If you are a new welding engineer or inspector, there are many fine points and insights in the construction sector. The following list contains methods that are used during the execution process as well as after completion to inspect welding projects. With the exception of Charpy and Destructive testing, the remainder are all Non-Destructive Testing or NDT methods such as Charpy V notch testing, Destructive Testing, Visual Inspection, Hardness testing, Ultrasonic testing, Eddy-Current Testing, Radiography, Liquid-Penetrant testing, and Magnetic Particle testing.
Type of Weld Inspection and Their Application
1 – Visual Inspection
This is the least expensive, simplest, and easiest method using the human eye and a few tools plus it is the most effective of the welding inspection methods. This method is done in a workshop or field while the welding is being done. The things that are visually checked include the welder’s certificate, slag removal, joint preparation, weather conditions, current used, and condition of the electrode.
2- Magnetic Particle Testing
This test is used to find any surface or barely subsurface defects in a weld. This test is accomplished by passing an electric current through a weld so that a magnetic field is formed. Particles of iron are then applied to the magnetic field and if there are any defects, the particles of iron will build up around the defect, which shows where the defect is and why it happened.
3 – Liquid-Penetrant Testing
This test will detect defects in the surface of the weld like porosity and hairline cracks. This test is accomplished by the use of a liquid penetrant that is applied to the surface of the weld. A developer is then applied that will show if any defects are visible.
4 – Ultrasonic Testing
This test is accomplished by the use of sound vibrations, which are then transmitted through the welded joint. The signals received on a glass screen will determine if there are any defects in the joint of the weld. Other detectable things an ultrasound test can find are how thick the joint weld is, blowholes, lack of penetration, and cracking.
5 – Eddy Current Testing
This test will show extremely small cracks and is accomplished by the use of a circular coil that carries alternating currents, which is placed near the weld. The alternating currents will create a magnetic field, which will interact with the weld and in turn, generate an eddy current. If there is a flaw present, there will be a change in the eddy current, which will be measured by a receiver coil.
6 – Radiography
Also called the X-Ray method (electric source) and Gamma-Ray method (radioactive source), it is a non-destructive testing process that is used to check the internal structure of welds. A film is produced by using an iridium isotope that passes through the weld. The things that are inspected by using this method are porosity, material inclusion, lack of fusion, cracks, excessive penetration, and concavity.
7 – Hardness Test
This method is accomplished by hitting a specific load on the indicator that is placed on the weld. The resulting indentation size is referred to as a hardness measuring table.
8 – Destructive Testing
This test is a destructive test that is accomplished by cutting the completed weld into pieces, this is per the code for root bend, face bend, tensile test, and side bend. It is used to locate slag inclusion, porosity, and undercutting defects in welds and is very effective.