welding from one side
welding from one side
(OP)
Need to do some fracture-critical welding with access only from one side of the weld once both plates are in place. Tensile stress across the weld, so can't use stay-in-place steel backing (which would be welded to one side of the joint before the plate is put into place, if this weren't a tension connection).
Thought about ceramic backing (and qualification per AWS D1.5 section 5.7.7), but is there a version of ceramic backing that doesn't require access to both sides of the joint in place? The only stuff I've seen involves a strip of tape that runs across the ceramic and tapes to both sides.
If not, AWS D1.5 section 5.7.7 allows qualification of PJP as CJP even without any backing at all, I think. There's a bend test & macroetch to demonstrate adequate fusion & penetration at the root, but wouldn't melt-through still be a fatigue concern? (Or is the no-backing case blocked by other provisions of D1.5 such as 4.6.9 and 4.7.6?)
Hg
Thought about ceramic backing (and qualification per AWS D1.5 section 5.7.7), but is there a version of ceramic backing that doesn't require access to both sides of the joint in place? The only stuff I've seen involves a strip of tape that runs across the ceramic and tapes to both sides.
If not, AWS D1.5 section 5.7.7 allows qualification of PJP as CJP even without any backing at all, I think. There's a bend test & macroetch to demonstrate adequate fusion & penetration at the root, but wouldn't melt-through still be a fatigue concern? (Or is the no-backing case blocked by other provisions of D1.5 such as 4.6.9 and 4.7.6?)
Hg
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RE: welding from one side
I have a little trouble in following the terminology you reference in your post. Can you qualify the weld joint as CJP using a consumable insert with a single-vee weld prep?
RE: welding from one side
http://www.welding-advisers.com/
RE: welding from one side
Al
RE: welding from one side
PJP vs. CJP sounds like a design issue.
RE: welding from one side
A simplified description of the structure would be built-up box (not big enough to put someone inside even if we could get them out after welding) with diaphragms. And welded field connections.
Once the joint is assembled, can't get to the back--not to put in a root pass, not to tape on ceramic, not to backgouge, not to remove backing. I didn't immediately see another way to design the structure to avoid this (I'm not the designer but I have some input), but I'll look again when I get my hands on the plans again tomorrow.
I am completely ignorant about consumable inserts. Rather than bug y'all with all kinds of stupid questions, where should I look to get some basic information so I know whether to recommend this option? (The fabricator is still responsible for knowing what they're doing; the fate of the welding is not in my hands.) Has anyone used a consumable insert on a D1.5 job?
Hg
Eng-Tips policies: FAQ731-376
RE: welding from one side
RE: welding from one side
From your description you could flood the cavity with Argon as a back purge when welding the consumable insert.
RE: welding from one side
There was a "Megastructures" Problem mention that the Navy has a new procedure for welding thick section from one side that claimed to do a better job that the older welding procedure. The programs description of the welding procedure left a lot to desired.
RE: welding from one side
Best suggestion I've received so far is to leave the designer on the back side of the weld with a flashlight and a file. Except that the space is too small.
We're probably looking at a redesign in some areas, and where they can't do that, go back to the fused steel backing and design for a Category D or E detail...there's just simply no way in a bridge application to do a one-sided weld without some kind of notch on the back side, whether it's potential lack of full penetration, effects of melthrough, or the actual notch created by the steel backing.
Or get some Aethyopean bolt tighteners and teach them welding...
http://tinyurl.com/5p87r
(Paul Pendragon, Process Engineering magazine, 1973)
Hg
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RE: welding from one side
Gerald Austin
Iuka, Mississippi
http://www.weldinginspectionsvcs.com
RE: welding from one side
http://se
RE: welding from one side
Hg
Eng-Tips policies: FAQ731-376
RE: welding from one side
I may be looking at this too simplistically but based on your original post why can't you simply have a grinder secured to one end of a pole that can reach around the back side of the inaccessible weld joint and locally back-grind the full penetration weld to reduce stress concentration?
RE: welding from one side
It is more difficult on Tee joints than butt joints but still possible.
Gerald Austin
Iuka, Mississippi
http://www.weldinginspectionsvcs.com
RE: welding from one side
I think they can put access holes in some locations, at least enough to get an arm in to apply ceramic backing, and possibly enough to just go in there and grind. For example, on the box splice, they could weld the fascia side with access from inside the box and then do something bolted on the non-fascia side. Not that I've heard anything yet about them actually planning to add any access holes, but it's at least a possibility.
But I think there are still some welds we just won't be able to get access to.
pipewelder--the question is whether open root welding can be performed that doesn't effectively create a notch or similar effect on the back side of the weld. We're working within AWS D1.5 though I see some noted exceptions headed our way fast...
Hg
Eng-Tips policies: FAQ731-376
RE: welding from one side
Have you considered making up some mock up assemblies and trying out your options? It may be the best way to determine which track is the best to take.
RE: welding from one side
Hg
Eng-Tips policies: FAQ731-376
RE: welding from one side
RE: welding from one side
Asking around among bridge people, though, no one seems to believe that there's any kind of one-sided welding that wouldn't be considered to be a Category D or E fatigue detail.
And the design consultant doesn't have a welding lab...
Do they make non-pipe consumable inserts? How does the backside of a typical such weld compare to the backside of one made against ceramic backing?
