Welding Tubing Inspection

Many industries rely on welding and today, several different welding processes are employed and aerospace structures require close evaluation, inspection, and monitoring. Poor welding techniques can present risks and vulnerabilities in many structures. Many industries require welds to be inspected regularly to ensure safety and reliability for industrial systems.

Most engineers prefer nondestructive testing methods. NDT allows components to be tested for serviceability, without impairing their usefulness. The ANSI/AWS D1.1, Structural Welding Code-Steel, states, "Welds subject to the nondestructive examination shall have been found acceptable by visual inspection”, therefore you should Inspect weld joints to ensure the quality of the weld is acceptable and that the part is flight worthy. There are many defects or faults in welds that can occur. Regular maintenance and inspection can help spot common weld faults before they worsen.

Common Weld Faults

• Incomplete Penetration Incomplete root fusion, or incomplete penetration, occurs when both sides root region of the joint are unfused. Bridging occurs in groove welds when the deposited metal and base metal are not fused at the root of the joint. Frequent causes of incomplete penetration include the joint design or the conditions of construction.
• Porosity Porosity is the measure of void spaces in a material. The more porous something is, the more hole it tends to have. They differ from slag inclusions in that the pockets contain gas rather than a solid. These voids created by these little holes are created by gas released by cooling weld because of its reduced solubility temperature drops or by the chemical reactions in the weld. The best ways to prevent porosity is to avoid overheating and undercutting the weld metal, too high a current setting, or too long an arc.
• Undercutting Undercutting is a groove or crater that occurs near the toe of a weld. When this flaw occurs, the weld metal fails to fill in the grooved area near the toe of the weld, which results in a weak weld that is prone to cracking. Common causes of undercutting include an arc gap that is too long, a failure to fill the groove completely or a current adjustment that is too high.
• Slag Inclusions Slang inclusion is the small particle of flux and other solids compounds that become trapped in the weld metal. They produce porosity in the weld metal and prevent full penetration of the weld. This weld defect can be prevented by making sure that the slag rises to the surface of the weld pool, removing all along and to not leave behind any contours.
• Lack of Fusion This weld defect consists of incompletely fused spots that often occur in a welded joint. In this case, molten metal will stick to the base metal that has not melted enough during welding. A joint between the solid phase and the liquid one forms. Lack of fusion can be caused by improper fluxing, dirty plate surfaces, improper electrode size or wrong current adjustment.

Using Borescopes For Welding Tubing Inspection

Nondestructive testing (NDT) is one method used to inspect welds in steel, aluminum, and titanium. NDT testing can be done with a flashlight and a magnifying glass for the surface. However, for internal component inspections in small areas, borescopes are used. SPI Borescopes offers a variety of portable borescopes that can be used to identify cracks, incomplete penetration, inclusions, incomplete sidewall fusion, or leaks. All of which can affect the strength and longevity of your welds. Borescopes increase efficiency and limit downtime. They help quickly and easily inspect welds and can offer full image and video and photo documentation.

The quality and color of a weld bead and any residual deposits can be visually inspected with color video scopes like the X1 Series. It’s coated insertion probes are designed to prevent polished pipes from surface scratches. Inspecting very small welded piping requires a flexible borescope. Because of their construction, sanitary piping or other high purity piping require a borescope capable of sharp bends and rotate 360° to view entire welds. For this, an articulating borescope with a flexible probe should be used.

Inspecting welds directly can reduce costs by detecting defects in earlier stages of manufacturing, reducing the cost of customer returns and extending the life of the components. A factor in making high-quality welds is cleanliness. Therefore, inspectors look for weld porosity or contamination in addition to other common weld faults. Standards for welding quality may differ from job to job, but the use of appropriate techniques can ensure the applicable standards are being met.