Want to Be a Certified Welding Inspector

8/10/2019 Want to Be a Certified Welding Inspector

1/19

So you want to be a certified welding inspector?

A good welder doesn't necessarily make the best inspector

ByDan Davis

July 8, 2010

Not many people who enter the welding profession think about their long-term career path. A certified weldinginspector may be the next logical step for the right welder.

Figure 1A certified welding inspector has to know when he doesnt understand something completely and consult a

reference to ensure hes making the right call. Photo courtesy of Knight School of Welding.

Sometimes welders get to the point in their careers when they wonder what the next step is. Some want to leavethe daily gymnastics required to prep, weld, and clean fabrications. Others want more responsibility and more

money. The life of a certified welding inspector may be right for them.

The U.S. Bureau of Labor Statistics (BLS) reports that the mean annual wage of a welder in architectural andstructural metals manufacturing, as of May 2009, was $33,330. That manufacturing segment employs thelargest number46,350of welders, cutters, solderers, and brazers, the name the BLS uses to describe theparticular job area. If you look closely at a manufacturing segment in which inspection is a key component ofproduction, such as aerospace product and parts manufacturing, you see that the mean annual wage jumpsdramatically, to $47,330 for inspectors, when compared to the wage paid to welders. Manufacturers see weldinginspection as a much-needed skill for which they are willing to pay.

The jobs are available as well. A quick look at the American Welding Society job board at the time of this

writing showed 10 out of 24 job openings were for inspectors or quality control personnel. A search onCareerBuilder.com revealed 55 welding inspector jobs. The job locations spanned the U.S.

Good compensation and plenty of opportunities for those interested in becoming a certified welding inspector(CWI) are expected to continue for the foreseeable future. That, however, doesnt mean that every welder issuitable for the job.

Time to Hit the Books
http://www.thefabricator.com/author/dan-davishttp://www.thefabricator.com/author/dan-davishttp://www.thefabricator.com/author/dan-davishttp://www.thefabricator.com/author/dan-davis


2/19

David Tofaute, the executive director of the Knight School of Welding, Louisville, Ky., is candid when talkingto students interested in the schools 80-hour CWI course.

Its something that a lot of schools typically dont do because its so intense, he said.

The course stretches for two weeks, but even when that is done, the instructors might stretch it out a day or two(see Figure 1). [The students] are likedeer in the headlights, Tofaute said.

So what does a CWI have to know? It helps to know a little bit about everything. Depending on which codes(for example, D1.1:2008 applies to structural steel; API 1104 covers welding pipelines) would-be inspectors areinterested in, they need to know exactly what is stated in the code and how to find sections of the code quicklyto verify quality welds or substantiate the need for rework. They need to know about welding processes,terminology, and symbols and how different materials react during the welding process. They need to learnabout nondestructive testing and visual clues that suggest a weld is acceptable or not.

Paul Cameron, a senior welding engineer for McNeilus Truck and Manufacturing Inc., Dodge Center, Minn.,and author of the Arc Welding 101 column inPractical Welding Today, was a welder for 13 years before hedecided to take the next step. He knew that climbing up the career ladder would require a lot of extra work, buthe didnt let it deter him from his goal.

In 1993, as a third-shift welder, I took the AWS CWI seminar. I took what I learned, studied, studied, andstudied, and six months later took and passed the exam, Cameron said.

Figure 2Being a welder is a helpful step on the way to becoming a CWI, but its not required. For example, if a person

has an associates degree or higher in engineering technology, engineering, or a physical science; has three

years of work experience; and has passed a vision test, he or she is qualified to take the CWI exam.

Experience Counts

As Cameron found out, welding experience is helpful. AWS actually stresses some sort of work-relatedbackground before taking the CWI exam (see Figure 2).

Those with at least a high school diploma and at least a years worth of engineering or technical schoolcoursework need at least four years of work experience. Those who didnt graduate high school or have not

obtained a general equivalency degree need at least nine years of work experience if they have finished at leastthe eighth grade and 12 years of work experience if their academic career finished before completion of theeighth grade.


3/19

AWS is serious enough about the work experience requirement that it asks for written verification ofdocumented employment when someone submits an application to take the CWI exam. If acquiring the proof ofemployment experience is not possible, then the applicant has to provide a detailed affidavit that confirms anyprevious work experience.

Cameron added that a varied work experienceor an unstable work history as one human resourcesrepresentative described itmay help as well. With experience in oil rig fabrication, mining equipment repair,construction, and manufacturing, Cameron said he has worked with just about every welding process

imaginable and has learned to weld to multiple codes.

Many welders will work in a single industry with a limited number of processes their whole life, he said. Apipefitter may never pick up a MIG or flux-core gun. An ironworker may never manipulate a TIG torch. Aproduction MIG welder may never pick up a print. Each can be a very successful CWI within their industry, butoutside their industry, they may feel like a fish out of water.

Communication Is Key

So the would-be CWI needs to know about quality weld joints, welding codes, and testing methodologies, butall that knowledge does no one any good if it cant be communicated clearly. The information needs to be

reported to the welding department in a clear and accurate manner that leaves out the vague language and sticksto the basic facts.

Cameron shared the details of how a report should be written after recently receiving a report that described aset of bend coupons for a welder qualification test. The original report read: One coupon looked good. Theother had a couple of places that didnt. Cameron offered this alternative: Coupon 1, root bend, one

discontinuity less than 132. Acceptable. Coupon 2, root bend, one discontinuity greater than 132, but less than

18. One discontinuity greater than18. No corner cracks. Unacceptable.

CWIs also have to step up and deliver news that may not be welcome. Thats why it helps to communicate in

respectful tones. No one likes to be told they made a mistake.