Hg
Eng-Tips policies: FAQ731-376
RE: welding from one side
A preplaced consumable insert would not lend itself to being easily welded in a plate tee joint configuration if the root side contour needed to be controlled and the re-entrant angle of the weld toes small .
You could contact someone at imperial or some other insert supplier to see if they have any ideas . http://www.imperialweldring.com/
Gerald Austin
Iuka, Mississippi
http://www.weldinginspectionsvcs.com
RE: welding from one side
Here is all types of ceramic backup tapes. The only problem is that I can't find a US distributor, only the Netherlands. You might Email, you have a good address, the company and see if they have a US distributor.
It looks like they have all angles covered under the three headings. Especially look at CBM 8601(4G).
http://www.dicera.com/eng/e_main.html
http
RE: welding from one side
The good thing about fused steel backing is that it can be tacked to just one side before the joint is assembled and the connection is rigid enough that the other side doesn't have to be tacked.
Meanwhile, back on the ranch, the Fabrication Consultant Dude says that he doesn't think bridge applications have good enough fitup for a consumable insert to work.
Hg
Eng-Tips policies: FAQ731-376
RE: welding from one side
The just of the discussions were the use of a inserts and backing plate of various sorts from a Z bar to flux coated Cu and Steel. Most used a backing bar with a groove and if possible purged the backside of the weld through the groove. I’m still try to get some information from another yard that works on good old big ones.
Here is an article from the UK concerning similar situations in respect to fatigue. Starting about page 60 there are some joint descriptions that might be of interest. .
http:
RE: welding from one side
AWS D1.1 does not consider any weld joint, welded from one side with backing, that is not steel to be pre-qualified. welding with copper backing, ceramic backing, etc.will require procedure qualification.
RE: welding from one side
billMcL--this is a D1.5 job, so nothing is prequalified. But this wouldn't even fall into the category of standard qualifiable joint, and I'm hesitant to let them qualify it as a nonstandard joint based on a single test plate that doesn't include any fatigue testing.
I'm a big fan of the "avoid the situation" technique myself. Now that the situation's here, I think what they're going to do is size everthing for some godawful fatigue category. Still waiting to hear about that...
Hg
Eng-Tips policies: FAQ731-376
RE: welding from one side
In addition to and on the lighter side.
Talked to my oldest (96 yrs old) source this morning and just for curiosity asked him about one side welding of thick materials, say 2.5".
"His comment was get you some good pattern pine 2x4's as backup along with a large torch and asbestos shirt, sleeves and balaclava.
The pine 2x4's were very dry long leaf yellow or white pine.
The torch he was speaking of is a twin carbon arc running about 400 to 500 amps at 60-90 volts using a 1/4" bare rod. He said hook two “pigs” togather with the voltage set at max.”
He also said that he didn't envy you your job based on some of the fit-ups he had seen on some local construction. He also told me to tell you to practice "CMA".
RE: welding from one side
I'd have a lot more whining to do, just for whining's sake, except that this is a public forum. CMA.
It'll all work out in the end. 10 years from now everyone will be happy.
Hg
Eng-Tips policies: FAQ731-376
RE: welding from one side
Could you possibly post the material specs on your job?
RE: welding from one side
One of the several reasons tubular members aren't in D1.5 yet is exactly this issue of one-sided welding. (Not that I have HSS in this project but it's a similar issue.)
And yet there are fancy signature spans out there with tubular members, like those French bridges with the corrugated webs coming down to a single tubular member in place of the bottom flange, or that AISC poster child with the big red freestanding tubular arches (some of you probably know what I'm talking about).
Oh, here it is:
http://www
Damen Ave. Bridge, Chicago
The article doesn't say how they spliced it, but the arch is probably in compression anyway.
Hg
Eng-Tips policies: FAQ731-376
RE: welding from one side
Tubular Structures
https:/
An expensive one. Look at part nine. It would be nice to take a peek. There should have been another conference since this one.
This book is on Google Books.
https://
Pickuped on these books while looking for another book.
I still have several queries out on you problems.
RE: welding from one side
ht
http://www.ooae.org/omaedatabase/omae00dbmat.htm
If you have access to Metadex It would be a good place to start looking for a presentation if not available from the presenting organization.
http://www.csa.com/factsheets/metadex-set-c.php
Take care as you will see in both organizations the word arctic is quite prominent. It was common knowledge when I started work that if you didn’t solve the problem they would send you to Alaska. Just be careful or you might end up working on Senator Steven’s big bridge to nowhere.
RE: welding from one side
For my project, they decided to go with access holes for some of the welds, and redesignating others as non-tension welds (or low enough tension that bad fatigue category was okay, or something).
Hg
Eng-Tips policies: FAQ731-376
RE: welding from one side
I guess it doesn't pay for me to think. That thread had me worried, how can you put rat holes at critical joint.
PS
I haven’t heard from my big city buddy about what he has ran into with fabrication problems similar to yours. I think he has been involved with some lift failures.
RE: welding from one side
Hg
Eng-Tips policies: FAQ731-376
RE: welding from one side
I have just been appraised of a very similar situation where some components were welded out of sequence and have possibly created a very expensive problem.
RE: welding from one side
Hg
Eng-Tips policies: FAQ731-376
RE: welding from one side