Making quality welds is necessary as both a hobbyist and a professional welder. However, the quality of the weld is far more important for professional welders or welds that need to be inspected by a Certified Welding Inspector.
Welding inspection is a critical aspect of the international welding trade as they provide a quality check to ensure that welding protocols are up to standards, and to verify the quality of the weld. As a professional, this means that your welds and weldments will be analyzed to a specific standard.
To improve your trade and your product quality, it’s important to understand what the welding inspector is looking for and how to improve your craft. Read on to learn more about welding quality for inspection standards.
What Does a Welding Inspector Do?
A welding inspector is a professional in the welding industry who holds national and international certifications to ensure welding quality. Welding inspector job roles generally include:
- Handling qualification records
- Overseeing non-destructive testing
- Ensuring proper materials are available during tests
- Ensure workplace safety
- Compliance under employer safety regulations, and local, state, and federal safety regulations
- Potentially developing an accredited testing facility’s quality control program
- Reviewing welding procedure specifications, building and welding plans, equipment calibration, and welding materials
- Inspecting pre-welding environment (including base and consumable materials) to check cutting methods, joint positions, welder settings, and clamp placement, for example
- Monitoring the welding process
- Inspecting welds
- Supervise repairs
As you can see, there are a number of things that the inspector is involved in that have to do with maintaining high-quality welds in the industry.
Common Weld Standards
Most testing standards in the U.S. fall under the ANSI Z49.1:2021, which is Safety in Welding, Cutting, and Allied Processes. This American National Standard covers all aspects of safety and health in the welding environment, emphasizing oxygen gas and arc welding processes with some coverage given to resistance and high energy beam welding, brazing, and soldering. It also contains information on the protection of personnel and the general area, ventilation, fire prevention and protection, and confined spaces.
This is a comprehensive standard that includes representatives from the major Welding organizations, including the American College of Occupational and Environmental Medicine, the American Welding Society, the Canadian Welding Bureau, International Safety Equipment Association INC, and the U.S. Departments of the Army, Navy, Air Force, and Public Health Service (NIOSH).
Welding Inspectors vs. Non-Destructive Welding Technicians
The quality of a weld is extremely important because poor quality can lead to safety hazards. Therefore, most welds need to be tested using a non-destructive welding test. Both welding inspectors and non-destructive welding technicians can test for this, but it’s important to understand the differences between the two occupations.
Common Welding Tests and Requirements
Inspectors will conduct examinations to ensure that welding processes follow safety codes, and to ensure that the weld itself meets the codes. Additionally, different standards apply based on the industry. For example, different weld standards are applied to welds on iron bridges compared to airplanes or aerospace welds.
The most common quality weld tests are non-destructive testing using Radiographic technology and non-destructive testing using ultrasonic testing. As we will get into below, both these methods test for and detect internal flaws and irregularities without destroying or affecting the integrity of the weld.
Non-destructive Weld Testing
The most common and important test for welding quality is a non-destructive test (NDT). NDT can be performed by both certified welding inspectors (CWI) and non-destructive welding technicians. NDT includes different methods for evaluating weld soundness. This requires that the part is tested without being destroyed in the examination process.
NDT methods make sure that the welds meet the relevant codes, contracts, and safety regulations, so specific methods might vary based on the region of the inspection and the overseeing inspection body. For example, the American Welding Society determines certain standards approved by the American National Standards Institue (ANSI) that their certified inspectors have to follow. Their standards abide by and regularly change with the state, federal, and local regulations related to the product, industry, and weld needs.
There are five main types of NDT welding inspections used in North America. These include:
- Visual inspection
- Radiographic (or X-ray)
- Ultrasonic
- Magnetic Particle
- Liquid penetrant
Each method of inspection will inform the inspector about the quality of the weld based on how it reacts or the data that comes from each inspection type. However, the type of inspection used will depend on the assets, tools, and technicians available.
Visual inspection
Visual inspection testing (VT) is the simplest NDT inspection where the inspector examines the weld visually to determine and spot surface flaws. The weld size can also determine possible issues.
