry 

XYZ mapping in data analysis 

During data analysis, done by our own data analysis team, we combine the data gained from the odometry wheels and GPS with the data attained from the IMU, to establish an accurate XYZ-mapping. To know the exact XYZ location is important for water utilities when they need to, for example, excavate the pipeline.  

XYZ-mapping is essential when it comes to accurately aligning the data acquired from our ultrasonic sensors with the XYZ-mapping data. Precision in this is crucial, as it allows us to pinpoint the exact locations of measured failure mechanisms and anomalies. 

Published scientific research and whitepapers

AC Sulphate attack validation

Widely used for water distribution and sewage systems due to cost-effectiveness and durability, asbestos cement (AC) pipelines face vulnerability over time, especially to sulphate attacks that degrade the cement matrix. Acquaint BV has been a leader in inspecting AC pipelines since 2016, using advanced ultrasound technology. In 2017, they discovered clear evidence of a sulphate attack in AC pipelines. This white paper outlines findings from Acquarius inspections on sulphate attacks in asbestos pipelines, validated comprehensively through drill core samples.

Read full whitepaper

AC Leaching validation

Asbestos cement pipes, widely used in water and sewage systems for their strength and durability, face risks as they age due to calcium leaching from environmental exposure, particularly water. This compromises their structural integrity, leading to potential failures and water contamination. This report compares ultrasound and CT scan techniques for quantifying and visualizing calcium leaching in asbestos cement pipes, aiming to provide insights into their applicability and effectiveness in assessing pipeline condition and remaining service life.

Read full whitepaper

CT Scans of Asbestos Cement Pipes as a Reference for Condition Assessment of Water Mains

In this research the use of X-ray computed tomography (CT) is explored for assessing the degradation of AC pipes from the field. CT scans reveal detailed insights, highlighting the importance of comprehensive understanding of pipe degradation. The study validates CT through comparisons with strength tests and a commercial inspection technique, showcasing its utility for detailed measurement of pipe degradation crucial for water utilities. 

Read full research

Ultrasonic inline inspection of a cement-based drinking water pipeline

This study suggests a method to translate ultrasonic signals from pipeline inspections into degradation levels for a cement-based drinking water system. Using data from a Dutch water main, it automates the process to estimate relative degradation levels and visualize the degraded condition. The study emphasizes the importance of considering the speed of sound in cement for determining degraded depth, while acknowledging the need for further research on absolute degradation levels. 

Read full research

Detection of acidic deterioration in cement-based water pipes with ultrasonic pulse-echo technique

The study aims to assess the condition of the Dutch drinking water network, focusing on identifying assets near the end of their lifespan. Using ultrasonic testing, the research specifically examines degradation in cement-based pipes due to acidic attacks. Measurement involves ultrasonic pulse velocity in mortar blocks exposed to hydrochloric acid. The study highlights key factors in detecting acid-induced damage, emphasizing the suitability of a transducer for this purpose. 

Read full research

Without the Acquarius, we would probably have dug up many more pipelines to inspect. Now we know that won’t be necessary.
Fred Bergman Maintenance employee Civil Engineering and Architecture at Water Board Aa en Maas
Fred Bergman

Water board 'Aa en Maas'

Do you, want to move towards 100% predictability? Contact Erik.


Can the Acquarius go through bends?

The Acquarius is even capable of traversing through sharp-angled bends.

Can the Acquarius inspect pipelines while the pipeline is in operation?

Yes the Acquarius can inspect a pipeline while it is in operation

Can the Acquarius measure multiple materials simultaneously?

Before the inspection, the Acquarius is equipped with the appropriate sensors to measure the known materials from the to-be-inspected pipe.

Can the Acquarius pass through a pipe consisting of multiple diameters?

The Acquarius can handle a 25% change in diameter as standard, this can be increased to a maximum of 50% if necessary.

How do you launch the Acquarius?

The Acquarius is launched with a pig trap and water pressure in the pipe.

How is the Acquarius composed?

The Acquarius consists of a flexible foam prop in which front and rear sensors and electronics are placed.

After an inspection, how long does it take until the report is delivered?

Around three weeks.

more questions


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