Welding inspections are necessary to check the quality of the weld. In evaluating the quality of a weld, there must be some criteria to which the weld characteristics can be compared. There are stages of some weld discontinuities that can be accepted depending on the suitable quality for its intended application.
The acceptance criteria for the quality of welding can originate from several sources. The sizes and some other dimensional information such as the length and locations of welds will be provided in the welding fabrication drawing or blueprint.
These requirements are created through design calculations or obtained from proven designs that meet the quality of the welded connection. Well, in this reading, we’ll explore what welding inspection is, and who is a welding inspector. We’ll also explore the techniques and advantages of welding inspection.
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What is Welding Inspection?
Weld inspection involves trained specialists conducting proper inspections of welds for quality, strength, and safety. These inspections ensure the fabrication is safe and secure, ensuring the safety of both workers and civilians. Welds, made of metal, thermoplastics, or other materials, are used in various industries worldwide, making proper inspection crucial for maintaining safety.
Welding inspection is to check or know characteristics a weld has and to inspect discontinuities in the weld. The size of a weld is very important as its strength and performance can be determined. It is good to know the performance of a weld and to know if it may or may not withstand stresses applied during service.
The primary purpose of weld inspection is to reveal the weld quality and discontinuities in the weld, knowing if the objectives are met. Discontinuities are known as welding defects, and they cause premature weld failure due to added stress concentrations or reduction of strength within the welded component.
Who is a Welding Inspector?
A welding inspector is a qualified person who detects a weld to ensure it meets the code and standard requirements. As welding inspection requires a wide variety of knowledge, a welding inspector to have an understanding of welding and fabrication entirely including the reading of welding drawings, symbols, and procedures; welding joint design; code and standard requirements; and inspection and testing techniques.
Welding inspectors must undergo welding inspection training and ensure they obtain certification by passing the examination. There are a number of training courses available internationally, but the most popular program used in the USA is administered by the American welding society (AWS).
Related: 13 Types of Welding Defects, Their Causes and Remedies
Stages of Weld Inspection
Weld inspection is a crucial process that involves three stages: pre-weld inspection, during-weld inspection, and after-weld inspection.
Pre-weld inspection involves tasks such as ensuring safety measures are followed, understanding the job, gathering materials, and preparing tools or energy sources. During-weld inspection involves tracking heat input, cleaning between passes, monitoring welding technique, and identifying visual signs of problems.
After-weld inspection occurs after the weld has cooled and fused, checking for adequate weld size, identifying discontinuities or flaws, ensuring product meets specifications, and testing weld strength. Proper weld inspection techniques can be deployed at every stage of the welding process, with each having its specific use case and application
Destructive and Non-Destructive Weld Inspection
Destructive weld testing is a process that involves breaking off a welded piece to examine its mechanical and internal physical traits. This inspection can be performed for various reasons, such as weld failure analysis, research, sampling inspection, or certification training. Non-destructive weld inspections involve visually examining the weld or its interior without breaking any pieces of the fabrication.
Destructive weld inspections destroy the weld to ascertain important information. Both types of inspections are usually performed after the weld is complete. Non-destructive weld inspections aim to find discontinuities without altering or destroying the finished piece. They vary in application, price, and operator knowledge, and may be performed by the welder themselves.
Both types of inspections are essential for ensuring the final weld is safe, secure, and strong.
What are the Types of Weld Inspection?
The welding inspection techniques are visual inspection, surface crack detection, radiographic and ultrasonic weld inspection, destructive weld testing, and sound welding inspection. These welding inspections are categorise into destructive and non-destructive inspections.
1. Visual Inspection
Visual inspections are a common method used by welding technicians to detect any noticeable discontinuities in slag. These inspections are quick, inexpensive, and easy to perform on all gear and materials. However, they cannot identify internal discontinues like porosity or slag inclusions due to the fallibility of human eyesight.
2. Surface Crack Detection
Weld inspection, also known as dye penetrant testing, is a method used to identify microscopic cracks on the weld surface that may be invisible to the naked eye. This process involves spreading a brightly colored or fluorescent dye across the weld surface, allowing it to dry. Surface crack detection, similar to visual inspection, identifies surface flaws but cannot identify internal weld failure.
3. Radiographic Weld Inspection
Radiographic weld inspection uses medical X-rays to detect discontinuities and faults within a part’s internal structure. This process, similar to medical X-rays on the human body, displays variations in shape and color on photographic film.
