Duties of a Welding Inspector 1

INTRODUCTION

INTRODUCTION

This is a description of what a welding inspector is, what he does, who he works with, and what his responsibilities are. The inspector should have knowledge on metallurgy, welding processes, welding qualification, welding symbols, weld discontinuities, control of material, nondestructive examination, and destructive testing so that he is aware of the variables that affect the quality of the weld and is aware of the methods used to verify the acceptability of the weld. This module describes the inspections that are performed by an experienced and knowledgeable welding inspector to obtain a high level of confidence that the final welded product conforms to the requirements of the technical specification, procedures, and the applicable codes and standard. These inspections are performed prior to welding, during welding, and upon the completion of welding.

As a welding inspector, you are not expected to perform all of the inspections described in this module. In addition, the frequency with which these inspections are performed may vary from surveillance inspection to full inspection of each weld. As a welding inspector, you are responsible to consult the technical specification, procedures, instructions, and the quality assurance or quality control manual for the inspections and acceptance criteria that apply for your specific application. Remember: The more inspections you perform prior to, during, and after welding, the greater will be your confidence that the welded product meets the requirements of the specification, procedure, and the applicable code or standard.

Preweld Inspection

In order to obtain a high level of confidence that the final weld meets specification, procedure, and code requirements, it is necessary to perform a number of inspections prior to welding. If the preweld conditions do not meet specification, procedure, and code requirements, there is a very high likelihood that the final weld will not be acceptable. By finding any problems before welding begins, corrections can be made with a minimum impact on cost and schedule. This can result in a significant savings by avoiding costly and timeconsuming rework, repair, or rejection of the product being welded.

Welding Procedure

A welding inspector is responsible for verifying that the welding procedure that is to be used has been approved for that specific weld joint by a responsible individual within the company's engineering group. Usually, this approval is obtained by identifying the welding procedure on a drawing or in a specification. This drawing or specification is usually signed by the project engineer or manager of engineering. However, in some companies, approval by other individuals such as the welding engineer may be acceptable.

The welding inspector should verify that the welding procedure that is to be used is complete, is approved by the required individuals, and has been qualified by testing, when required.

Material Conformance

In order to assure that the weld will be sound and have the required strength, the welding inspector verifies that the base metals, welding filler metals and welding gases that are to be used are properly identified and are in conformance with procedure and specification requirements. In addition, the welding inspector verifies that there are no unacceptable discontinuities in the base metal in the vicinity of the weld end preparation. The remainder of the base metal is usually inspected for discontinuities upon receiving or at the final inspection of the welded product.

Edge Preparation and Fitup

The welding inspector inspects the weld end preparation to verify that it meets the requirements of the welding procedure. This includes the bevel angle, root face dimension, depth of counterbore, and I.D. and O.D. transition, when required. The welding inspector should also verify that the minimum wall thickness at the weld is not encroached upon.

The cleanliness of the base metal on both sides of the joint is inspected to verify that it meets procedure and specification requirements. This includes checking for moisture; contaminants such as grease, oil, lubricants, and paint; scale; and corrosion products such as rust.

The welding inspector also verifies that the weld joint fitup meets procedure and specification requirements. This includes checking the root opening and the amount of mismatch (e.g., highlow). For structural steel welding to AWS D1.1 and other welding applications, it is often necessary to measure the root opening in fillet welds to verify that the final weld size has been increased above the minimum size by the amount of the root opening. Also, it may be desirable to measure the dimensions of the assembly prior to welding, especially where weld distortion is likely to occur.

Tack welds are inspected prior to welding to verify that they are adequate to avoid distortion during welding, are not cracked, and are adequately prepared to obtain complete fusion.

Edge Preparation and Fitup

The welding inspector inspects the weld end preparation to verify that it meets the requirements of the welding procedure. This includes the bevel angle, root face dimension, depth of counterbore, and I.D. and O.D. transition, when required. The welding inspector should also verify that the minimum wall thickness at the weld is not encroached upon.

The cleanliness of the base metal on both sides of the joint is inspected to verify that it meets procedure and specification requirements. This includes checking for moisture; contaminants such as grease, oil, lubricants, and paint; scale; and corrosion products such as rust.

