On clean steel anyone can measure. The difference between one instrument and another shows on cast iron, composites, corroded surfaces and hot walls: there, feasibility must be verified, not declared.
- ✓ High penetration for cast irons, composites and attenuating materials
- ✓ A-Scan to validate the reading when the echo is weak
- ✓ Dual-element probes for corroded and irregular surfaces
- ✓ Dedicated probes and couplants for high-temperature surfaces
Every material opposes a certain attenuation to ultrasound. In steel the pulse travels with modest losses and the back-wall echo returns sharp; in a lamellar graphite cast iron, in a fibre laminate or in a filled rubber, much of the energy is scattered along the path and what returns is a weak signal, sometimes indistinguishable from background noise.
The instrumental response is twofold: lowering the frequency, because low frequencies penetrate attenuating materials better, and increasing the transmission energy. This is the principle on which so-called high-penetration instruments are built, sacrificing resolution in exchange for the ability to pass through the material.
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A second group of difficulties concerns not the material but the surface. A corroded wall is no longer flat: the coupling becomes irregular and the back wall, hollowed by pitting, reflects in directions other than the one of origin. Here dual-element probes are needed, along with the ability to recognise an unreliable reading.
The in-depth topics of this section
| Topic | What it answers |
|---|---|
| Cast irons and highly attenuating alloys | Why the structure of the material scatters the beam |
| Composites and plastics | Low frequency, high energy and verification on a sample |
| Corroded surfaces and pitting | How to measure where the back wall is no longer flat |
| High-temperature measurements | Limits of probe and couplant, and correction of the reading |
The method: verify before, not after
On these materials no datasheet can guarantee in advance that the measurement will succeed: composition, fillers, porosity, temperature and finish change the acoustic behaviour even within the same family. The only reliable verification is a test on a real sample.
This is how we prefer to work: assessing feasibility together before purchase, with the material in hand, instead of discovering a limit when the instrument is already in the workshop. Write to us from the Contact page describing the case.
Frequently asked questions
Because the material strongly attenuates the ultrasound and the return echo arrives too weak to be recognised. A lower frequency and a higher transmission energy are needed.
Yes, with dual-element probes and after removing flaking rust and loose deposits. The reading must in any case be validated, because a hollowed back wall reflects irregularly.
By testing on a real sample of the material, preferably of known thickness. It is the only way to ascertain that the echo is usable and to obtain the actual speed of propagation.
Go back to NDT Technologies and Standards or write to us from the Contact page.
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).