Weld Inspection – Destructive Testing vs. Non Destructive Testing

When it comes to welding certifications and job site testing there are two methods for testing the quality of the weld. Destructive Testing or “DT” and Non Destructive Testing or “NDT”. Both methods have their advantages and disadvantages!


Destructive Testing or “DT”

For most welding certifications given at a welding school the method used is typically destructive testing. This is a low cost and accurate way to find out if the welding student is making good quality welds. The most common is a coupon bend test. This is done by taking the weld test and cutting it up into strips, then bending them to see if the weld holds up. There are many rules concerning the amount the weld coupon can open up or even break. The ideal bent test coupon should show no signs of defects or opening up. There are many other destructive testing methods but the bend test is the most widely used!




Non Destructive Testing or “NDT”

When it comes to job site testing many welding shops use different methods depending on the type of work done. When it comes to Non Destructive Testing or “NDT” there are many ways to test the quality of the weld. The three most common methods are:

  • Visual weld inspection.
  • Liquid dye penetrant testing
  • Radiographic testing or x-ray

Visual weld inspection is the most cost efficient of the NDT methods but at the same time it relies on the sole discretion of the inspector. This method is mostly used for non critical welding inspection and cannot detect internal weld defects.

This is a welding inspection camera used to find visual defects that are difficult to get too.

Visual weld inspection is the most cost efficient of the NDT methods but at the same time it relies on the sole discretion of the inspector. This method is mostly used for non critical welding inspection and cannot detect internal weld defects.

Liquid dye penetrant testing involves the cost of the dye but it is excellent at detecting surface defects. All this method does is highlight any surface defects.

When it comes to Radiographic testing or x-ray weld inspection the cost is much higher and there are also associated risks with this type of weld inspection. This type of weld inspection will show any type of weld defect and is the most accurate way of inspecting weld quality. The down side is x-ray weld inspection is it uses radioactive materials. Do Not Enter an Area that is labeled X-Ray or Radiographic Testing! Just the slightest bit of exposure to gamma-rays and or x-rays will cause death in the near future! This type of weld inspection is only used when the safety of the public is at risk and the people conducting it are extremely qualified to do this type of work!


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