Arc burns!!!!!

Date 09-28-2008 00:22

On every pipeline job the inspectors are :absolutely obsessed" with arc strikes.
They are a cut out in that world.
It's just the way it is.
You have to be extreemly carefull, and keep all fire inside the bevels. It really is that simple.

JTMcC.

By 1mancrew (**)

Date 09-28-2008 00:32

I appreciate the response but I'm still just a little fuzzy on what an arc burn truly is. Is an arc burn and an arc strike the same thing? I thought an arc burn was the result of actually hittng the pipe with the rod outside the weld area and not just a little long arcing!?!?

Thanks

By texasrigwelder (**)

Date 09-28-2008 00:57

yes and arc burn is the same thats all ive ever called it and it suposeofly its hurts the stuctur of the pipe it hardins it in that spot and that puts stress on it, arc burn is auto cut out un less u hit with a tiger disc around ur bead or hot pass then it will blue up and look the same after its capped

By TRC

Date 09-28-2008 01:01

Hey 1man, even though the 20th edition of 1104 now covers arc burns the botton line is that IMO, it would take so much time to measure and verfiy that the burn is acceptable or not is faster just to cut it out... end of story. Just like a crack, 1104 allows a crack to be repaired but by time all the testing is completed prior to the repar it's faster just to cut it out. Ted

By Jenn

Date 09-28-2008 02:41

Here, some discussion and interesting photos in a thread from not too long ago:
http://www.aws.org/cgi-bin/mwf/topic_show.pl?pid=117081;hl=arc%20strikes

By JohnJohn (**)

Date 09-28-2008 13:14

Here is proof that it is not an automatic cut-out. This is on a meter station for a 8 in line south of DFW. I counted three total arc strikes on this station plus this ugly a** tie in. Maybe it was one of those no-grind jobs?

JohnJohn

Attachment: UglytTie-in.jpg (73k)

Attachment: ArcStrike.jpg (160k)

By 522029

Date 09-28-2008 13:44

That is some awful looking dirt-daubing!!!!

Griff

By vagabond (***)

Date 09-28-2008 14:12 Edited 09-28-2008 23:04

If you ever get a chance to see microscopic pics of what arc-strike does to metal you will be a believer in a hurry. The nearest thing I can compare it to is spider webs emanating from the affected area. That being said, I am a realist and I have welded for over 20 yrs. and realize that stuff happens. As an inspector if I don't find it, it's not a cut out. Back when I was younger and ignorant of such things I have fixed a couple of arc strikes and ground them down nicely with a tiger disc, rubbed a little dirt on it and no one was the wiser. I'm just bringing this up because the topic surfaces here somewhat frequently and it puzzles me as to how inspectors are running across them. Most arc strikes occur in an area where the "fix" isn't so noticeable.

By rockin d (**)

Date 09-28-2008 15:40

I have seen an X-ray of a arc burn & yes it looks like a spider web on the inside , it will eventually revolve in to a pipeline leak----

By ZCat

Date 09-28-2008 15:57

I've seen steam pipe that was 50 years old and just covered with arc strikes that didn't leak. You could see that they deliberately struck outside the bevel and dragged over to it to start their bead.

But, for cost purposes, pipelines typically use the thinnest pipe that will suffice, so there is no room for error. Are you using a speed lens? Might help some, although not in the case you mentioned.

Those pics look like they let the helper weld that day.

I worked with a guy once, he was hot passing on a line. The inspector told him if he saw that file in his bucket one more time, he was gone!

By JohnJohn (**)

Date 09-28-2008 16:12

Funny thing is, I pointed it out to the Hot Tap foreman and he said he see stuff like that all the time... above ground and below. I agree with the affects it does on pipe. I worked Union Iron and they always gave me sh** about how careful I was striking an arc on moment connections... inspector sure appreciated it though. I actually have more trouble coming off a weld than striking in.

JohnJohn

By dbigkahunna (****)

Date 09-28-2008 19:06

Older pipe, pre 1970's was typically a lower grade. On high grade, X52 and above, arc strikes can cause catastrophic failure. Even on low grade pipe, the arc strkes causes the spider cracks typical of the defect. However older pipe is softer and usually thicker. And if the crack works its way to .250 before it reaches its maximum and you have .375 pipe no issue. IF it is 0.188, then you have KABOOM!

And on X65 pipe, cracks can go through .500 of thickness. DOT 192 and 195 allow repairs. However it requires the use of Ammonimum Perosulfate. A corrosiove. Most companies corrosion departments will not allow the application of corrosive material to pipe. So while AB and cracks CAN be repaired, the cost to repair one is equal or more than a Xout, and then you know you have the defect.

