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Weld Joint NDT

Weld Joint NDT

Butt welds require a specific set of NDT procedures in order to ensure a complete assessment of flaws. These kinds of welds are susceptible to distortion, cracking, corrosion that can degrade the overall integrity of the assets. Within the world of NDT the most preferred techniques often include radiographic testing (RT), phased array ultrasonic testing (PAUT), and (Eddy current array) ECA. But the question arises that what is the best method to be used for butt weld joints.

Best NDT Method for Testing Butt Welds

There is no one best NDT method for testing butt welds. Rather certain methods work best in certain situations.

Radiographic Testing of Butt Welds

Radiographic testing uses a tube to produce X-ray or a gamma rays source these rays are indicated on the welded materials to capture image of the object on a photographic film. If a welded joint shoes cracking it will appear dark outline on a radiographic film. Using radiographic testing analyst can expose a variety of flaws for butt weld, such as cracking, porosity, voids, overlap etc. However, it is important to note that RT has significant drawbacks, including:

  • Health hazards due to radiation exposure especially for a longer period.
  • Reduced efficiency as the testing time required is significantly more than other methods
  • Difficulty in determining the depth of flaw until the test is performed form various angles

PAUT of Butt Welds

Ultrasonic testing offers great adaptability and accuracy and is ideal in a great instance when depth and penetration is a high priority. While standard UT is effective in scanning welded joints but it doesn’t offer the high level of customization that PAUT can offer.

PAUT is ideal for inspecting comprehensive and challenging welds such as stainless steel and austenitic welds. Since austenitic weld contains a high amount of grain reflections that generate distortions in the data, analysts require a PAUT probe that can penetrate weld joints without producing incomplete reflection. PAUT is also capable of providing low-frequency options that helps analysts counter propagation issues caused by high attenuation.

ECA of Butt Welds

As seen earlier PAUT may be more adept at detecting discontinuities on a volumetric level that other NDT techniques, few approaches come close to ECT (eddy current testing) in detecting surface defects in welding joints. ECT is well suited for detecting thinner welds which are more difficult to detect with UT or PAUT technique.

Specialized ECA technology can offer a great advantage such as:

  • Enhanced accuracy and coverage
  • Routable scanners can pinpoint flaw location and characterize flaw dimension
  • offers greater stability during testing

ECA has a few limitation one such limitation is that as the operator moves the probe across the material the excitation coil need to be close to the material surface for accurate detection and signal quality. It can be quite challenging when dealing with complex geometries, different weld shapes, and materials, rough surface conditions as inspections areas are difficult to reach.

ECA is more advanced and proffered to inspect butt weld. probes having the ability to inspect welds with complex geometries using multiple array coils can make a significant difference. The array coils allow users to cover more surface area and reading heat-affected zones. Looking for a probe design that keeps the coils or other sensors closely and properly aligned with the surface of the material as the operator slides over it.

for the best results, analysts need a handheld device that boasts an industry-leading signal quality. when combined with surface array capabilities, users can achieve rendering of weld detect and reduce inspection time significantly.

Improving Butt Weld Inspections

As seen earlier if welding is to be inspected on a volumetric level, ultrasonic testing is ideal. Radiographic testing is a deal for testing surface and internal aberrations. But for inspecting surface and subsurface defects eddy current testing is the ideal solution as being most effective.

While choosing the right approach it is vital to conduct an effective and efficient inspection. Regardless of the inspection techniques being used, it is vital to ensure the highest level of inspection confidence and data quality.

  • Created 01-Apr-2020