Tofaute said the schools CWI recently certifieda weld for a nearby manufacturer, but the quality controlinspector for the client company questioned the validity of the inspection because the part failed an internalquality test. The client company sent the part back, and the CWI at the Knight School of Welding discoveredthat the part was painted. Apparently the manufacturer tested the part after it was painted. The CWI had to placethe phone call that notified the quality control inspector that he has to test the part before finishing occurs, notafter.

Its like talking to a doctor, Tofaute said. When you call a certified welding inspector, hes not always going

to give you the answer that you want to hear.

Independence Every Day

The ability to communicate clearly can keep a production floor running smoothly, but if the communicationisnt based on an honest assessment of a weld, everything is at risk. Tofaute said that a CWI has to be

independent by nature, and that personality trait needs to be evident before taking the CWI exam. Because hewill be speaking with other welders, a supervisor, and engineers on a regular basis, and lawyers, scientists, andthe company president on a not-so-frequent basis, a CWI needs to be able to speak the truth without feelingpressure to alter the story for the audience.


4/19

This can mean that a CWI does not accept gratuities of any kind from customers. That includes even the randominvitation to lunch or dinner.

I still accept these invitations, but I make it clear that I can attend only if Im paying my own way. Folks find itodd, but it is something that works for me, Cameron said.

Actually, the AWS code of ethics for welding inspectors clearly states that they shouldnt accept any

compensation and should avoid any type of conflict of interest with the employer or client. This keeps not only

the welding inspector clear of potentially dubious practices, but also keeps the public safe. The AWS code ofethics sums it up nicely: Welding inspectors shall act to preserve the health and well-being of the public byperforming duties required of welding inspection in a conscientious and impartial manner to the full extent ofthe inspectors moral and civic responsibility and qualification.

Study, Study, Study

If a welder has the welding knowledge, the commitment to study, the ability to communicate, and a willingnessto be honest and independent, a CWI might be a logical career move. Before embarking on a new career path,however, the welder should keep in mind the need to hit the books to attain this certification.

The AWS requires a minimum score of 72 percent in each of the three sections of the test: Part A, a two-hour,150-question, closed-book test on fundamentals; Part B, a two-hour, hands-on test of 46 questions that requiresthe test-taker to use visual inspection tools and a sample code book; and Part C, a two-hour, open-book test of40-60 questions that calls for finding the right code in the right code book. If the test-taker fails any part of theexam, he has to wait a year and also take 40 hours of additional professional training before retaking the exam.

There is one test for which a would-be CWI doesnt have to study: the vision test. The candidate has to provenear vision acuity, either with or without corrective eyeware, on Jaeger J2 (the eye chart used in mostoptometrists offices) at not less than 12 inches, according to Section 6.1 of AWS B5.1, Specification for the

Qualification of Welding Inspectors.

In short, the CWI candidate has to have good vision to see what lies before him and the work that will berequired to achieve the official certification.


5/19

Upfront welding inspection considerations

ByCarl Smith

July 7, 2010

Welding inspection involves much more than simply checking the accuracy of welds after they are made.

Inspectors must be knowledgeable about codes, standards, materials, and other fabricating processes.

Welding inspection is not something to be taken lightly. Lives can depend on the accuracy of the inspection.Failed welds that cause the loss of life or property make the news and technical journals. These failuressometimes are blamed on the welding inspector. If the inspector had done his job properly, the harmful eventcould have been avoided. In some cases this claim is justifiable; inspectors make mistakes just like any otherperson in the fabrication chain. However, an inspector cannot inspectquality intothe product. The quality of aweldment must be established at the very beginning of the project and followed through to the end. If any stepin the job is not established and carried out with quality as the top priority, the possibility of failure exists.

In years past, poor welds caused many more catastrophic failures than occur today. Boilers exploded, ships

sank, buildings and bridges collapsed, and pipelines blew up frequently. These disasters became far lessfrequent as codes and standards were established.

Which Code or Standard?

The American Society of Mechanical Engineers (ASME) worked diligently to establish rules for fabricatingboilers, pressure vessels, and piping. The American Welding Society (AWS) established rules for structuralfabrication and erection. The American Petroleum Institute (API) continually is quality and safety for pipelinesand related facilities.

One of the first things an inspector must know is which code or standard should be used for the inspectioncriteriaboth the code of construction and the code to qualify the welding procedures and welders. Theserequirements must be outlined in the job specifications. The inspector should not make assumptions or rely onhis judgment to set the standard. If it is not written in the specifications or on the drawings, the inspector shouldnot proceed without clarification.

It must be noted that the ASME Section IX is onlyfor welding procedure and welder qualification. It may notbe used as a code of construction. The AWS D1.1 code may be used for welding procedure and welderqualification and as a code of construction. The API 1104 is for welding and nondestructive testing of pipelinesand related facilities.

Before any welding begins, the inspector must verify that the welding procedures are in compliance with theapplicable code or standard. Sometimes a customer establishes a standard that is not referenced to a particularcode. This is often the case with very large companies, such as Siemens and General Electric. In these cases, thecustomer standard prevails.

Each contractor or company is responsible for establishing welding procedures. No code that I am aware ofallows a company to outsource a test for welding procedures. However, prequalified welding procedures areavailable from the AWS. The user must demonstrate that the company is able to perform to these procedures.Most companies require fabricators to establish and test their own procedures. The API 1104 code does notrecognize prequalified procedures. All codes require destructive tests for the qualification of procedures, andeach code has different procedure testing requirements (Figure 1).
http://www.thefabricator.com/author/carl-smithhttp://www.thefabricator.com/author/carl-smithhttp://www.thefabricator.com/author/carl-smithhttp://image.thefabricator.com/pdfs/upfront-welding-inspection-considerations-figure-1.pdfhttp://image.thefabricator.com/pdfs/upfront-welding-inspection-considerations-figure-1.pdfhttp://image.thefabricator.com/pdfs/upfront-welding-inspection-considerations-figure-1.pdfhttp://image.thefabricator.com/pdfs/upfront-welding-inspection-considerations-figure-1.pdfhttp://www.thefabricator.com/author/carl-smith


6/19

The welding inspector must verify that the welders are qualified and certified to the proper code or standard.Welder qualification is established by testing. A welder who successfully performs a test and receives acertification document is referred to as a certified welder.

