Visual Examination of Welds

The integrity of most welds is verified principally by visual examination. This inspection methodology constitutes an important practice in quality control. Visual examination is easy to apply, quick and requires no special equipment other than good eyesight.

The only limit to the extent of the defects detected by visual examination is the knowledge and experience of the inspector.

Contrary to popular belief, visual examination does not just happen during or after the welding activity. It should start even before the start of fabrication, even before the welder picks up and turns on his/her welding machine.

Pre-requisites to visual examination

1. Visual acuity - a documented periodic visual acuity exam is a requirement of many codes and specifications.
2. Equipment - some inspections may require tools or equipment and these must be properly calibrated prior to use.
3. Experience and Training - the inspector must have sufficient knowledge and skill to perform the examination.
4. Procedures - development of standardized procedures ensures consistency and accuracy.
5. Certification programs - several standards offer certification such as AWS QC1, Standard for Certification of Welding Inspectors.
6. Safety - last but not definitely not the least. All personnel working in a welding environment shall seek safety training.

Prior to Welding

1. Review drawings and specifications - information to gain here are the weld details, material requirements, inspection requirements, dimensions and qualification requirements.
2. Check procedure and performance qualifications - this is to ensure that the qualifications of both the weld and the welders meet the requirements of the code and the job specifications.
3. Establish Hold Points - hold point is where an examination is to occur prior the accomplishment of any further fabrication. It shall be reflected in the inspection and test plan as seen below where the inspector can comment on it prior the start of the inspection.

4. Establish documentation plan - this is to easily document inspection records which will be needed for final acceptance.

5. Review material documentation - verification if the correct material will be used for fabrication.

6. Examine base materials - base materials shall be free of discontinuities or defects as well such as cracks, laminations etc.

7. Examine joint fit-up and alignment - these are critical in ensuring a sound weld. If the fit-up is poor, it must be corrected prior welding.

8. Review storage of welding consumables - welding consumables such as electrodes, filler rods, etc. must be in accordance with manufacturer's recommendations. For example, these electrodes must be stored in an oven at a prescribed temperature.

During Welding

1. Check preheat and interpass temperatures - depending upon the code or contract documents these parameters are sometimes specified and must be checked with the right instrument as it can affect the weld quality. Insufficient preheat will result to rapid cooling and thus embrittlement will occur.

2. Check conformance with welding procedure specifications - the WPS must be the guiding document during welding, variables such as wire feed speed for GMAW, joint design, electrical characteristics and techniques must be verified.

3. Examine weld root pass - many defects are discovered in the weld root bead. In one of my projects, the radiographic examination detected a defect in the root pass which caused delays to the turnover of the project to operations. A good visual examination could have avoided it in my opinion.

4. Examine weld layers - though time consuming, this provides a check if cleaning is adequately done in each pass, this alleviates the occurrence of slad inclusions.

5. Examine second side prior welding - this applies to double-welded joint.

After Welding

1. Examine weld surface quality - weld concavity and convexity can be checked visually. Other workmanship issues such as weld spatter, arc strikes can also be checked. The following surface discontinuities can be checked as well:a. Porosityb. Incomplete fusionc. Incomplete joint penetrationd. Undercute. Underfillf. Overlapg. Cracksh. Metallic and nonmetallic inclusionsi. Excessive reinforcement
2. Verify weld dimensions - dimensional checks shall also be done to the weld in accordance to the approved drawings.
3. Review subsequent requirements - review the specification to determine if additional procedures are required such as NDE, PWHT etc. The inspector is responsible if these tests are conducted. If you want to know more about welding inspection and pass the CWI exam, I have a welding introductory course for the fundamentals part of the CWI just click the link here and it will take you to the course. If you love free stuff and want to know more, you can also check out my videos here regarding the fundamentals of WPS and PQR.