Also inspectors know about the tiger pad trick. If I see one, I figure the welder is trying to pull one over on me and I dont like that. Let the inspector make the call about the AB. Welders make weld after weld w/o a burn. Become one! And no pipeline welder has passed every test and never had a AB.
BABRT's

By JohnJohn (**)

Date 09-28-2008 16:07

Coincidently, they were doing a hot tap about 100 yards from this station. The line was leaking because there was a leaking sewer main RIGHT above it. One of the maintenance men at the plant decided to look in the man hole with a lit cigarette... BOOM! Luckily he just lost some hair.

JohnJohn

By vagabond (***)

Date 09-28-2008 19:49

I can usually tell a guy that has pipelined because he will light off differently than one who hasn't. I'v noticed a lot of pipliners will put the rod in the stinger then rest it horizontally on the top tack, flip down the hood and drag the rod downhill to start off. Others will try to hold the rod close to where they want to start, flip the hood down and poke the rod into the bevel and sometimes miss. I suppose a speed lense might help, but I never could get used to them and I have a spendy one I still don't use it much unless it is junkyard welding.

By johnnyh (***)

Date 10-01-2008 03:30

Did the sketch call for that weep hole?

By raftergwelding (*****)

Date 09-28-2008 19:46

i wouldnt even call that dirt dobbin wow thats nasty just plain ugly

By JohnJohn (**)

Date 09-28-2008 21:58

That's what inspired me to try pipelining. I'm no Golden Arm but I take a lot more pride in my work than this guy did.

By jkin

Date 09-29-2008 15:17

Who ever made those welds has no pride at all, Looks like cancer in a baboons a**.

By dbigkahunna (****)

Date 09-28-2008 22:52

The second photo is a classic example of old time welding. Notice how wide the cap is. Legend is the old El Paso Pipeline inspectors had better see those arc strikes coming into the weld so they knew the welding rod was good and hot before they started welding with it. Times have changed. It is known arc strikes are a detriment to the weld and can cause delayed problems.
BABRt's

By JohnJohn (**)

Date 09-28-2008 23:28

Funny thing you say that about EL Paso. At my grandfather's place in NM there is a meter station with some of the prettiest "Texas Weave" you'd ever see on the WOL's. The cap welding was all Lo-Hi and done on the rollout, it is beautiful. I wish I had pictures to show the comparasion. But your right, it's old school.

JohnJohn

By rockin d (**)

Date 09-29-2008 01:52

Guy's it all goes back to taking pride in your weld .I love when some green hand comes & ask's me how i capped a weld , or how i went 14 miles on bead w/ no repairs , im so bowed up sometimes i don't fit through a door , that's craftsmanship , & damn proud of it . BUT I have my days , & nobody's perfect..

By medicinehawk01 (**)

Date 09-29-2008 02:18

Arc burn or arc strikes are said to cause a stress riser which in time could lead to a failure in the HAZ (or weld) according to ASME B.31.1 (or B.31.3) I forget. It really depends on how deep (IF at all) this defect is. Since I know nothing about API 1104 which is the code I assume you are welding to if it's pipeline, than I would question that as well. It could be that particular inspector was (maybe) a former weldor who had issues with arc strikes himself and feels it's his obligation to harp on any he sees. I don't know, but now that you do all you can do is "play -the-Game" and not leave anymore.
I once had a repair on a 16"- chilled water line (underground examined via asme b.31.1 radiography) where there were 4 pores of porosity and you were only allowed 3 pores in any 12" of weld metal. I made the repair and then got rejected because of concavity of the repair. I argued that I had removed the porosity, but to no avail and had to make the repair again (3rd times a charm). It really is a matter where you are subject to the person who is inspecting/interpeting and what can you do? I had to be more careful and once I had my eyes examined...... I found out that I was not seeing like I used to and had to get reading glasses to bring me back up to my "Bust-Free" demeanor and I have not had a repair since.
Again, a valuable lesson I learned as really it was just the guy doing his job and not accepting anything less than what the code permits. It is hard to argue with someone who does the Best they can and when it is their job to make sure you are doing the best you can............. all you can do is give it to them.
Be well,

Hawk

By dbigkahunna (****)

Date 09-29-2008 23:39

You need to see ASME B31.4 Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids section434.8.7(a) which specifically addresses arc burns and you can access CFR 49 Part 195 Section 195.226 which is the federal requirement with requires arc burns be repaired or removed. This follows ASME B31.4 which DOES allow grinding and testing of the spot. And most customer specificaitons require AB be cut out reguardless.
I have seen a AB on 0.375" X80 which goes all the way through the pipe. Granted it was caused by the hot pass hand who was welding at the upper end of the procedure, but DOT requires arc burns be addressed.