Essential and nonessential variables are listed in each of the codes. Some of the essential variables common toall the codes are position, vertical progression, weld deposit thickness, and others related to the specific process.Nonessential variables do not require requalification, but essential variables do. The inspector may require awelder to perform a demonstration for a reasonable cause, such as multiple failures and poor workmanship.

The inspector must observe the joint design to be sure that the procedures cover the type of weld specified onthe drawing. If the procedures and welders are qualified only for welds with backing, then no open-root weldsare permitted. If the procedures and welders are qualified for welds without backing, then welds with or withoutbacking can be used. This variable is common to all the codes (Figure 2).

Figure 2

Material Information

Material traceability is an absolute necessity for all jobs. If a failure occurs and liability is involved, proof ofmaterial quality can hold the key to the cause of the failure. The inspector can only recommendcertainadditional tests to ensure that the material is of sufficient quality for the use.I always advise a client to require

an ultrasonic examination on any material that is 1 in. thick or thicker.

If a plate has lamellar inclusions, they should be detected and reported before any work is done to the material.Material suppliers are required to replace flawed material, but it is extremely difficult to convince a supplier topay for any work that was done before flaws were discovered.

The inspector must check the material test report (MTR) to make sure that it meets the code requirements.Usually the ASTM is referenced for AWS work, and the ASME Section II, Parts A and B, are referenced forASME fabrications. Even when low-carbon materials are being welded, care must be taken to compare thechemical, physical, and mechanical properties to the proper standard. The API piping standard is API 5L.

The inspector may questionthe material selection, but may not rejectthe material if it meets the jobspecifications. The specification for material type is to be determined by the customer (usually the engineeringdepartment or an outsourced engineering firm).

Tracking the Job

The inspector should request a shop traveler -- a step-by-step guide that begins when the job is designed byengineering and proceeds all the way through packaging and shipping. Used for tracking inspections in process,the guide enables the inspector to establish hold pointswhen necessary. An inspector should sign off on eachstep of the fabrication. If a part is cut, bent, or rolled incorrectly, the condition must be recorded and heldas


7/19

nonconforming until a decision is made by the customer. The decision may be to rework, use as is, or scrap.This decision is not to be made by the inspector, but the inspector mustrecord the matter and secure it in thepermanent job records.

Inspection Tools

Inspectors use tools, such as these recommended and assembled in a kit by AWS (Figure 3). These tools, along

with the inspectors knowledge of codes, standards, materials, and processes, help determine the quality,durability, and safety of welded products and structures.
http://image.thefabricator.com/a/upfront-welding-inspection-considerations-inspection-tools-figure-3.jpghttp://image.thefabricator.com/a/upfront-welding-inspection-considerations-inspection-tools-figure-3.jpghttp://image.thefabricator.com/a/upfront-welding-inspection-considerations-inspection-tools-figure-3.jpghttp://image.thefabricator.com/a/upfront-welding-inspection-considerations-inspection-tools-figure-3.jpg


8/19

Building a stronger welding program

Annual Welding Rodeo combines community outreach, fun, and vocational education in two-day sculpturecontest

ByDon Knight

June 7, 2010

Bellingham Technical College launched its Welding Rodeo in 2002 to spur enrollment and raise its publicprofile. Now one of the premier welding competitions in the Pacific Northwest, the event has helped the schooltriple its enrollment in welding and expand its program/skill offerings.

Old cylinder tops, valves, and scrap metal donated from local industry contribute to the Welding Rodeos

success.

Bellingham Technical College(BTC) held its 9th annualWelding RodeoMay 21 - 22, 2010, on its campus inBellingham, Wash. First modeled after theSkillsUSAcontest, the Welding Rodeo has evolved into a sculpturecompetition in which teams compete by creating artwork from scrap heaps of twisted steel and metal.

Thousands of people attend each year, and the finished works go up for auction at the end of the event. Theauction generates scholarship funds for BTCs welding program. What started out as a skills competition hastransformed into a major part of the schools and the communitys identity.

Bellingham isnt easy to find, but now were on the map, said Jer Donnelly, BTC welding instructor.Everyone knows the Welding Rodeo. You go down to Seattle and mention it and people say, Oh yeah, we

know about that. It has a life of its own now. Its amazing. And weve brought a lot of attention to this campus.A lot of people have come to this campus that didnt even know we were here.

Raising Its Profile With Local Industry

Bellingham is the last major American city on Interstate 5 before you reach the Canadian border. Located 90miles north of Seattle, this community is known more for its picturesque vistas of Mount Baker and BellinghamBay than as a hotbed for metalworking.
http://www.thefabricator.com/author/don-knight-http://www.thefabricator.com/author/don-knight-http://www.btc.ctc.edu/http://www.btc.ctc.edu/http://www.weldingrodeo.com/http://www.weldingrodeo.com/http://www.weldingrodeo.com/http://www.skillsusa.org/http://www.skillsusa.org/http://www.skillsusa.org/http://www.skillsusa.org/http://www.weldingrodeo.com/http://www.btc.ctc.edu/http://www.thefabricator.com/author/don-knight-


9/19

Figure 1

To make the eagles wings, the team created a cardboard template and traced the wing pattern with a Magic

Marker. Using a plasma cutter, the artist can precisely and quickly cut out several wings.

