How To Repair An Arc Strike Ammonium Persulfate

Commencement you have to grind the area until yous call up you accept gotten the strike out, then polish it with a 120 Grit (or finer) sandpaper.  Look at it with light from dissimilar angles.  Sometimes the hard spot tin can actually be seen visually.  Most times, you accept to grind most 1/32 inch or more to get rid of the phase change surface area under the site of the arc strike.  Arc Strikes on cold fabric are worse than arc strikes on hot textile. Y'all have to be carefull, because oft the minimum thickness is such that very little grind out can be tolerated.

Amonium Persulfate solution should be mixed at a rate of 20% granular Persulfate to lxxx% pure water by WEIGHT.  Unless you take a proficient sensitive electronic food scale, you should employ a postage scale or a re-loaders pulverization calibration.  One gram of persulfate is less than a teaspoon. 4 grams of water is not much either. You need a very small h2o tight container with a plastic lined inside top.  Go along the solution out of the sunlight. This solution can exist carried effectually in your car without danger of fire or explosion.  If the cap vibrates loose, it will rust your car wherever it splashes! You can dip your finger in information technology and you will not become burned.

I recommend you employ it with a Q-Tip.   The solution works fastest on a carbon steel surface that is between 120 and 150 degrees F.  This solution does not piece of work with austenitic Stainless Steels.  (Arc Strikes are less imnportant on those materials anyway.)  You need fresh water to neutralize the action later you develop the indication.  Bottled water is fine.  If yous wipe the surface area with a rag, you lot may smear grease or oil and that will obscure your indication.

It is good "Show-and-Tell" to exercise the polishing and developing of the indication in front of the welder.  So many of them recollect that arc strikes don't mean anything.

Past js55 Date 03-22-2007 xvi:22

WOW.
The info on persulphate is interesting,and certainy of value. But don't ya'll think that worrying about phase changes, 120 grit, lite from dissimilar angles in carbon steel is a flake overreacting in near instances? Unless at that place is some specific requirement otherwise?
Wouldn't an MT or PT checking for cracks be more reasonable?

Past chall Appointment 03-22-2007 sixteen:34

The only time we e'er run into this level of attention is when dealing with gas transmission lines.  Given that nearly transmission line owner/operators wait these lines to be there "forever", it still seems heavy handed, but not that heavy handed.

The real message that needs to become out to the welders is to eliminate arc strikes exterior the weld.  That is e'er the best bulletin, but when they run into only how seriously some owners are, their attention to particular improves drastically.

Charles.

By js55 Engagement 03-22-2007 16:54

Charles, I appreciate the info on the persulphate. The thought occured to me to utilize information technology myself in some manner, especially for HSLA's and the similar.
But in total understanding with you, I had no intent of implying that arc strikes practise non need to be taken seriously. It but that in som alloys they are more than serious than others.

I neglected to add, that I accept often been required to perform hardness tests on the spot during and after the removal.  Information technology is an interesting and revealing operation.  When just ground flush, the spot is often less than RC eighteen.  Then you grind a piddling bit more than, and check the hardness again and information technology goes up to RC 34 to 42.  Than you grind and smoothen it deeper and when you finally get it out, information technology is les than 18 over again.  I take done this during D i.1 Inspections merely to show the welder that he hasn't removed the Arc Strike!

By makeithot Date 03-22-2007 16:39 Edited 03-23-2007 15:34

Joe ,
Correct me if I am incorrect but are not arc strikes considerd a failure of the weld equally a whole. At to the lowest degree in all the tests I have ever taken that has been the case. If in fact the welder does not consider this to exist so, how did he become into the position of having todo a pressure weld to start with? I would like to read the lawmaking that says you can grind them out. If you could postal service that I would like to look it upwards.

By aevald Date 03-22-2007 16:53

Hello makeithot, y'all have a valid point when you say that any exam you always took would not permit any arc strikes outside of the weld articulation on a pressure level examination and as well on many other types of certification tests. Having that occur during the examination is an automatic failure in many cases. You also know that in the real earth situation at that place exists the possibility for arc strikes to happen outside of the joint fifty-fifty when the all-time precautions are taken. I have read other threads that accept discussed this at length and it appears that for the given codes that apply to various situations, at that place are allowances and procedures for the repair of these occurences. Equally ane of the posts on this thread suggested, when the grinding, polishing, and etching showed that the imperfection was gone just the thickness limits were compromised, this was justification for a cutting-out, if the fabric notwithstanding had the proper thickness intact, the repair could exist accepted. Just my take on this. Regards, aevald

By js55 Date 03-22-2007 16:59

I think the danger of arc strikes, as I suggested in the previous mail service varies with alloy. For carbon steels I don't know that there is much justification in documented failures for consideration beyond cracking.
All the same, using hardnesses to demonstrate to welders the effect of arc strikes, fifty-fifty on carbon steels is a excellent idea.

From all that I read in books, regular carbon steels are not supposed to be bothered by accidental arc strikes.  Only I have seen that little hard spot many many many times.  I have also seen the piddling dot caused by an underbead microvoid coalessence (presumably caused by the arc strike), after the arc strike had been footing down considerably!