This is the most cost-effective weld inspection type but it’s obviously very limited. A visual inspection may be conducted throughout the welding process, often by managers too, to ensure that no obvious defects exist.
Radiographic (or X-ray)
Radiographic or X-ray inspection (RT) will evaluate the internal quality of the weld to identify internal flaws, such as non-metallic inclusions, burn-through, and cracks. This method is recorded on film, which means that the inspection data can be used in a later examination as well. The quality of this inspection relies on the ability of the inspector, though, and not all welds work with this type of inspection.
Ultrasonic
Ultrasonic testing (UT) can identify both internal and surface flaws, including the location and measurement of the discontinuity. This method is very sensitive, which is good in that it can allow inspectors to find minor, and hard-to-spot imperfections that other NDT methods might miss.
Ultrasonic inspection uses phased array technology. The Phased Array Ultrasonic Testing is one example of ultrasonic testing, and this can evaluate a weld from multiple angles. Advanced ultrasonic testing might use technologies such as Total Focusing Method (FDM) or Laser-Induced Breakdown Spectroscopy (LIBS) to measure the Lithium, Boron, Carbon, and Beryllium in produces.
Magnetic Particle
Magnetic particle inspection (MT) spots surface and near-surface flaws. This method will identify defects immediately, but you can also adjust the sensitivity to detect various levels of flaw detection. Therefore, this method can spot both minor imperfections, cracks, and discontinuities.
Magnetic particle testing can only be used on ferromagnetic materials (i.e., iron and steel). So you cannot use this method on magnetic materials or materials with thick paint applications.
Liquid penetrant
Liquid penetrant inspection (PT) is a form of testing that identifies surface cracks invisible to the naked eye. This method will commonly spot leaks due to welding flaws. PT can be used to evaluate magnetic and nonmagnetic materials, and it can also be used to spot flaws in complex shapes. This is still limiting on its own, as only surface flaws can be detected.
Preparing for a Weld Inspection
What Does a Welding Inspector Look For?
Welding inspectors will come in and test the quality of the weld with their method of NDT. As a certified welding inspector or quality inspector within your industry, they will also ensure that:
- The weld quality stands up to the applicable standards
- The weld protocol has been followed
- Safety requirements have been followed
- The welded product will not break down upon repeated use and over time
- That the welded product passes the applicable NDT test and contains an appropriate level of imperfections internally and externally
The welder looks at more than just your weld quality. There are other code requirements as well.
What are the Three Stages of Welding Inspection?
There are three stages of a welding inspection:
Stage 1: The welding inspection prior to welding work
Stage 2: Welding inspection during welding
Stage 3: Welding Inspection upon completion of the weld
What Should I Expect in Stage 1 of the Welding Inspection?
Stage one includes a pre-weld inspection. Here are some of the things that your inspector will be looking for:
- Proper documentation of things like your welding symbols, welding sizes, weld joint designs and dimensions, specific weld joints, base material requirements, and the proper handling of consumables.
- Definitions of safety requirements, such as weather protection, windbreak, preheat requirements, post-weld heat treatment, and hold points.
- You’ll also need to specify testing requirements, such as mechanical properties, pressure testing, and competency.
- The inspector will want to know that your organization is prepared according to welding standards, which includes defining roles of engineers, keeping records, ensuring welder performance qualifications meet standards, and more.
- NDT preparation is also important. Be sure you are prepared with the NDT technique and procedures.
- You’ll have to prepare your equipment for testing, calibration, and necessary recording. Calibrate your equipment, including NDT equipment, welding machine, and instruments, including voltmeters, contact pyrometers, and ammeters. The inspector may need to use or test the storage oven, so make sure that all your equipment is in order. Prepare for heat treatment, pressure testing, and PWHT equipment calibration. Material test certifications are available and marked.
- You’ll want to confirm all your materials, including filler materials, are up to certification and that traceability information is performed.
There are other extra checks that you’ll have to move through before the test occurs. In the test, you’ll want to make sure that the weld joint, materials, and workspace are free from contaminants and that the welds are tested properly. Inspectors will monitor alignment, dimensions, proper preheat, reheat, and proper technique. Be sure to check on the gas requirements as well.