Thats one of the big things that drove the Welding Rodeo, said Donnelly, bringing awareness to the public

about the industry. As soon as you say welding to some people, their faces go blank. All they think of are

people that swing hammers and make sparks. Bringing people on campus and showing them this beautiful, first-

class facility is important.

It was also recruiting-oriented, said Don Anderson, BTC welding technology instructor. In our first year, alot of programs were on edge. When enrollment starts going down and you look at the programs weldingwasnt growing at the time. It was scary.

Bellinghams curriculum offers three certificates: a certificate in basic welding skills, a certificate in industrial

welding, and an Associate Degree in applied sciencewelding technology-aluminum/steel fabrication andaluminum welding, pipe welding, structural fabrication. Its training facility features 54 permanent weldingbooths outfitted with multiprocess and stick welding equipment and an additional 50 temporary booths to fitcurrent demand. Enrollment has tripled since the department moved into a new facility in 2005, and the

program has gained two full-time instructors for a total of four and two part-time instructors.

We certify them to Washington Association of Building Officials (WABO) standards, which is based on AWSD1.1, said Anderson. We morphed from there because our local industry told us they wanted more fabricationskills, more well-rounded individuals, but they also want specialization. The industries locally are primarilyboat building, fabrication shops, and refineries. Refineries need pipe welders, and so we decided that we neededa full-bore pipe welding program. And the shipbuilding and repair industry here largely has gone to aluminum,so we needed an aluminum welding program. And then we have the structural steel needs. So that pretty muchdictated to us that we needed to expand our program and give people hands-on training in everything.

Both Donnelly and Anderson, who founded the event together, believe that the Welding Rodeo at least partiallycreated the visibility and excitement that has vaulted the welding program to the third-ranked program at theschool (behind IT and nursing).

I really wonder, if we didnt have the Welding Rodeo here, if wed have this new building, said Donnelly. I

dont think we would have.

Community Involvement at Heart of Event


10/19

Figure 2

Smart teams in the Welding Rodeo start with a plan that includes drawings, dimensions, and even a small-scalemodel.

The Welding Rodeo has exposed locals to the colleges state-of-the-art facility and opened doors to studentswho may not have pursued welding as a career before, including a substantial enrollment and participation bynew female welders. Some participants have even moved on to become members of the BTC staff: The winningartist from the first years event, Mary Kuebelbeck, is now a welding instructor.

We made a 14-foot giraffe, said Kuebelbeck. There were five teams at the time, and the city of Bellinghampurchased the giraffe. It currently sits on the library lawn and is part of the City of Bellinghams art collection.

The event has grown considerably since that first year when Kuebelbeck won. The 2010 event featured twodays of action: one day of high school/college competition and one day of professional competition. As thecommunity involvement has grown, so has participation from the industry. Local welding distributors andequipment manufacturers donate equipment and supplies and run booths at the event. Miller Electric Mfg. Co.has supplied welding, plasma cutting, and personal protection equipment for use during the competition.

Figure 3Working on a table, the artist puts the finishing touches on the aluminum eagle. Notice how the repeated wing

patterns create an illusion of feathers.

That first year we went around and begged and borrowed from different shops, said Donnelly. This yearpeople are throwing money at us for scholarships and letting us know that they want to be a part of the event.Shops are donating metalthey have set the stuff aside all year long. They send teams to compete. Its a greatcommunity event.

Overall, the Welding Rodeo has provided the right mix of fun and education, and it has accomplished the goalsthat Donnelly and Anderson set out with from day one: raise visibility and educate the public on the skill, pride,and art of one of the most important and misunderstood trades in the industry.


11/19

When visitors come to a community technical college, we want to expose them to a real-life career, saidCentral Welding Supplys Marshall Judy, who heavily supports the Welding Rodeo with equipment and timeand is also a BTC welding program advisory board member. These are good-paying jobs that people cansupport families with and have life-long careers. The Welding Rodeo has shown the community this by[connecting with event attendees].

Interested in organizing your own Welding Rodeo? The welding instructors at BTC will gladly share the

template for their success so that other educational institutions can raise the visibility of welding in their

communities. Contact BTC by following the link to theWelding Rodeo.Also use this link to view slide shows ofwinning artists.

Welding Rodeo Tips From Former Champion Mary Kuebelbeck

Mary Kuebelbeck won the inaugural Welding Rodeo in 2002 and has cemented herself as a fixture onBellingham Technical Colleges campus. Kuebelbeck is an exhibiting artist with abackground in structuralsteel, sheet metal, and fabrication who now teaches full-time. While she stopped competing in 2007, she is stillan avid promoter of the event and has offered up a few tips to would-be sculptors participating in similarcontests.

1.

Be Prepared: If youre smart, your team will have a plan. It may have even made some patterns for

cutting (Figure 1). Youll certainly have some type of blueprint with some dimensioning on it. Thereally smart teams will actually make a maquette, or model (Figure 2), prior to the event.

2. Do NotWork on the Ground:You want to work on a table (Figure 3). Get yourself off the groundbecause youll be very sore by the end of the day. Have a canopy, both for rain and for sun.

3. Beware Postlunch Productivity Decline:Get most of your stuff done before lunch because, onceyoure done with lunch, youre really tired, you start to feel all of your aching bones, and you just dont

work as fast. Your brain isnt making all those quick decisions, and you start to doubt yourself a littlebit. The audience gets bigger and bigger, so people distract you.