On one pipeline that I saw, the Brooklyn Union Gas company had a requirement in the tardily forties and early on fifties, that all welders had to weld their marker next to each joint that they welded. One Guy had a big flourished signature, welded most anybody of his joints . "Due east.VanDaly" had a signature that would give John Hancock a complex.

In the middle 90'due south, the gas visitor decided to become rid of all the old spiral wound pipage, because they didn't trust information technology for MAOP that they wanted to go, so they dug it all up and replaced information technology with directly seam pipe.  There were Arc Strikes all over this pipeline and it never blew up due to arc strikes and John Hancocks!

As an inspector on a pipeline project, I allowed the fitter to leave pocket-size pin punch marks (low stress), (used for alignment, during fit upwards,) on the pipe.  The NYS Public Service Commission told me I was not allowed to permit those pivot dial marks to remain.  I had to treat them like Arc Strikes and have the contractor remove them.  The rules also said that the fittings (Els) had to be marked with Low Stress Markers.  The manufacturers also had High Stress markers on the reverse side of the same piece, simply the PSC didn't intendance almost that!

I do not know about failure of the weld as a whole.  (If you meant "Whole")  If youmeant "Hole", I exercise have a series of film slides showing a burn pigsty completely through on the weld metallic on a pipe joint caused by poor contact of the "Antler" grounding device on a xvi inch Cross Country pipeline.

Equally Mr. Hall points out, by and large, I have seen the Amonium Persulfate requirement in Pipline work.  The State Public Service Commission Rules and Federal Pipelins safety rules required this blazon of treatment.

However in NYS Bridge work, the New York State Steel Construction Transmission requires hardness tests for all arc strike removals.

CON-ED besides required it for proof of Arc Strike removal on the within water wall of their power generation boilers.  If you lot left an arc strike on the h2o wall tubes they would fire through in less than a week in some areas of the near impingement zone.

I was upwards on the Alaskan Pipeline in 1974, and the welders were only allowed to have two arc strikes in their lifetime, earlier existence sent down to the lower forty eight.  They had to become back through the Oklahoma Pipe Welders school earlier they were allowed dorsum on the job. (I was not there as a welder, so I did non understand the significance of this at the fourth dimension.)

Should take spent more time learning how to speel. What I meant to say was "whole" not "hole"

Speaking of "prove and tell"...
I laid several pieces of iii/8" flatbar 10 2 out on a table side by side and had one of the welders elevate a 7018 beyond the flatbar pieces actually quickly, and and so had the welder grind them out to his satisfaction. I bent them in my coupon bender and hither is what I showed him....(the piece without the dandy is the make clean piece to evidence the welder that it wasn't the material becaause they were all cut from the same flatbar.)

and a picture upwardly close....

Past aevald Date 03-22-2007 17:49

Howdy John, squeamish pics, definitely show the stress riser effect that could pb to failures. One comment I would like to include here has to do with weld identification by welders on gas transmission lines. I of my welding instructors spent a considerable number of years working for Pacific Northwest Natural Gas, when he first started welding for them they required all welds to be stamped by the welder with his personal stamp. He said that not as well long subsequently that they discontinued the exercise when they started noticing that many of the pipe failures that they were having were due to the impressions made past the stamps. My $.02 Regards, aevald

I have seen that example in one case before when I started out as an apprentice. Nicely done. I feel that it reinforces my conventionalities that an arc strike would exist cause for concern testing or other wise. Brings me back to my original question " Is there an actaul written lawmaking for repiar of arc strikes " If so where? Or is this usually left to the clients discreation as to what is considerd aceptable.

By chall Date 03-23-2007 xvi:00

Search the CFR:  10CFR49 subsection 192.309:  Repair of Steel Pipe.  An arc strike is chosen a paring, and must be repaired if sure limits (defined) are met.

10CFR49 192 is applicable only to gas manual systems.  Someone else will have to chime in for other components.

Charles

By js55 Date 03-23-2007 17:21

makeithot,
I think in answer to your question, at that place is mention of 'repairing' arc strikes in about all construction codes in soime mode or another. Some more than stringent than others. Virtually codes volition write it as a minimum standard in recognition of the fact that the business organisation for arc strikes is very alloy and service dependent.

Past welderwv Engagement 03-23-2007 17:37

TO: jwright650

I teach welding tech at the high schoolhouse level.  I accept heard of this experiment several times but never tried it.  I saw your pictures and decided to attempt it with my advanced class that is getting ready to do state certifications.  I took 4 pieces of 1/2" x ii" apartment bar 6" long and we aptitude one as a control (which bent perfectly).  I had a student drag a E6010, E7018, and MIG across the other samples, we then ground them downward and buffed them to a good appearance and bent them in our guided bend tester.  The results were exactly like yours.  It was an excellent sit-in of the effects of arc strikes.  Thanks!!!

I take seen the furnishings of arc strikes in RT and UT in industry but this is an excellent, unproblematic demonstration that gets the points across.