What Should I Expect in Stage 2 of the Welding Inspection?
Stage 2 is the welding inspection itself. This is the most intensive part of the inspection because it requires the inspector to watch a qualified welder complete the official welding process in real-time. This means that the welder may need to demonstrate verbally everything they are doing, why, and what the standard is.
They’ll want to test the welder’s understanding of welding procedures, special training, inspection hold-points, essential variables (EVs), filler material, fluxes, inert gas composition and flow rate, purge technique, flow rate, O2 analysis, rod warmers, preheating, welding technique, weld progression, bead overlap, equipment settings, interpass temperatures, travel speed, heat input, mock-up weldment, tack welds, adequate weld root, cleaning between weld passes, and other best practices.
The inspector will watch the welder’s in-process rework and defect removal, in-process ferrite measurement, and final weld reinforcement, and ensure the fillet weld size meets work specifications and drawings.
What Should I Expect in Stage 3 of the Welding Inspection?
After the in-progress weld inspection (stage 2) is complete, you’ll have to complete stage 3. In stage 3, the inspector checks the weld quality, application, and follow-up procedures.
With the weld quality, the inspector will check:
- That the size, length, and location of all welds conform to the drawings, specifications, and Code
- That no welds were added without approval.
- Using dimensional and visual checks, the weld doesn’t have discontinuities, excessive distortion, and poor workmanship.
- That any temporary attachments and attachment welds were removed and blended with the base metal.
- Discontinuities reviewed against acceptance criteria for defect classification.
The inspector will also want to ensure the PMI of the weld, welder stamping, hardness. They will check NDE after a final hardness check. Other factors of the weld inspected include: RT film quality, IQI placement, IQI visibility, and more complying with standards.
Once the weld inspection is completed, the welder should properly shut down the equipment internals and properly fasten thermocouples. Other shut-down procedures will need to be followed, as is usual in welding shut-down.
A final visual examination and audit are completed to identify inaccuracies and to make sure that the quality plan was properly executed.
What are Important Requirements About the Inspection found in ASME Section IX?
In addition to the three stages of the welding inspection, companies and professional welders need to also abide by the requirements found in the ASME section IX. Inspectors will be checking each of these things, so make sure you have them:
- The company must have a WPS or a written document that provides direction to the welder professional for making a production weld according to the code. You must also have your PQR documents. Here’s more info on the WPS and PQR.
- Welders must demonstrate proper procedure and performance qualifications. Procedure qualifications give suitability of weld for required mechanical properties (i.e., strength, ductility), while performance qualifications show the ability of the welder to deposit a sound weld. You must also keep a record of the results of these qualifications.
- Procedure Qualification: Tension test + Bend test
- The tension test gives tensile value, while the bend test shows ductility and soundness.
- Tensile test for procedure qualification is passed if failure is in a)Weld metal at strength>= Base metal SMTS or b) Base metal at strength>= 95% of base metal SMTS. This must be checked by a welding inspection company.
- Performance Qualification: Bend test or Radiography
- Bend test crack shall not exceed 1/8” in any direction. Radiography also indicates soundness. Radiography criteria are stricter than radiography for the job and can only be used for SMAW, SAW, GTAW, PAW, and GMAW (except short-circuiting).
- If you fail the visual examination, you can do an immediate retest and will need to do two retests.
- For welder performance qualification by radiography for an immediate retest, two 6 inch plates and pipe examinations shall include two pipes for a total of 12 inch of weld which shall include the entire weld circumference.
- For performance, 1G is flat, 2G is horizontal, 3G is vertical, and 4G is the overhead position. Pipe 5G qualifies 1G, 3G, and 4G, but pipe 6G qualifies all positions.
- Procedure Qualification: Tension test + Bend test
- The test will classify the metal classification related to the test properties (i.e., similar strength and ductility), the usability of filler material, chemical composition, and variables that can or cannot be changed depending on the procedure qualification. For example, some variables will be considered essential if they impacted strength. If you removed that item it might decrease the strength of the weld and weaken the weld. These classifications are included in your inspection documents.
- When the welder has not welded with a process during a period of 6 months or more, his qualification for that process shall expire.
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