4. Pick a Leader:There are a lot of split-second decisions to be made. You just have to make thosedecisions and keep rolling and keep moving forward. You cant stop and have a four-person discussionabout one thing. Its best to have one leader, or one leader at the beginning of the day and one leader at

the end of the day.5. Have Fun:There are definitely parts of the day when we get a little testy with one another, but when the

event is over and youve seen what youve accomplished, the feeling is just so great.
http://www.centralwelding.com/http://www.centralwelding.com/http://www.weldingrodeo.com/http://www.weldingrodeo.com/http://www.weldingrodeo.com/http://www.weldingrodeo.com/http://www.centralwelding.com/


12/19

How to relieve stress in welding

Back to basics on stress relief and reducing distortion

November 2, 2009

Relieving residual stress through welding technique as well as temperature control can greatly reduce weld

distortion.

It's a shame arc welding works so well. It's proven, cost-effective. For many applications, nothing comes close,at least not yet. Why is it a shame? Because at the microlevel arc welding induces some serious stress, thanks todramatic temperature changes measured in thousands of degrees.

The welding gun deposits filler metal that becomes molten and expands from its previously cool state as wire orrod. Immediately after being deposited and subsequent fusion between the base and weld metal, the metal coolsquickly. The high-yield-strength weld filler metal contracts, or shrinks, pulling the lower-yield base metal withit. Clamped tight, the metal may stay in place until after welding, but this doesn't make the contracting force goaway. The cooled weld metal still wants to shrink. When the metal is unclamped, the weld metal pulls at thebase metal, and the weld distorts. The degree to which this occurs depends on the weld joint geometry, partdesign, and material grade and thickness. Generally, the higher the metal's carbon content, and the morerestrained a joint is, the greater the stress.

Of course, the metallurgical picture is much more complicated, but that's the basic idea.

Industry has numerous ways to reduce such weld stress. Any method must accomplish at least one of twothings: control temperature and refine the welding procedure, both of which counteract those unavoidable forcesthat come from fusing two metals together with an electric arc.

For this month's "How To" feature, The FABRICATOR spoke with three experts. For heating and weldingtechnique, we spoke with Carl Smith, longtime quality manager and welding technician at KanawhaManufacturing Co. We also spoke with two experts about some nontraditional stress relief technologies: TomHebel, vice president of Bonal Technologies, and Bill Kashin, territory manager for Bolttech Mannings.

1. Refine the Welding Procedure

Setup; electrode selection; along with weld type (fillet, groove, butt, etc.), size, and orientation all affect how aweld joint reacts to stress.


13/19

Prebending or presetting. The base metal can be set up in such a way to compensate for weld shrinkage. Forexample, when two workpieces are preset with one end of the joint together and the far end of the joint slightlyapart, the cooling weld metal pulls the two workpieces until, by the end of the weld, the joint is in the properorientation.

Balance the weld. Double-sided welds, such as double V-groove joints, balance induced stresses and oftenresult in an assembly that's more stable. "This is especially true on thicker material," said Smith. "Two half-inchwelds on either side of a 1-inch plate balances the weld and minimizes distortion."

Backstepping. Backstepping is a bit like moonwalking with a welding gun. You start several inches from thebeginning of the joint and weld back to the edge; then go farther up the joint and weld back to where youinitially struck your previous arc; then go farther up the joint and again weld back to the previous weldedsegment; and so on until the joint is complete. This counteracts shrinkage by focusing the initial stresses awayfrom the workpiece edges.

Intermittent welding. When intermittent or stitch welding meets the design requirements, it not only helpsreduce distortion, but also uses less weld metal.

Consumables. In wire welding, "you can make a 0.035-inch wire lay down just as much as a 0.045-inch wire,"

Smith said. "You can just crank the wire feed speed." He added that lower heat input required to melt thesmaller wire outweighs any heat reduction benefit that might occur with a faster travel speed using a largerwire.

Weld metal: More isn't better. Codes spell out specific weld size requirements, including the maximumallowable height of the bead above the plate. The trick is to lay just enough weld metal to create the strongestjointand no more. A highly convex bead doesn't make a weld stronger, but it does increase shrinkage forces,because more high-tensile weld metal is pulling on the base metal as the weld cools.

Here, technique factors in. "A multipass weld with stringer beads will create less distortion than a weave bead,"Smith said.

The stringer bead technique generally allows faster travel speeds, which lowers heat input. Each pass of the gunlays down less weld metal, which in turn helps control the weld size better.

Welders usually weave only as a last resort, Smith said. "The cover pass on a weave bead can look better than astringer bead, but if a welder knows what he's doing and places his stringer bead properly, he can make it lookjust as good as a weave bead."

Exceptions abound, of course. Pipeline welders often weave downhill, but the beveled opening in a pipeline isusually much smaller than on conventional plate. And "round pieces do not distort nearly as badly as flat piecesanyway," Smith said.

Still, when it comes to controlling distortion, stringer beads usually are best. "Each bead has its own level ofstress," Smith explained. "The wider the bead, the more stress you're going to put into the weld, so you're goingto have more 'pull,' more distortion than a smaller bead."

Fit-up: Small root is best. Solidifying weld metal pulls the base metal, and that effect is exacerbated with anexcessively wide root opening, especially in large weldments and in areas of poor fit-up. "Some situations don'twork with a tight root," Smith said, "but usually, with today's welding machines, you can get by with a 1/16-inch root opening" in many applications.


14/19

Weld from most restrained to least restrained area. This follows similar principles to that of prebending andpresetting, Smith said. Consider a frame with a crosspiece going down the center. The crosspiece, surroundedby the frame, is the most restrained of all pieces in the assembly. So this crosspiece should be welded first. Thecenterpiece, if welded first, is less restricted by the surrounding metal and has freedom to move and expelresidual stress before you go on to weld the frame.