BABRT's

By 1mancrew (**)

Date 09-30-2008 00:53

Thanks for all the feed back guys!! I guess the bottom line is not to give these inspectors ANYTHING that sends up a red flag in their eyes! I know; way easier said than done!

The tough part is when this guy called a piece of spatter an arc burn. My fault; I shouldn't have bothered to file it. That was the red flag he saw. He thought I was trying to hide something on him. I honestly wasn't!! I was just trying to dress up my work a little but being a little new in the pipeline world it never really occured to me how this must have looked to an inspector.

Everyone tells me that a pancake hood with an auto lens will help, so I ordered one today from Tom Waters. Should be here near the end of the week. We'll see how that works. I've been using my heavy old pipeliner shell hood. Some of these ol' Texas hands call it a "corn scoop"!

I've learned a lot on this job and I'm learning new things everyday. All in all, a very positive experience. Jobs like this will give you a sense of discipline that will help you out a lot down the road!!

Thanks again all!!

GH Weidman

By ZCat

Date 09-30-2008 01:39

First time I got a spark on my lip using my new pancake I went back to the old corn scoop. haha

By 1mancrew (**)

Date 09-30-2008 01:45

Lovely, I can't win for losing! LOL

By BryonLewis (****)

Date 10-01-2008 21:30

I have wondered for days about the "pancake hoods". I have never seen one before. I finally looked it up online. They look unsafe. What is the deal with them. Good or not?

By Metarinka (****)

Date 09-30-2008 02:14

As we all know all arc burns, porosity, defects etc aren't caught. When ever any project is designed there are safety margins in the material and design.
although the pipe has a 70,000 lbs tensile strenght it might really be 76,254 lbs
although the pipe is rated for 10 psi it might really handle 17
etc etc

so generally arc burns and other such flaws probably fall within the margin of safety that is the last and final catch-all

However, since these flaws aren't accounted for they can lead to long term ramifications or even catastrophic failures. so they should always be avoided. also you can garauntee the code books are written with blood and money. They have some smart minds working on smart code, they don't put in things to make your life tougher and because of old wives tales, they put rules like that in there because pipes have broke people have died and companies have lost millions of dollars.

In terms of what happens in an arc strike:
While it varies from material to material at the basis an arc strike produces a very small extremely concentrated burst of heat with a extremely fast cooling rate. Since the arc strike is very short one very small patch of mterial gets heated up and cooled down. This creates internal stress, can change grain structure, and causes cracking (due to oxidation or contamination). Furthermore unlike a weld puddle the cooling rate is much faster. Anyone who has ever followed low hydrogen procedures or had to do a postweld heat treat knows that cooling rate is an important factor.

*super technical*
now in an allotropic material (suh as iron alloys) there are multiple grain structures depending on temperature and carbon content. Steels are generally Ferritic at room temperatures but austenitic above a critical temperature. If the material raises above the critical temperature (which happens when welding) and not allowed to cool slowly back below it then the grains get stuck as austenitic material. Which more importantly has the tendency and ability to form martensite ( a very hard and brittle structure that will crack). Anyone who has ever welded austenitic stainless steels know that there is much effort placed in keeping the ferrite content within a certain value so as to decrease the likelyhood of martensite formation.

*end technical*

Anyways at the basis arc strikes act as a stress riser and grinding them out won't remove the heat affect zone beneath the surface that could possibly have a changed grain structure and internal stress that would need to be stress relieved. It's much easier to A) no strike an arc in the base material to start with B)repair or cutout damaged base material. The alternative C) weld fails in 5 years when the part is 4 feet under ground is not an attractive one.

By peters077 (**)

Date 09-30-2008 03:01

Things have changed since i started welding 15 years ago the stuff i used to get by with are almost grounds to be fired. If i were to put some stuff that looked like the pics i know i would be. The best thing to do is just be carefull try not to screw up and what ever you do DO NOT get in to who is rightand who is wrong with the insp. even if you show them in black and white were they are wrong yoou will still end up doing it there way. it is better just to say " ya you are right sorry i will try to do better" and after you are no longer the "new guy" they wont mess with you nearly as much, you will still be nitt picked from time to time even if you know him from wen he was workin with you and and heput out way worse stuff and got by with it. As for the pancake hood all i can say is good luck i used mine 1 time and that was enough. i love my automatic and wouldnt anything else....

