Understanding Different Non-destructive Weld Inspection Methods
The process of welding often introduces metallurgical defects and contaminants into the weld. If a weld needs to withstand severe stress and loading conditions, it must meet certain minimum quality standards. This is why it is critical to evaluate the integrity of welds, which can be done by destructive as well as non-destructive methods. The most common non-destructive weld inspection methods are Liquid Penetrant, Visual Inspection, Eddy Current, Ultrasonic, Radiography, and Magnetic Particle.
Non-destructive weld testing is extremely essential because destruction of a weld for the purpose of testing requires it to be replaced by a new weld. The outcome of weld failure can range from minor to extreme. In many instances, failure of weld applications may cause serious harm. This is why these applications require a high level of testing capabilities.
Mentioned below are some of the most commonly used non-destructive weld inspection methods.
In this method, inspectors observe the weld pool and the cooling metal while the welder is at work. Inspectors typically look for undercutting, inclusions, depth of weld penetration, and bonding to the parent metal. When a non-complying defect is found by the inspectors, they mark the spot. The defect is ground out at the end of the weld run and the weld is reconstructed as per the required quality.
Liquid or Dye Penetrant Inspection:
As the name suggests, this method detects weld defects using a colouring agent. However, please note that only surface cracks and surface discontinuities can be detected by this inspection. The testing area is isolated in this test, and then the inspector tries to pass fluid through it. The weld is considered to be secure if the fluid refuses to pass through the weld. On the other hand, if there are cracks or flaws within the weld, fluid will run through it.
This NDT weld testing is highly preferred for its speed and capability. A transducer is used to introduce high-pitched acoustic waves into a weld. The transmission of these sound waves can be altered by the presence of cracks, voids, or warps in the weld. When the waves encounter any type of discontinuity, they bounce back and are detected by a probe. This method is not suitable for detecting surface and near surface faults.
Magnetic Particle Testing:
In this testing methodology, the interior of ferromagnetic objects is examined by studying how they impact magnetic fields. An induced magnetic field is allowed to travel through the weld material. The presence of flaws or irregularities is indicated by how the magnetic field gets impeded by them. Paint must be removed before this testing because it is not ferromagnetic. Readings may also get affected by other surface irregularities.
Eddy Current Testing:
This testing method is similar to magnetic particle testing as it detects faults relying on electromagnetism. However, unlike magnetic particle testing, Eddy current method requires no surface preparation. Therefore, this method can be applied for painted surfaces without the hassle of removing the paint.
If you are looking for a trusted welding inspection and NDT service provider in Australia, please contact us at Coating Management Solutions (CMS).