2. Control Temperature

Preheating, maintaining temperature between weld passes (interpass temperature), and postweld heat treating(PWHT) work toward one goal: to control changes in heat levels. The more control you have over heat, themore you can counteract stress, and the less chance there is for weld distortion, especially in highly restrainedjoints. When you slow the cooling rate, you reduce shrinkage stresses and provide more time for hydrogen todissipate, reducing the chance for under-bead cracking.

Material factors. Predicting necessary minimum preheats, interpass temperature, and PWHT depends on theapplication and how restrained the joint in question is. Specific material properties affect how drastically metalwill distort. These include the coefficient of thermal expansion (how much the metal expands when heated),thermal conductivity (how fast it dissipates heat), yield strength, and modulus of elasticity (material stiffness).

As a starting point, refer to the AWS D 1.1 structural welding code, Welding Handbook, guidelines publishedby the steelmaker, and other sources for recommended minimum preheat and interpass temperatures for specificalloys. Generally, higher carbon content equates to higher minimum preheat and interpass temperatures.

Most preheating, interpass heating, and PWHT do not require maintaining a precise temperature, as long as youmaintain a minimum temperature. There are exceptions, though, including quenched and tempered steels. Thesecome to the welding station already heat-treated by the steelmaker, so preheating at a too-high temperature candestroy the material properties; in other words, quenched and tempered steel will no longer be tempered. "Forinstance," Smith said, "the ASTM A514 and A517 alloys should never be preheated to more than 150 degrees Fabove the recommended [minimum] preheat."

Stainless steels can be particularly touchy. "We keep interpass temperatures below 350 degrees F," Smithexplained. "We use distilled water in a spray can. Water on carbon steel causes it to crack. But it has no effecton stainless steel, as long as you use distilled water, which doesn't have any chlorine in it." Stainless's nickeland chromium content make the metal particularly sensitive to distortion, because the elements don't dissipateheat quickly.

As a rule, metals that dissipate heat quickly require higher preheats. Heat-treatable aluminum alloys can bepreheated to 300 to 400 degrees F as an extra precaution against cracking and, most important, to dissipatehydrogen. Aluminum oxide on the base and weld metals attracts moisture, which introduces hydrogen (the H inH2O). Because aluminum dissipates heat rapidly, hydrogen becomes trapped as the weld metal quickly cools.The slow cooling created thanks to the preheat gives time for that hydrogen to bake out of the weld. "This iswhy a welder may often say he's 'boiling the water' out of the material," Smith said.

High-alloy materials such as chrome-moly also dissipate heat quickly and generally require high preheattemperatures. Preheating even the tack welds often is best practice, Smith said. Cracks can start in the tack and"come right through the weld and all the way to the top." He added that certain chrome-moly applicationsrequire preheats of about 400 degrees F and a postweld holding temperature of about 600 degrees F prior tostress relieving.

Copper, which dissipates heat extremely quickly, requires a very high preheat "just to allow the welding fillermetal to flow into the joint and form a good bond," Smith said. Copper more than 1 in. thick may require


15/19

preheats up to 1,200 degrees F. (See Streamline Stress Relief section for ways to apply such high preheatsdirectly to the workpiece, without an oven.)

Coffee break effects: Keep it hot. Imagine you preheat a joint with a torch, weld a few feet, stop, take a shortbreak, and then resume without picking up the preheat torch and heating the joint area again. To minimizedistortion, you should pick up the preheat torch again to bring that material back up to the required interpasstemperature. "You need to maintain the interpass temperature throughout the weld," Smith explained, addingthat heat cycling is especially dangerous with chrome-moly and quenched and tempered materials.

Torch preheating. When preheating with a torch, "we recommend 6 inches on either side of the weld" for largeworkpieces, Smith said, adding that the width of the applied preheat and specific method used depends on theworkpiece material and geometry.

Torch styles vary, but Smith's welders use a multiflame torch with a swirl tip and propylene gas. "Thepropylene gas is not as highly concentrated as acetylene," he said, "and we don't want to concentrate the heatwhile we're preheating."

PWHT doesn't replace preheat. Postweld heat treatment and preheat complement each other, explained Smith,but they don't replace one another. It's true that in some cases localized preheat can serve as a PWHT substitute

when moving the workpiece to an oven for PWHT isn't practical (think offshore oil rigs). PWHT doesn'tfunction as a preheat substitute because it does nothing to reduce the stresses that occur just after you strike anarc on cold, unpreheated base metal. By the time PWHT is applied, it's too late to correct the problem.

3. Streamline Stress Relief

"Over the years welders have perfected techniques to relieve stress and minimize distortion: preheating in anoven or with a torch, using heat blankets, and when necessary sending parts to an oven for postweld heattreatment. Note one common thread among all these methods: time. But certain technologies take alternativeapproaches that streamline the operation and even improve weld quality.

Various alternatives are available, including induction-heating methods. Here, we discuss two options:resistance heating and vibration.

Resistance heat control. A resistance heating pad incorporates resistance heating elements that can raise theworkpiece temperature to the appropriate level before, during, and after welding, to comply with standardpreheat, interpass, and PWHT practices (seeFigure 1andFigure 2). The pad incorporates interlocking beadswoven together using a high-resistance wire. The unit can heat up to 1,850 degrees F. (Smith's company hasused this technology to preheat thick copper plate to more than 1,000 degrees F.)

A temperature controller uses a system of thermocouples spot welded to the part to read the actual metaltemperature, which is monitored throughout the operation. Welders don't have to use temperature crayons tomeasure the preheat temperature. The pad also doesn't have to be removed during welding.

As Bill Kashin of Bolttech Mannings explained, "Say you're welding two pieces of pipe together, and the codesays you need to preheat it to 400 degrees F. You would attach the thermocouple, attach the heating pad, putinsulation on to protect yourself, and raise the temperature up to 400 degrees F. When the heater gets to thattemperature, it will cycle on and off to hold that temperature until you're finished welding."

