On buried tanks and water networks corrosion attacks from two sides: the soil outside and the water inside. Where the wall is accessible, ultrasonic measurement says how much steel is left.
- ✓ Remaining thickness measured without emptying or taking out of service
- ✓ Echo-Echo mode to measure through the protective coating
- ✓ Scan mode to find the thinnest point quickly
- ✓ Stored mapping for calculating the remaining life
A buried tank is exposed to two mechanisms at once. On the outside the soil, with its moisture and its composition, attacks the wall where the coating was damaged during installation or has degraded over time. On the inside the product held works on the same walls, at different rates depending on the area.
In water networks the picture is the same: steel mains lose thickness on the inside through the water and the deposits, and on the outside through contact with the soil. In the stretches that can be inspected, in chambers or manholes, ultrasonic measurement turns a subjective judgement into a number.
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The operational limit is accessibility: the probe has to rest on a surface that can be reached and is reasonably clean. Where the wall is not accessible, ultrasonic thickness measurement does not apply and the assessment has to rely on other techniques. Where it is, it returns the figure on which the work is planned.
Where to concentrate the readings
| Area | Reason for the inspection |
|---|---|
| Bottom generatrix of the tank | Internal stagnation and build-up of deposits |
| Support areas and saddles | Contact with the soil and retention of moisture |
| Passages in chambers and manholes | Accessible points representative of the buried stretch |
| Nozzles and branch connections | Geometric discontinuity and local turbulence |
| Stretches with damaged coating | Accelerated external attack where the protection has failed |
Setting up the measurement campaign
The surface needs preparing only as much as necessary: removing flaking rust and loose deposits is enough, while an adherent coating can stay if the instrument has Echo-Echo mode. With scan mode the area is swept in search of the minimum, then the reading is recorded at the point found.
Each point has to be identified and marked on a drawing, because the isolated value says little: what the network operator needs is the change between two campaigns, from which the thinning rate is derived and the replacement of the stretch is planned.
Recommended instruments
| Instrument | Typical use |
|---|---|
| Dakota CMX1-DL | Measurement of metal and coating with 4 GB data logger |
| Dakota CX4 | Measurement through the coating with Echo-Echo ThruPaint™ |
| Dakota CX8-DL | Extended campaigns with data logger and B-Scan |
| Dual element transducers | Twin-crystal probes for corroded and uneven surfaces |
Frequently asked questions
Yes. The measurement is taken from outside and the presence of liquid inside does not prevent the wall thickness from being read.
Ultrasonic thickness measurement requires contact between probe and surface. On stretches that cannot be reached, the work is done at the points that can be inspected, such as chambers and manholes, taking them as representative of the stretch.
It is enough to remove flaking rust and loose deposits. An adherent coating can stay, if the instrument has Echo-Echo mode.
Back to Construction and Infrastructure, or write to us from the Contacts page: tell us the material, diameter and access conditions of the stretches to be inspected.
Further information and contacts
Systems division and sensor integration partner : www.roder.it
More information about RODER SRL : about us
Contact for general information : info@roder.it
Contact for information about these products : info@roder.it
The information contained on this web page is provided for information purposes only. Although it has been compiled with the utmost care, it does not constitute a contractual offer or a binding commitment to supply. It may contain transcription, translation or typographical errors. For precise and up-to-date information, please contact our company directly.
Some images on this website have been intentionally generated using Artificial Intelligence (AI). This is because, for many applications and projects, it is not possible to disclose photographs of the installation or of the actual system due to confidentiality agreements, confidentiality clauses and non-disclosure agreements (NDAs).