Welding Equipment

The welding inspector should check to see that the welding equipment is properly set up and is in acceptable working order. This includes power supplies, lead connections, wire feeders, torches, and flow meters.

Purge

When a back purge is required, the welding inspector verifies that it is acceptable prior to welding. This may be based on the number of volume changes of gas based on the flow rate, pipe diameter, and distance between purge dams, or it may be based on measuring the oxygen content with an oxygen analyzer.

Preheat

The welding inspector verifies that the minimum required preheat is obtained prior to welding. This may be based on measuring the temperature of the base metal immediately adjacent to the weld groove with a temperatureindicating crayon, contact pyrometer, or other measuring devices.

Pre Heat Temperature Indicating Crayon

Welder Qualification

The welding inspector checks to see that the welder is qualified to make the specific weld. Variables to be checked include the welding process, base metal thickness, welding filler material, and welding position.

In Process Weld Inspection

The same reasons for performing preweld inspections also apply for performing inprocess inspections. Only by inspecting the welding while it is being performed can the welding inspector obtain a high level of confidence that the final welded product will conform to specification, procedure, and code requirements.

Welding Technique

The welding inspector verifies that the welding technique for the various passes conforms to the procedure and specification requirements. This includes the required use of stringer beads and limitations on the width of weave passes. This also includes any limitations on the thickness of individual passes. The welding inspector also verifies that the specified weld sequence is followed. Conformance to the required weld sequence is required in order to avoid distortion, excessive stresses, or cracking. Except for singlepass welds, the welding technique cannot be verified on final inspection.

Weave Bead Stinger Bead

Shielding

The welding inspector verifies that the type or mixture of shielding gas, the flow rate, and the amount of coverage meets the requirements of the welding procedure.

Interpass Cleaning

The welding inspector verifies that the cleaning between weld passes conforms to the requirements of the welding procedure. When back gouging and welding from the second side is required, the welding inspector verifies that the weld is gouged to sound metal on the backside of the first pass prior to welding on the second side.

Back gouging

Preheat and Interpass Temperature

The welding inspector verifies that the minimum required preheat is maintained during all welding operations. This is necessary in order to assure that the required mechanical properties are met, and that underbead or cold cracking will not occur.

The welding inspector verifies that the maximum interpass temperature is not exceeded. For austenitic stainless steels, a maximum interpass temperature is usually specified in order to minimize or avoid sensitization. Sensitization in austenitic stainless steel can lead to failures in service due to intergranular corrosion or stresscorrosion crackings.

Welding Variables

The welding inspector verifies that the welding variables, including volts, amps, and travel speed, conform to the requirements of the welding procedure. For manual and semiautomatic welding, the voltage is primarily a function of the arc length and, as such, need not be measured. The amperage is usually measured with a portable tong tester near the electrode.

Repair Welding

The welding inspector is usually involved in witnessing repair welding. This includes base metal repairs and repair of weld metal defects. The welding inspector is involved to assure that the unacceptable discontinuity is removed, and that the repair welding procedures are followed. Repair welds are usually more difficult to make than the original weld due to the size and shape of the excavation. The weld reject rate for repair welds is usually higher than for original welds.

Postheat

In some applications, the welding procedure or technical specification requires that the minimum preheat temperature be maintained after welding for a required length of time. This is done to diffuse hydrogen from the weld to avoid underbead, cold, or delayed cracking. The welding inspector verifies that this postheat is applied for the specified length of time, when required.

Cleaning

The welding inspector verifies that the weld is adequately cleaned prior to performing visual inspection. The inspector cannot perform his visual inspection if there is weld slag or if the weld is painted. Also, the welding inspector verifies that the weld is adequately prepared for the nondestructive examinations that are to be performed. The welding inspector is to be careful not to require excessive grinding, as such grinding is costly and time consuming.

Visual Inspection

The welding inspector inspects the weld for conformance to the weld size, length, and location specified on the drawing. For fillet welds, this includes measuring each leg and the throat dimension, the length, and the distancebetween the welds for intermittent fillet welds. The welding inspector also inspects the welded assembly for conformance to the dimensions specified on the drawing.

The welding inspector inspects the weld reinforcement, concavity, and surface finish for conformance to procedure and specification requirements. In addition, the welding inspector inspects for discontinuities such as undercut, underfill, cracks, overlap, incomplete fusion, incomplete penetration, porosity, and arc strikes. The acceptance criteria shall be in accordance with the procedure, specification, and the applicable code or standard.