Readings from the machine also can be saved as a record of the part's temperature before, during, and afterwelding, helpful for code-level or insurance-related work, such as repair jobs at power plants.
http://image.thefabricator.com/a/articles/images/2339/specialized-resistance-heater-welding.jpghttp://image.thefabricator.com/a/articles/images/2339/specialized-resistance-heater-welding.jpghttp://image.thefabricator.com/a/articles/images/2339/specialized-resistance-heater-welding.jpghttp://image.thefabricator.com/a/articles/images/2339/interwoven-beads-resistance-heating-pad.jpghttp://image.thefabricator.com/a/articles/images/2339/interwoven-beads-resistance-heating-pad.jpghttp://image.thefabricator.com/a/articles/images/2339/interwoven-beads-resistance-heating-pad.jpghttp://image.thefabricator.com/a/articles/images/2339/interwoven-beads-resistance-heating-pad.jpghttp://image.thefabricator.com/a/articles/images/2339/specialized-resistance-heater-welding.jpg


16/19

The pads are designed to wrap around the workpiece, with a piece of removable insulation over the joint. Forpreheat, the entire workpiece is covered. You then remove the insulation from the weld joint area and startwelding. When you take a break, you put the insulation back over the joint to help maintain the preheattemperature. The heater pads can then be added to the weld area for stress relief, eliminating the need to transferthe part to a furnace for PWHT.

Vibratory stress relief. Another technique uses something that doesn't seem to be related, but it is: vibration (seeFigure 3).

"Heat is vibration, according to physics," said Tom Hebel of Bonal Technologies. The more something isheated, the faster its molecules vibrate. "We induce a vibration into the part, and the part responds as if it hasthe same internal action when the part is heated up for heat treatment. It's a cool process, but internally, there'smovement."

If you vibrate metal at a certain frequency during welding, it complements the weld heat that vibrates themolten metal at the molecular level. It's roughly analogous to shaking a can of dissimilar-shaped beads or avibratory bowl feeder in a stamping operation, which gets everything to settle and "pack down." The vibrationlevel, Hebel said, is very specific: in the lower, or sub-harmonic, portion of the harmonic curve, just before theamplitude quickly rises and reaches the part's natural resonance.

The device induces vibration into the workpiece and monitors the workpiece's reaction. The more vibrationthat's put into the part, the more it will absorbup to a point. "At a certain point any additional energy willcause the workpiece to throw off the energy," he said.

The trick, Hebel explained, is to induce a vibration frequency that's at a specific point below its resonance point.It's here that the vibration has the greatest dampening effect, at which point it neutralizes the stress induced bythe weld's heat.

Most commonly, the vibratory device is applied after welding to relieve stress, essentially replacing PWHT. Butit also can be applied during welding to improve weld quality through grain refinement and stress reduction. In

fact, applying the right vibration during welding can eliminate the need for PWHT completely, unlesstempering of the heat-affected zone is required.

"When you weld you induce thermal stress," Hebel said. "So when you weld-condition [using sub-harmonicvibration during welding], you're eliminating the effect of thermal stress as it's induced. So after welding, if theeffects of thermal stress aren't there, why send the part to a furnace for stress relieving""

In certain applications, Hebel said, it can replace low-temperature preheating requirements, between 250 and300 degrees F. "Because of the accelerated motion in the base material, the weldment 'thinks' it's preheated."Usually, though, the vibratory weld conditioning complements existing preheat procedures to increase weldquality.

Hebel compares a large steel part with welding-induced stress to an out-of-tune instrument. After welding,temperature drops sharply. At this point within and around the heat-affected zone, the part's natural harmoniccurve shifts slightly, "out of tune" with the rest of the assembly. Counteracting that effect with inducedvibration during and after welding relieves stress as evidenced by the harmonic curve moving back "in tune"with the rest of the assembly.
http://image.thefabricator.com/a/articles/images/2339/vibration-inducing-device.jpghttp://image.thefabricator.com/a/articles/images/2339/vibration-inducing-device.jpghttp://image.thefabricator.com/a/articles/images/2339/vibration-inducing-device.jpg


17/19

Welding Update for Infrastructure: No nonsense

with NDT

Nondestructive testing methods in infrastructure

May 18, 2009

Infrastructure is defined as the basic physical systems that serve a community's population, such as roads,bridges, utilities, water, and sewage. These systems are essential for enabling productivity in the economy, so itis crucial to ensure they are fit for use. Nondestructive testing (NDT) techniques determine whether acomponent has reached its useful service life and needs repair or replacement.

In-service load conditions produce incremental movement in materials and structural members. Whenever aforce is applied to a member, it becomes stressed. The stresses cause strains, or movements, which areexplained by the material properties. In-service conditions cause stress, strain, distortion, fatigue, and corrosion,which can manifest as discontinuities or defects.

A discontinuity is an interruption of the typical structure of a material, such as a lack of homogeneity in itsmechanical, metallurgical, or physical characteristics. A discontinuity is not necessarily a defect. A defect isdiscontinuity that either by nature or by accumulated effect renders a part unable to meet minimum applicableacceptance standards or specifications. In other words, the part is rejected.

NDT Methods

NDT locates discontinuities or defects in critical areas without causing structural damage.

Two fundamental categories of discontinuities that are located by NDT are surface and subsurface

discontinuities.

Surface discontinuities, including cracks, porosity, slag inclusions, excess reinforcement, inconsistent weld beadprofile, undercut, and blisters, usually can be identified by visual testing. To enhance surface VT, magneticparticle testing or liquid penetrant testing is employed.

