Ultrasonic testing (UT) sends high-frequency sound into a part and reads what comes back. Reflections from cracks, lack of fusion, inclusions and laminations show where a flaw is and how large it is, from inside the material and without cutting it open.
- Finds
- Internal cracks, lack of fusion, inclusions, laminations, wall loss
- Typical use
- Weld inspection, pressure boundary, forgings and plate, shear wave on structural and concrete assets
What ultrasonic inspection finds
- Cracks and other planar flaws inside welds and base metal
- Lack of fusion and incomplete penetration
- Slag inclusions and porosity
- Laminations in plate
- Internal defects in forgings and castings
- Wall loss from corrosion and erosion (see ultrasonic thickness testing)
Straight-beam testing sends sound straight into plate, forgings and bar to find laminations and inclusions. Angle-beam, or shear wave, testing sends sound in at an angle, which is how welds are examined: it reaches the root and sidewalls of the weld from the surface of the plate. We also apply ultrasonic inspection to concrete structures such as bridge piers and foundations. Where a job needs encoded, recorded data or has difficult geometry, phased array is the next step.
Ultrasonic testing or radiography?
UT is better at finding planar flaws such as cracks and lack of fusion, tells you how deep a flaw lies, needs access from one side only, and involves no radiation, so other work can carry on nearby. Radiography gives a permanent image and shows volumetric flaws such as porosity and slag well. Many codes accept either for weld examination; some specify one.
Where it’s used
- Weld inspection in structural steel, pressure vessels and piping
- Forgings, plate and bar in manufacturing
- Aerospace and defense components
- Power generation and nuclear pressure boundary
- Oil and gas, chemical and petrochemical plants
- Bridges, foundations and other concrete structures
- Maritime and shipbuilding
Codes and standards
- ASME Boiler and Pressure Vessel Code, Section V: Article 4 for welds and Article 5 for materials
- AWS D1.1, which contains its own ultrasonic procedure and acceptance criteria for structural steel welds
- ASTM E164, contact ultrasonic testing of weldments
- ASTM A388/A388M, ultrasonic examination of steel forgings
- ASTM A435/A435M and A578/A578M, straight-beam examination of steel plate
- ASTM E2375, ultrasonic testing of wrought products, common in aerospace
- Customer and prime-contractor specifications
Who does the work
Every Midgard technician who performs ultrasonic testing holds current certification in that method, issued under a written practice. For most industrial work the written practice follows ASNT’s SNT-TC-1A; for aerospace and defense work it follows NAS410. A Responsible Level III oversees the program: approving procedures and technique sheets, examining and certifying technicians, and answering the technical questions that come up on the job.
If your contract calls for a different scheme, such as ANSI/ASNT CP-189 or NAVSEA requirements, tell us when you ask for a quote.
Training in ultrasonic testing
Midgard also trains in ultrasonic testing, along with all the other major methods. Instruction is given at Level I, II and III by certified Level III instructors, to SNT-TC-1A, CP-189, NAS410, NAVSEA or whichever code you certify to, with general, specific and practical examinations at your facility or ours. It suits new hires working toward first certification as well as technicians due for re-examination. See training and certification, or ask about a class.
Common questions
What is ultrasonic testing used for?
Finding and sizing internal flaws in welds, forgings, castings and plate, measuring wall thickness and corrosion, and checking bonded and layered structures. It is one of the most versatile NDT methods because it can see inside thick material from one side.
Does ultrasonic testing need surface preparation?
The probe needs a couplant, usually a gel or water, and a reasonably smooth surface so sound can enter the part. Loose scale, spatter and rough coatings are removed from the scanning area. Tight, well-bonded paint can sometimes stay if the procedure allows for it.
What does ultrasonic testing cost?
It depends on the length of weld or area to be examined, the technique and code, access, and whether recorded data is required. Send us drawings or a description of the scope and the governing code, and we will quote the job.
Is ultrasonic testing safe around other workers?
Yes. The ultrasound used in NDT is harmless to people, so there is no exclusion zone and other work can continue alongside the inspection.
Tell us the material and thickness, the welds or area to be examined, access, and the code you work to. Call 1-844-MIDGARD, email contact@midgardscientific.com, or use the contact page.