These variations can indicate weld discontinuities like slag inclusion, porosity, and cracks. However, like medical radiographs, there are health and safety risks, and only trained professionals should perform this type of weld inspection.
4. Ultrasonic Weld Inspection
Ultrasonic testing involves beaming a high-powered mechanical frequency into a weld piece, which is then reflected back to a transducer. This reflected signal helps determine the size, shape, and nature of weld failure. This non-destructive method is effective in determining internal discontinuities, but requires operator knowledge and expensive equipment. The reflected signal can be measured in various ways.
5. Magnetic Particle Weld Inspection
Magnetic probes are used in the Magnetic Particle Weld Inspection method, which involves applying probes to the surface of a weld. The accumulation of particles at the magnet ends can indicate weld discontinuities. If no particles accumulate, cracks are likely. This non-destructive inspection method is effective on specific materials and circumstances, but requires specific probes and materials.
6. Sound welding inspection
This is one of the most successful welding quality inspections. It should be after the evaluation of the full weld quality requirements and acceptance criteria.
7. Macro etch Weld Inspection
The etch process is a vital part of the inspection process, providing a visual snapshot of the internal structure of a welded joint. This process involves carefully polishing small samples from the welded joint, which are then etched at their center using a mild acid mixture, ensuring a thorough examination.
8. Transverse Tension Weld Inspection
This weld inspection involves determining the tension per unit in a cross-sectional area of a welded piece. Transverse tension weld inspection involves pushing a specimen to failure, dividing the maximum load required by the cross-sectional area. This method helps determine limits and minimum requirements when working with new or different materials, ensuring the safety of the welded piece.
9. Guided Bend Test Weld Inspection
Welded joints are tested for their ductility and structural integrity through guided bend tests on a weld part. These destructive inspection methods evaluate the ductility and integrity of certain kinds of welded joints. Various types of bend tests are commonly used in training and qualification tests to ensure welders are prepared for real-world practice.
Things to Checkout for During Weld Inspection
A weld inspection is a crucial step in the welding process, ensuring the safety and quality of the job. It involves a thorough review of blueprints and drawings, ensuring all materials are specified in the schematics, and checking the physical condition of the materials to be welded.
The welder must also ensure the workspace, tools, and welding materials are clean, calibrate them as needed, and verify their qualifications and certification for the job. The welder must also preheat the energy source before starting the welding process.
The inspection checklist involves monitoring heat, voltage, technique, and temperature, if applicable, to ensure safety precautions are followed. Visually checking individual weld passes and identifying potential problems is crucial. After-weld inspections, including post-heat treatment, are also performed to ensure weld length and size are checked.
Related: 15 Different Types of Welding and Their Uses
Equipment Used In Welding Inspection
Weld inspection equipment is essential for ensuring safety during the welding process. Different tools may be needed depending on the location of the weld and the inspection. Common weld inspection equipment includes a borescope, bridge cam, codes, weld signs, flashlight, high-low gauge, pit gauge, log book, mirror, owner specifications and drawing, personal protective equipment, and a radiograph machine.
Drones, or uncrewed aerial vehicles, are another crucial piece of weld inspection equipment. Ideally, the majority of weld inspection should occur before the welded piece leaves the shop. However, annual inspections and safety regulations may require examination of hard-to-reach places like oil tanks, hangars, and mines.
Drones equipped with ultrasonic can increase accuracy and safety during weld inspection. Overall, protective equipment and drones are essential tools for maintaining safety during the welding process.
What are the Advantages of Welding Inspections?
Weld inspection is a crucial process that ensures safety during the welding process, identifying and addressing any weld discontinuities before a piece leaves the shop or factory. It is essential to maintain regulatory compliance and protect civilians by preventing faulty products from entering public use.
Annual inspections of welds experiencing high stress are also part of a comprehensive safety protocol. Weld inspectors help workers avoid inherent dangers, such as burns or eye damage, by ensuring proper precautions are taken. Welders typically wear personal protective equipment to minimize exposure to these hazards.
Weld inspectors play a crucial role in ensuring safety in the workplace by adhering to strict safety procedures and preventing the inhalation of dangerous gasses. They are formally qualified by the American Welding Society or another certifying board, ensuring that workers follow regulations and prevent faulty products from entering the public sphere. Their goal is to prevent safety issues before they occur.