Visual Testing (VT).VT is the most basic, cost-effective NDT method. It should take place prior to, during,and after welding. Many standards require it before other methods because there is no point in submitting anobviously bad weld to sophisticated inspection techniques. Welding codes always state that welds subject to


18/19

nondestructive examination shall have been found acceptable by visual examination. VT requires good eyesightin the technician and sufficient light, a weld size gauge, a magnifying glass, and a 6-in. metal ruler.

Magnetic Particle Testing (MT). Magnetic particle testing detects surface and near-surface defects inferromagnetic materials only. Defects in magnetized materials will distort the magnetic field, causing a leakagefield. When fine ferromagnetic particles are applied to the surface, they concentrate at the defect by gettingcaught in the leakage field.

Liquid Penetrant Testing (PT).PT detects surface-breaking defects in any nonporous material. A liquidpenetrant is applied to the surface and is drawn into defects by capillary action. Once a preset dwell time haspassed and excess penetrant removed, a developer is applied to draw out the penetrant from the defect. Visualinspection is then performed.

PT also reveals surface cracks and pinholes that are not visible to the naked eye. It is used to locate leaks inwelds and can be applied with austenitic steels and nonferrous materials on which magnetic particle inspectionwould be useless.

The NDT technician may use VT, MT, or PT during the welding operation to assist the welder in revealingdiscontinuities (for example, performing MT on the weld after backgouging to ensure sound weld metal has

been obtained before welding the second side).

Subsurface discontinuities include underbead cracks, wormhole porosity, lack of fusion, slag inclusions, voids,and laminations. Radiographic testing (RT) or ultrasonic testing (UT) help to locate these volumetricdiscontinuities which are not visible on the surface.

Ultrasonic Testing (UT).UT detects discontinuities within the internal structure of welds. The advantage ofthis testing method is its ability to help establish internal integrity without destroying the welded component.

UT is used on ferrous and nonferrous materials and is suited for testing thick sections accessible from one sideonly. It can also locate fine linear or planar defects. UT uses mechanical vibrations similar to sound waves but

at a higher frequency. A beam of ultrasonic energy is directed into the object. The beam travels through theobject with insignificant energy loss, until it is intercepted and reflected back to the UT instrument screen by adiscontinuity.

UT generally uses the contact pulse reflection technique, in which a transducer converts electrical energy intomechanical energy. The transducer is excited by a high-frequency voltage that causes a piezoelectric crystal tovibrate mechanically. The crystal probe becomes the source of ultrasonic mechanical vibration. Thesevibrations are transmitted into the item through a couplant fluid. When the ultrasonic wave pulse strikes adiscontinuity in the test item, it is reflected back to its point of origin. Thus, the energy returns to the transducer,which also serves as a receiver for the reflected energy.

The detection, location, and evaluation of discontinuities become possible because the velocity of soundthrough a material is considered constant, making distance measurement possible, and the relative amplitude ofa reflected pulse is proportional to the size of the reflector.

One of the most useful characteristics of UT is its ability to determine the exact position of a discontinuity in aweld. NDT technicians performing the tests are required to be qualified as a level II in accordance with ASNTstandards. This method requires a high level of operator competence and depends on establishing and applyingtest procedures.


19/19

Radiographic Testing (RT).RT uses X-rays produced by an X-ray tube or gamma rays produced by aradioactive isotope to test welds that can be accessed from both sides. Though it is slow and expensive, itdetects porosity, inclusions, cracks, and voids inside the metal or welds.

In this method, penetrating radiation is passed through a solid object onto photographic film, creating an imageof the item's internal structure. The amount of energy absorbed by the object depends on its thickness anddensity. Energy not absorbed by the object causes exposure of the radiographic film. These areas will be darkwhen the film is developed. Therefore, areas of the object where the thickness has been changed by

discontinuities, such as porosity or cracks, will appear as dark outlines on the film. Low-density inclusions, suchas slag, will appear as dark areas on the film, while high-density inclusions, such as tungsten, will appear aslight areas.

All discontinuities are detected by viewing the weld shape and variations in the density of the processed film.This permanent film record of weld quality is easy to interpret by personnel who are properly trained. Onlyqualified personnel should conduct radiography and radiographic interpretation because X-ray and gammaradiation can be hazardous.

Putting NDT to Work

During bridge fabrication, the American Welding Society (AWS) has outlined the percentage of welds that mustbe tested (D1.5, "Bridge Welding Cod2008, Section 6.7"). For existing bridges, in-service engineeringexaminations follow NDT guidelines provided for new construction in the bridge code.

The code states that NDT (RT or UT) in addition to VT is to be performed to comply with the code by thefollowing frequency requirements:

One hundred percent of each joint subject to calculated tension or reversal of stress, except on welds in verticalbutt joints in beams or girder webs as follows:

1/6 of the web depth beginning at the point or point of maximum tension.

25 percent of the remainder of the web depth needs to be tested.

If unacceptable discontinuities are found in spot RT or UT, the entire length shall be tested. The requirementsfor RT and UT shall apply equally to shop and field welds. MT of fillet welds and partial-penetration groovewelds joining primary components of main members shall be tested.

When inspecting infrastructure, the certified welding inspector needs to know the original requirements of thecomponent being examined. For instance, the inspector has to make certain that the size, length, and location ofall in-service welds conform to the requirements of the code and original detail drawings, and that unspecifiedwelds have not been added without approval of the engineer.

The expected quality of every in-service component is that every significant feature continues to meet the

original designer's intent. NDT examinations provide reliable confirmation of fitness-for-service quality in

accordance with the intent of the original designer.

Want to Be a Certified Welding Inspector

Documents

Transcript of Want to Be a Certified Welding Inspector