In the machine shop and steelwork ultrasonic testing does two distinct jobs: it verifies that the weld is sound and that the incoming material has the thickness declared by the supplier. The second is the more underestimated, and the more profitable.
- ✓ Angle beam shear wave probes and 45°, 60° and 70° wedges for welds
- ✓ 16-point DAC and TRIG for evaluating the indication
- ✓ Thickness verification on incoming plate and sections
- ✓ Inspection of castings and forgings before machining
- ✓ Velocity Mode for the nodularity test on ductile iron
- ✓ Entry-level instruments requiring no specialist training for the warehouse
A plate declared as 12 mm that measures 11.4 falls within the rolling mill’s commercial tolerance, but if the structural calculation was made on the nominal value the margin has already been spent before work even begins. The same applies to a section, a tube or a casting that arrives with insufficient machining allowance: the problem is discovered once machining is under way, when the part has already cost machine hours.
A goods-inwards check with an ultrasonic thickness gauge settles the question in a few seconds per part, requires nothing to be cut and requires no certified inspector: on the entry-level models of the ZX range you set the material and measure. It is the quality check with the best ratio between cost and risk avoided that a workshop can introduce.
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Weld inspection, by contrast, is an activity different in nature: it requires angle beam probes, a flaw detector and personnel qualified to EN ISO 9712. It is not the same instrument and it is not the same trade — confusing the two is the most common mistake at the purchasing stage.
The application cases of the sector
| Application case | What is inspected |
|---|---|
| Ultrasonic testing of welds | Cracks, inclusions and lack of fusion in welded joints |
| Goods-inwards quality control | Correspondence between declared thickness and actual thickness |
| Thickness verification on plate and sections | Flat and shaped semi-finished products, before machining |
| Inspection of castings and forgings | Machining allowance, internal defects and nodularity of cast iron |
Thickness gauge or flaw detector?
They are two families of instruments with different purposes, and the wrong choice is paid for twice: with the expense and with the inspection that cannot be carried out.
- The thickness gauge measures how much material there is under the probe, vertically. It does not look for flaws
- The flaw detector sends the beam at an angle and locates internal discontinuities
- Welds require shear wave probes and angle wedges, not a dual element probe
- Evaluating the indication requires DAC and an operator qualified to EN ISO 9712
Some high-end models, such as the CMX10-DL, offer flaw prove-up functions: useful for qualifying an indication, but not a substitute for a flaw detector.
Dakota NDT instruments for the sector
| Instrument | When it is the right choice |
|---|---|
| Dakota FX70-DL / FX71-DL | Weld inspection in the field, with A-Scan, B-Scan and dual mode |
| Dakota FX81-DL | Benchtop version with a large display, for the laboratory and the workshop |
| Dakota ZX-1 | Goods-inwards inspection: used without specialist training |
| Dakota CX2 | 39 preset materials: quick verification of plate and sections |
| Dakota ZX6-DL | Velocity Mode for the nodularity test, with a data logger |
| Dakota PMX4-DL | Castings, cast iron and strongly attenuating materials |
Reference standards
- EN ISO 17640 — ultrasonic testing of welded joints
- EN ISO 11666 — acceptance levels in the ultrasonic testing of welds
- EN ISO 9712 — qualification and certification of NDT personnel
- EN 14127 — ultrasonic thickness measurement
- ASTM E797 — thickness measurement by the contact method
- EN 15317 — verification of thickness measuring equipment
Frequently asked questions
No. The thickness gauge measures the material under the probe in the vertical direction and is not designed to locate internal discontinuities. Inspecting a weld requires a flaw detector with shear wave angle beam probes, which send the beam at an angle through the weld bead. Some high-end thickness gauges offer prove-up functions, useful for qualifying an indication but not a substitute for a flaw detector.
For a simple thickness check on plate and sections, no: instruments such as the ZX-1 are set by scrolling to the material’s velocity and are used without specialist training. EN ISO 9712 certification becomes necessary when the inspection has the value of a formal NDT acceptance test, in particular on welds.
Yes, with due care. Cast iron attenuates the ultrasound more than steel and the sound velocity varies with the degree of nodularity, so a generic setting alone is not enough. The Velocity Mode found on some models makes it possible to derive the actual velocity on a sample of known thickness and is also used as an indirect nodularity test.
The investment is that of an entry-level instrument in the range plus a reference block, and it requires neither dedicated personnel nor lengthy training. The comparison has to be made with the cost of machining an out-of-specification semi-finished product, which includes machine hours, material and delay on the order.
To set up a goods-inwards inspection or to choose the flaw detector suited to your welds, write to us stating the material, the thicknesses and the acceptance standard.
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
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