Joe, only an FYI-
I recently used ammonium persulphate to detect when some unauthorized welding had been completely removed from a bridge girder bottom flange.  It worked very well as far as contrasting weld metal confronting the base metal.(Some bit angles had been welded to the top of the bottom flange to serve as a temporary brace for drain scuppers.  Naturally, that earned some very negative atention from the DOT.  I was asked to help resolve the problem.)

I do non disagree that taking the care you described is a adept idea to get consequent and predictable results.  Even so I did not have much available under field conditions, let solitary any types of scales.
I simply poured some granular ammonium persulphate into a new plastic spray canteen and added tap water until I had what I approximated to exist a 1 to 10 ratio.  I tested the solution on a sample I had made upward.  Temperature was effectually 60 degrees F.  Having read over some very explicit instructions on how to mix up and use the solution, I had some apprehension about it, but it worked fine on the sample.
We used a flapper disk on a iv" grinder which gave a very polish end.  Existence a girder flange, the thought was to remove the accented minimum needed to "make information technology go away". we sprayed on the solution and establish that it was important to go along the treated area moisture - spraying a bit more than as the surface area dried out.
Information technology took most a minute to really see the contrast develop, just when it did the weld metal was clearly differentiated from the base of operations metal. When the solution dried out, a quick spritz made it jump out again.
We were in a homo-lift, on a clomp and chemicals getting in the h2o was a business, then nosotros kept rags effectually and under the test area to capture any drips  and run-off. and besides the rinse solution which was tap water in another spray bottle.

To conclude- the areas were measured as reducing thickness no more than that 0.035", the flange was actually 0.025" average greater than the specified thickness, RT was done on all areas, so DOT was OK with leaving the repairs as is.

Hi Chet

Now I empathize why you lot sprayed it.

As for the exact mixture, it actually has a pretty wide operating range in dilution with water.  Even so, if yous go likewise rich or too lean, it doesn't work at all.  This is a practiced example of how good this etchant is.  I don't know why yous had to protect the h2o in the river.  I bought my bottle of Amonium Persulfate from Fischer Scientific well-nigh 20 years ago.  (At that time they would sell to individuals). The literature at that time, said information technology could be disposed of without any risk precautions.  I tin also recommend a faster acting etchant, that works in any temperature.  Ferric Chloride.  I obtained my Ferric Chloride from a Sewage Handling plant.  They used it in the Water Purification process, so I believe that it can also exist disposed of in the river.

I sure would similar to know how the DOT discovered that the fabricator had used the temporary attachments welded to the flanges!  Where was the inspector!?!?  What DOT was involved?

Joe,
There were some overall environmental concerns with an endangered species that made it much easier to prevent annihilation from going into the h2o, rather than try to explain why no harm would be done.

As far as the mixing ratio, I guessed at it but that was why I used a sample to examination the solution on.  The DOT was on hand to witness the testing before we used information technology on the bridge- and they witnessed the bodily work.  Incidentally, I did consider trying to mensurate the hardness as a means of differentiating weld/base metals but I only had a portable identing tool with microscope (PTC Instruments) and found that everything was less than a RC20.  Weld metallic and base metallic gave below scale readings.

What makes yous call back a fabricator was involved? :)  Actually, it was a field error, the carpenters didn't want to wait to caryatid off the scuppers when they were forming up the deck.  Big oops.  I was asked by the DOT to assistance resolve the state of affairs.  I'm not sure I can divulge the location only it was at to the lowest degree a 7 60 minutes drive one way.

By JA Date 03-24-2007 01:54

so tell me Charles , this "ammonium persulfate".........what is its chief purpose.....?     was this developed for this reason alone , or is it something that only happends to work......?

and thanks for the pics John,,,,,i got to work today,,,,dragged a welding rod beyond a peice of 3/8th,,and pounded it over,,,,,same thing....ripped it right open..........i would have never believed information technology............thanks over again John........

Past chall Date 03-26-2007 12:36

I oasis't the slightest idea what else it is used for, I only found out about it because a customer specified the procedure.

Charles

By jarsanb Date 03-26-2007 15:12

It's an carving solution, used for macroetch'southward. We use this solution along with nital 5% for etches. The amonium persulfate is our choice for arc burns - called out for in state requirements. Nosotros merely use it on loftier pressure inspections > 40% SMYS systems. You will besides find it listed the the AWS destructive & non-destructive testing standard, B1.10 or xi I believe.

By jarsanb Appointment 03-26-2007 17:31

As for depth of repair. Our standards call for maximum removal of 12.five% of the wall thickness. This is an erstwhile united nations-revised requirement. I'm told information technology was a manufactor'southward recommendation. Oasis't checked to see if it comes from the Public Service Commission too or not.

Past js55 Date 03-27-2007 17:22

12.5% sounds remarkably coincident with the 12.5% scheduled pipe thickness manufacturing tolerance.
And you mentioned in the other mail nearly 40% SMYS pressure level service. May I ask, what service that is? Man that's alot of pressure!

Source: https://app.aws.org/forum/topic_show.pl?tid=11293

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