Visual Inspection (VT)

Visual Inspection (VT)

Since the welding inspector’s responsibilities can be extensive and will occur at various stages of the fabrication sequence, a helpful aid is an “inspection checklist.” 

Such a document will help the welding inspector organize the inspection effort and assure each specific task has been performed. 

An example of such a listing is shown in Figure Also, the various tools used by the visual welding inspector will be reviewed. While the visual inspection method is characterized as requiring a minimum of tools, there are certain devices which can help the welding inspector perform more easily and effectively. 

Figure illustrates some of these tools which might be used by the welding inspector to aid in evaluating welds and weldments.

It has been mentioned that the only way in which visual inspection can be considered to effectively evaluate the quality of welds is to apply that inspection at every step of the fabrication process.

Unless there is an ongoing program, certain discontinuities could be missed. Further, the main reason to perform the inspection on a continuing basis is to discover problems as soon after they occur as possible so they can be corrected most efficiently.

Therefore, this discussion of the welding inspector’s “visual inspection” duties will be organized in terms of those tasks which are performed before, during, and after welding.

In some respects the responsibilities of the welding inspector prior to the start of welding may be the most important. It can at least be said that unless

this aspect of the inspection job is performed satisfactorily, there may be problems encountered later in the fabrication process.

Many of these tasks apply to the organization of the inspection which will follow, including becoming familiar with welding requirements, determining when inspections are to be performed, and developing systems for reporting and maintaining inspection information.

One of the first duties of the welding inspector at the onset of a new job is to review all of the documentation relating to the actual welding which is to be performed.

Some of the documents which may be reviewed include drawings, codes, specifications, procedures, etc.

These documents contain information which is very valuable to the welding inspector.

In essence, they describe what, when, where, and how inspection is to be performed.

Therefore, they provide ground rules for all of the inspections which will follow. This will help the welding inspector plan how to proceed in evaluating the welding to assure that it complies with job requirements.

Some of the information gained from this review of documents refers to the materials to be used for the welded fabrication.

Depending upon the type of material specified, there may be special requirements for its fabrication.

For example, if a quenched and tempered steel is specified, there will usually be a need for welding heat input control.

So,the welding inspector will be required to monitor the welding with this in mind.

Another preliminary step related to the materials being used is to check whether or not there are welding procedures which cover the required welding.

In addition to the types of materials beingwelded, the welding inspector must check if the qualified welding procedures provide adequate coverage with regard to welding process(es), technique, filler metal type, position, etc.

If some aspect of the upcoming production welding is not properly covered by the existing welding procedures, then new procedures must be developed and qualified in accordance with the appropriate code.

The welding inspector may also be responsible for the monitoring, testing, evaluation, and recording of those welding procedure qualifications.

Once all of the appropriate welding procedureshave been qualified, it is then necessary to review the certification papers of the individual welders to assure they are considered to be qualified and certified to perform the production welding in accordance with the approved welding procedures.

Some of the specific limitations relating to the individualwelder qualification include materials being welded,process(es), position, technique, joint configuration,etc. 

Those welders who do not have the proper qualification and certification must then be tested to assure that they are capable of performing production welding in accordance with the applicable procedures.

It is often helpful for the welding inspector if there is a listing of all of the production welders showing those procedures which they are considered qualified to perform. Further, some codes require that the welders permanently identify all of the production welds they have made. If this is the case, there should be an accompanying log showing the appropriate identification stamp of each welder.

There may also be a code requirement relating to the period of effectiveness of a welder’s qualification.

In such cases, a running log should be maintained and available for the welding inspector to review to determine if an individual welder has used a particular procedure within the specified time period. 

If not, the welder may require requalification.

Once the welding inspector has reviewed the appropriate documents related to the specific inspection job, he or she may elect to establish hold points. 

These are simply preselected steps in the fabrication sequence when the work must stop until the inspector has a chance to review the work completedto that point. 

Fabrication cannot continue until the welding inspector has approved the work up to that stage of the operation. This allows the work to be accepted on a step-by-step basis instead of waiting until the entire structure or component is completed. 

In that way, problems can be located and corrected with relatively little effect on the fabrication schedule. 

This also reduces the possibility that some minor problem which occurs at some early step will result in a major defect later in the fabrication sequence.

Another important preliminary step for the welding inspector is to develop a suitable plan for performing the inspections and recording and maintaining the results. 

Through experience, the welding inspector becomes more aware of how important this step can be. 

The inspector must know when a particular inspection task is to be performed and how it will be accomplished. There must be a plan so that important aspects of the fabrication process are not left uninspected. 

In general, the inspector can base this system on the basic steps of the fabrication process, so the inspection plan might simply use the production schedule as an outline for when a particular inspection step will be performed.

Once an inspection has been performed, there must be a suitable system established for the recording of the inspection results. 

This system should include provisions for the types and contents of' reports, the distribution of those reports, as well as some method of logically maintaining the records so that they can be retrieved and reviewed by others familiar with the job. 

Basically, the reports, and the system developed to maintain those reports, should be as simple as possible while still providing adequate information which is understandable to all personnel involved at some future review.

Another related matter involves the identification and treatment of rejects. 

At the beginning of every job, the welding inspector must establish some system whereby a rejected weld can be reported and identified. 

This system should include provisions for marking the location of a reject so that the production personnel understand the nature and location of the defect to enable them to easily find and repair the existing problem. 

There should also be some established convention regarding the reporting of that reject so that all involved individuals know that a defect exists and must be corrected. 

The marking used to indicate the presence and location of a defect should be some unique type or color so that it is clearly visible and descriptive to both quality control and production personnel. 

Finally, the system should describe how the reinspection after repair will be initiated and performed. 

Once performed, the method of reporting the results should be established so that the original rejection report is accompanied by a subsequent acceptance report.

The condition of the welding equipment to be used will also have an effect on the resulting weld quality. 

Consequently, the welding inspector should evaluate the performance and condition of the equipment. 

This includes welding power sources, wire feeding equipment, ground cables and clamps, flux and electrode storage devices, gas shielding hoses and accessories, etc. 

When evaluating the welding power sources, the accuracy of the equipment meters should be checked using calibrated voltmeters and ammeters so the welding parameters can be accurately determined during the production welding. 

Due to the inherent inaccuracies of some of these equipment meters, this can be an important step toward alleviating welding problems.

Once all of these tasks have been performed, it is now time to perform some preweld inspection of the materials and their configurations. 

One of these steps is to evaluate the quality of the base materials and welding filler materials. 

If problems exist in either of these items, they will likely create additional problems later in the fabrication sequence. 

If not discovered early enough, a material problem can be extremely costly when one considers the costs associated with the application of additional fabrication steps. 

So, it is extremely important that these problems are found before a great deal of time and materials have been applied. 

An example would be the presence of a lamination in a structural member.

If not discovered until all the cutting, drilling, punching, and welding have been performed, the costs of those operations cannot usually be recovered.

The supplier may have to simply replace the defective member, and the fabrication begins again from the start.

The inspection of the base materials will vary from simple visual inspection of the metal's surface to an elaborate combination of various nondestructive test methods to evaluate both the surface and subsurface quality of the material. 

The criticality of the structure or component will dictate to a certain degree the extent of inspection required.



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