The welding inspector inspects for special conditions such as oxidation, discoloration, and corrosion in certain materials that may be indicative of a fundamental welding problem.

Arc Strikes

Nondestructive Testing

The welding inspector often performs such nondestructive tests as examination by liquid penetrant testing, magnetic particle testing, radiographic testing, and eddy current testing. These nondestructive tests will find the types of discontinuities that are found by each method. When the nondestructive tests are performed by a subcontractor, the welding inspector is often responsible for monitoring the performance of the nondestructive test, reviewing the results of the nondestructive test, and indicating acceptance or rejection of the weld after reviewing the results.

NDT of aircraft engine

Destructive Tests

The welding inspector often performs one or more of the destructive tests. When the destructive tests are performed by subcontractors, the welding inspector often monitors and witnesses the performance of the test and reviews the results.

Tensile test machine

Postweld Heat TreatmentThe welding inspector verifies that postweld heat treatment, when performed, conforms to procedure, specification, and code requirements. This consists of monitoring and witnessing the performance of the postweld heat treatment and the review of the timetemperature recording chart. The postweld heattreatment records, including the timetemperature chart, should identify the weld, part, or assembly being postweld heattreated; the number and location of thermocouples; the time that the postweld heat treatment started and was completed; the heating and cooling rate; the holding temperature and the time at temperature.

Weld Identification

When required by the procedure, specification, or the code, the welding inspector verifies that the identification of each welder or welding operator who welded on the joint is stamped or etched adjacent to the weld or is identified on records traceable to the weld. The welding inspector identifies the status of his inspections by marking the material in the area of the weld or on records traceable to the weld. He is careful to use only approved marking materials that will not contaminate the material, especially on austenitic stainless steels and nickelbase alloys.

The welding inspector performs his inspections in a timely manner so as not to cause unnecessary delays in construction or fabrication. The welding inspector works to notify the foreman or superintendent of the status of his inspections so that any repairs can be made without unnecessary delays.

Welding Documentation

As a welding inspector, it is important that you document the inspections that are performed and that you prepare your report in a clear, concise, and accurate manner. If the acceptability of a weld is questioned at a later date, the report that you prepared may be used to verify that the weld was inspected and was acceptable, or that it was inspected and was not acceptable.

Qualification Records

The welding inspector should have available to him the test records for qualifying welding procedures, welders, and welding operators. The welding inspector reviews these test records to verify that welding procedures, welders, and welding operators are qualified in accordance with the requirements of the code and any additional requirements in the technical specification. In addition, the welding inspector reviews the welder qualification maintenance records on a periodic basis to verify that the welders and welding operators have used the welding process for which they are qualified within the required time period.

Inspection Reports

The welding inspector usually documents the inspections that are performed in an inspection report. This report may be a formal document with space provided for identifying the weldment that is inspected by drawing number, piece number, or weld number; the results of the inspection; the inspector's name or symbol; and the date of the inspection. Alternatively, the welding inspector may document his inspections in a daily report or in a log. Regardless, the same information described above is usually recorded in documenting the inspections that are performed.

Examination Reports

The welding inspector often reviews the nondestructive examination reports, testing reports, and other reports prepared by the individual performing the examination, inspection, or test. In this case, the welding inspector verifies that the item is identified, the procedure that was used is correct, and that the results as recorded in the report are acceptable. If the welding inspector is qualified and review of the radiographs is required by the quality program, the inspector may verify that the radiographs and the accompanying report meet the requirements of the technical specification.

SUMMARY

Your daily routine as a welding inspector has been reviewed in this final module of our course. Your work involves preweld inspections, inprocess inspections, final inspections, and the documentation of that work.

Before any welding begins, you check the proposed welding procedure, the conformance of materials to be used, edge preparations and joint fitup, the welding equipment, any purging operations, and the qualifications of the welders and welding operators.

While welding is in process, you check the welding technique, shielding, interpass cleaning, temperature controls, essential welding variables, and any repair welding.

Your final weld inspection checks postheating, cleaning, and weld identification. You perform visual inspection and supervise nondestructive and destructive examinations. Finally, you document the inspections that have been performed and prepare a report of your work.

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