By jrw159

Date 09-30-2008 13:56

My first experiance with arc strikes:

Building buses using 304 SS thin wall tubing .083 & .110. GMAW 309L. The welders had a bad habit of burning off the excess wire from the end by strikeing it against a tube, leaving an arc strike. Third party inspector saw this and we ended up inspecting all frames up to the front of the line, and cutting out and replaceing any tube found to have an arc strike.

The metulurgical issues aside, it is plain and simple poor workmanship habits.

On a pipeline job once, the instructions were, if the arc strike exceeds 1/32 in any direction, IE depth, width, length, it was a cut out. I personnaly have never seen an arc strike that was less than 1/32 in an direction.

It seems to me the simplest fix is between the shoulder and the holder. Don't be sloppy, and you will not have the issue. I say this as a welder AND an inspector.

jrw159 :-)

By swsweld (****)

Date 09-30-2008 14:58

I agree. Accidents happen but they should be few and far between.
1/32" Not even with GTAW could I make one that small. And I'm very talented with arc strikes :)

ASME B31.1 states 127.4.1 (D) CAUTION: Arc strikes outside the area of the intended weld should be avoided on any base metal.

Caution was in caps. I didn't do that for emphasis. I think an inspector could reject arc strikes based on that para. It does give a little wiggle room using "should"

Curious as to how you guys would handle arc strikes per 31.1 127.4.1

I don't see it specifically addressed in ASME 31.3.
341.3.3 An examined item with one or more defects (imperfections exceeding the acceptance criteria of this code) shall be repaired or replaced.

By scrappywelds (***)

Date 09-30-2008 15:22 Edited 09-30-2008 15:25

I have read this thread with interest. In the boilers where I do alot of my welding, it is hard to get your head, arms, body, and a mirror to weld with to see. This being said there are millions of arc burns in there, it's hard not to. We just dress them down with whatever tool you like, and hope there is no leak. Depends on where the arc burn is at the tubes could be under 2500# of pressure. It would be impractical to cut out arc burns. Try as hard as you like but at some point in time you will arc off on a tube, and get mad that the rod you just spent 2 mins. bending to get into position to weld is trashed.

By 1mancrew (**)

Date 10-01-2008 01:21

I'm only guessing but I would imagine you are using a much heavier walled pipe in the boiler room thus mitigating arc burns as a major factor. On a pipeline, the energy companies use the thinest pipe possible to save money on material costs. It also makes the welding quicker since there is less bevel to fill up an therefore greatly reduces labor costs. That having been said, there is little room for error in the quality. The one I'm on now X-rays every single joint and has a very low defect tolerance. A strict application of the API 1104.

By 522029

Date 10-01-2008 01:43

Boiler tubes are very thin! This enhances heat transfer. Scrappy will have to help my bad memory on this but on the power boilers I used to run (never welded on) two of them had tubes of about 0.125" and the third one's tubes were about 0.090". Give me a little leeway on the dimensions as it has been 6 years since I left that PowerHouse.
For those that have never seen the inside of boiler these tubes are virtually side by side and next to the wall.

Griff

By scrappywelds (***)

Date 10-01-2008 01:45 Edited 10-01-2008 01:50

we do alot of heavy wall tubes .250", but the waterwalls where I work are .140" wall thicknest down to .040" with the scale on the inside. Try putting a padweld on that thin crap, needleast to say it sucks. We do have on one unit a main steam header in the penthouse with a 7" wall thickness. We shoot to B3.3 Boiler and Pressure Vessels code. Yes the tubes are max. 2" edge to edge, but usally there is a 1/2" membrane in between the tubes, can be side by side(no space) have to wedge them apart to weld.

By 522029

Date 10-01-2008 13:46

Thanks for the additional info.

Griff

By 803056

Date 10-01-2008 02:04

I believe it was John Wright wrote about a demonstration he has performed for his welders to show the affects of an arc strike.

He described dragging the electrode over the surface of a plate and then bending the plate so that the arc strikes are within the bend radius and subjected to the tensile loads. The results are typically cracks due to the microstructure resulting from the arc strike. I tried the experiment and it worked as predicted.

As Metarinka stated, the rapid cooling of the metal melted by the momentary arc results in a hardened heat affected zone under the visible arc strike. The higher the strength of the steel alloy, i.e., higher carbon equivalency due to alloy additions, the sensitive the HAZ to the hardening effects of the rapid cooling.

