Most weld defects are decided long before the arc is struck and discovered long after it is extinguished. A joint can look perfect and still carry a flaw that began with the wrong consumable, a missing preheat or a welder qualified for a different position. That is why good welding inspection follows the work through three stages instead of waiting for the finished weld.
This article describes what an experienced welding inspector checks before, during and after welding, and why the order matters. It is aimed at buyers and quality managers who rely on welded fabrication from Indonesian yards and workshops, and who want to understand where inspection effort pays off and where it merely adds paperwork.
- Why three stages
- Before welding: documents and materials
- Before welding: joint preparation and fit-up
- During welding: parameters and discipline
- After welding: visual inspection and NDT
- Weld mapping: the backbone of traceability
- Conditions that matter in tropical and coastal yards
- Frequently asked questions
Why Three Stages
A finished weld is the least informative point to inspect. By then, the root is buried, the heat has done its work on the metal and the only evidence left of how it was made is the record. Checking a weld only at the end tests the outcome but not the process, and a process that was uncontrolled can produce flaws that surface methods will never show.
Inspecting in stages moves attention to where problems can still be prevented. Before welding, the inspector confirms that the right people, procedures and materials are in place. During welding, the inspector checks that the process is being followed. After welding, the inspector verifies the result and closes the record.
This approach is widely used in welding quality assurance, and quality requirements for fusion welding are often framed through standards in the ISO 3834 series. Whatever code applies, the logic stays the same: prevention first, detection second, documentation throughout.
Before Welding: Documents and Materials
The first checks are on paper. The inspector confirms that an approved welding procedure covers each joint, that the supporting qualification record exists and that every welder assigned holds a qualification valid for the process, material, thickness and position. Finding a mismatch after welding means cutting out and repeating the work, so this is the cheapest check on the job.
Materials come next. Plate, pipe and fittings should match the specified grade, and their markings should trace to the material certificates. Welding consumables must be the type and batch the procedure calls for. Mixing up two similar-looking electrodes or wires is a classic cause of failures that look unexplained until someone checks the packaging.
Handling and storage deserve attention too. Low-hydrogen electrodes and many fluxes need controlled storage, and the inspector checks that ovens, holding temperatures and issue procedures are respected. Equipment is part of the picture, as meters on welding machines should be calibrated if their readings are relied upon for parameter control.
Before Welding: Joint Preparation and Fit-Up
Fit-up is the last chance to inspect what the weld will cover. The inspector checks joint geometry against the drawing and procedure: bevel angle, root gap, root face, alignment and cleanliness. Moisture, oil, paint, rust and mill scale in the joint area are removed or controlled as the procedure requires.
Misalignment is a frequent trouble point. Too much high-low between members can prevent proper root fusion and put stress on the joint, and the acceptable limits depend on the code and the service. The inspector measures instead of estimating, and records the result against the specified tolerance.
Preheat requirements are verified at this stage as well. The inspector checks that the heating method is suitable, that the temperature is measured with a calibrated instrument at the right distance from the joint, and that readings are recorded. Because fit-up is usually the last time the joint can be seen, it is the natural hold point in a plan.
During Welding: Parameters and Discipline
Surveillance during welding verifies that the procedure is being followed. The inspector checks current, voltage and travel speed against the allowed ranges, along with the preheat and interpass temperatures. Heat input matters for toughness and strength in many steels, and drifting outside the range is a common reason welds later fail mechanical requirements.
The root pass is the most critical. It is difficult to inspect once covered, so many plans place a hold or witness point on it. The inspector looks at the bead shape, fusion at the sides and any signs of poor penetration or contamination, and confirms that cleaning between passes is carried out as required.
Discipline is also about people and materials. Each welder should be identifiable on the work, whether through a stamp or a recorded identification, and consumables should be issued and returned in a controlled way. Wind and drafts affect shielding in some processes, so protective screens and the control of the working environment are checked when conditions demand it.
After Welding: Visual Inspection and NDT
Visual inspection is the first step after welding and often the most valuable. The inspector examines the surface for cracks, undercut, overlap, excess or insufficient reinforcement, spatter, arc strikes and incomplete filling, and measures weld dimensions where required. Every other test is more efficient when visual inspection has already removed the obvious flaws.
Non-destructive testing follows according to the specification. Surface methods look for flaws open to the surface, while volumetric methods such as ultrasonic or radiographic testing examine the inside. The extent depends on the contract and the code. Timing can matter: some specifications require a waiting period before NDT on certain steels, to allow delayed cracking to appear.
Other checks may apply, including post-weld heat treatment records, hardness tests, dimensional checks and marking. If repairs are needed, the repair procedure, re-inspection and any additional NDT should be recorded as carefully as the original weld. Weld maps and records then close out the stage.
Weld Mapping: The Backbone of Traceability
Weld mapping assigns a unique identification to each joint and ties it to the information that describes it: the welder, the procedure, the consumable batch, the inspection results and any repairs. Industry standards such as ISO, ASME and AWS direct how such mapping is handled, and the practice is a core element of weld quality assurance, as the overview of weld quality assurance notes.
For buyers, the weld map is the most useful document in the data book. It answers questions that surface years later, such as which welder made a specific joint, which consumable batch it used and what NDT it passed. Without it, tracing a problem means re-inspecting everything.
A good map is built before welding starts and updated as work proceeds. If it is compiled at the end from memory and loose records, it becomes a reconstruction, and reconstructions invite doubt. Ask to see the map during fabrication, not only in the final documentation.
Conditions That Matter in Tropical and Coastal Yards
Yards in Indonesia often work in hot, humid, coastal air and sometimes in the open. Moisture pickup is a concern for some consumables and for surfaces that must be dry before welding, so storage discipline and the condition of the joint at the time of welding deserve extra attention.
Wind off the sea can interfere with gas shielding on open sites. Rain pauses work and can leave moisture in joints that were ready earlier in the day. Inspectors should check the protection arrangements, the drying of joints and whether the vendor has a clear rule for stopping work in bad conditions.
Many Indonesian vendors work with sub-contract welders who move between jobs. That makes the pre-welding check of qualifications especially important, because a certificate shown at the gate may not cover the position or material in the weld you care about. G.I Quality Services lists welding inspection among its QA/QC services, and any welding inspector appointed should be able to walk through these three stages for your own project.
Frequently Asked Questions
What does a welding inspector do?
A welding inspector verifies that welding is carried out and recorded according to the specified procedure and code. This includes checking documents and materials before welding, monitoring the process during welding and examining the finished weld and its records afterwards.
What are the stages of welding inspection?
The common stages are before welding, during welding and after welding. Before means qualifications, procedures, materials and fit-up. During means parameters and discipline. After means visual inspection, NDT, repairs and records.
Why is visual inspection done before other NDT?
Visual inspection is quick and cheap and removes obvious defects before more expensive tests are performed. Many codes treat it as the first examination, and it provides context that helps interpret later results.
What is weld mapping?
It is the practice of giving each weld a unique identification and linking it to the welder, procedure, consumable, inspection results and repairs, so that the history of every joint can be traced.
When should NDT be carried out after welding?
According to the specification and code. For some materials a waiting period is required before final NDT to allow for delayed cracking, so follow the requirement in the contract documents.
Who is responsible for weld quality, the welder or the inspector?
Responsibility for producing a sound weld lies with the fabricator and its welders. The inspector verifies conformity and reports, but does not take over the fabricator’s responsibility.