In the early days of pipelining the steels used were essentially low carbon steels. As such, the materials did not develop the very hard heat affected zones under the arc strikes such as we experience with today's high strength, high performance steels. The newer line pipe materials, having higher carbon equivalencies are also more susceptible to delayed hydrogen cracking, thus low hydrogen electrodes that have been properly stored are required.

The Navy requires the arc strike and the adjacent HAZ to be ground out and blended. If the the carbon content is above a certain threshold, the blemish has to be etched with acid to ensure the HAZ is completely removed.

Times and technology are changing. We in the welding industry have to keep up with technology. We need to be aware of how our daily practices may have unexpected consequences. It is better hear about and learn about the possible consequences here in the Forum than on the job site. Welcome to the School of Hard Knocks were we learn from each other's mistakes. Hopefully, we won't repeat them.

My apologies if it wasn't JW that told us about the demonstration I mentioned in the first sentence.

Best regards - Al

By Jenn

Date 10-01-2008 02:30

Al,

That demo is pictured, and post you speak of, in the thread that I cut and pasted in my post above. It was what I pictured in my mind when this subject came up again..... a very vivid image - one I'll probably never forget. I think it will make a believer out of you.

To save some searching for anyone looking for it. LOOK UP. :)

Jenn

By 803056

Date 10-01-2008 03:09

Thanks Jenn;

That is the thread I had in mind.

Best regards - Al

By vagabond (***)

Date 10-01-2008 03:41

1/32" huh OK I'm revising my standards arc strikes are now allowable. Just not very big ones, I love it. That will be right up there with "allowable porosity" I get into it all the time with welders who actually are somewhat versed in the code(s). But a certain amount of porosity is allowable, and yes it is. . . . . but not according to my companies standards. We are instructed to not allow any, period. And I agree with that because you never know how deep it can be.

By pipewelder_1999 (****)

Date 10-01-2008 03:49

Let me give a little background. I have both inspected and welded a few boiler tubes. And though there is a considerable skill involved, the margin of safety built into a tube is probably much greater than that of a pipeline. I do not have any idea what pressure they operate under but a 42" diameter pipe with a 3/8" wall would have the same unit stress as a 2 1/2" od boiler tube with a .015" wall thickness given the same internal pressure. Leave an arc strike on THAT ! I am not sure if the formula is the same for small heavy wall pipes as it is for large thin wall so I may be way off.

If the above is true, an arc strike or any discontinuity for that matter could have a far more serious impact on the large diameter pipe in comparison to the small tube.

Its my opinion that you REALLY have to do something bad to make a waterwall tube fail because of a circumferential butt weld. I have cut out a few waterwall tubes and even SH tubes with 30% of the joint penetrated and the rest unwelded.

I have no pipeline experience at all but would love to get some. If one ever comes through Northeast Mississippi, let me know. I may make a decent helper.

By jrw159

Date 10-01-2008 04:08

"I may make a decent helper."

Smarta**!! LOL :-)

None the less, a good post.

jrw159

By pipewelder_1999 (****)

Date 10-01-2008 11:18

I was kinda serious. The pipeline industry is something I have never worked in. I have put up structural steel (for boilers), welded tubes and pipes in various settings, nuc work, fab shops for structural, fab boiler parts, fab pressure vessels, fab heat exchangers, chemical plants, food plants, gas turbine rebuilds, blah blah blah

Much of that experience is probably much different than pipeline work (im guessing). Without seeing what goes on and how things work, I would be feel awkward saying I would like to "go try pipeline welding to see what its like" without clarifying that I would start at a position that reflects my abilities. I would feel like making light of the special skills needed by welders and fitters in that industry. I am pretty sure with all of my experience, I would be of fairly low value as a helper which I am sure has a special set of skills and knowledge that makes "good ones" and "bad ones".

I am pretty sure I could pick it up. Of course those times welding tubes when I looked like Darth Vader with a 3/32" 7018 light saber swinging around would have to be overcome.

Thanks for the reponse though !

By jrw159

Date 10-01-2008 13:19

Pipewelder,
I am quite sure you would pick it up quickly. :-) I would venture to say you would be a helper for a very SHORT period of time, unless that was where you wanted to stay.

jrw159

By 3.2 Inspector (***)

Date 10-06-2008 13:31

Nice in depth reply.....nice.
I dont agree to your option B, in my experience its easier to grind the area(including removal of HAZ) and perform MT in order to assure no cracking has ocurred during cooling.

A simple measurement can be done to assure the thickness of the pipe still is within spec.

3.2