tig nozzle diameter 8

[sixxerxxre]

is there anyone knowing about TIG welding ceramic nozzles diameter parameter ?
what is the result if the welder changes the diameter from 10 mm in WPS to 12 mm or more ? or 9 mm and less ?
is it possible to qualify a TIG weld without recording this parameter ?
thanking you
serge

 

[gtaw]

It is not an essential variable in most American welding standards. As such, it does not have to be recorded.

Best regards - Al

 

[racookpe1978]

Hmmmn.

"Small enough to fit in the space available. Large enough to get enough low-speed shielding gas around the plasma and melted steel to prevent the local wind and wind gusts from disturbing the weld as it cools." ???

 

[kjell123898]

hi sixxerxxe,
we are doing orbital tig welding on super duplex tubing using of 24mm shielding gas nozzles to secure optimal protection from the atmosphere. I'm agree, this is not an essential parameter but by poor gas coverage you will risk oxidation of the weld which in turn weakens the quality as reduced corrosion resistance and strength so I will recommend you to use as large nozzle as possible to achieve sound coverage

Kjell Grønvold

 

[Duwe6]

try using "As Required" for that line in the WPS. And if questioned about [I never have been - 25 years [knocks on wood]], racookpe just gave you the parameters.

Color of stainless welds is how 'adequate gas flow and coverage' is usually checked. If your welding inspector is competent, he/she will be looking at that, and the corresponding cup size, and ensure that a similar cup is used on the much more forgiving carbon steel welds.

 

[sixxerxxre]

thanks to racookpe to answer about influence of parameters
then if is not essential, it looks like not Unimportant.
- in ASME code this is a variable ( not essential ) has it to be recorded in a pWPS ?
- in European standard § 4 of ISO 15609-1 Technical content of a WPS,
§ 4.5.4 mentions as variable : shielding gas flow rate and nozzle diameter.

nozzle diameter has it to be recorded in a welding record to be qualified ?

Duwe6 : thank you, have you any link to take a look on allowed colors on austenitic welds ?

 

[tbuelna]

Here is a sample AWS B2.1 WPS form and on sheet 2 there is a line item for recording nozzle size.

Rather than seeking the path of least resistance with this decision you should look at it from a cost vs. risk standpoint. As racookpe1978 noted gas nozzle size can have an effect on weld quality, so there is some risk involved by not controlling this variable. But it is quick and easy to change a nozzle on a TIG torch to the correct size, so there is not a significant cost burden involved. Thus it would seem to make sense to include the gas nozzle size as a requirement in your WPS.

If you wish to make things easier for your welders by having your WPS allow a range of nozzle sizes to be used, then you might want to perform qualification welds using nozzles at the range of sizes listed just to be safe.

 

[Duwe6]

"Thus it would seem to make sense to include the gas nozzle size as a requirement in your WPS."

Please don't try to tell the welder what cup to use, unless you know as much about the physical act of welding as the welder does. With a broad range of cup diameters and neck lengths, the chances of specifying the optimal combination for any joint are small. The probability of getting it right for a range of groove depths and geometries is nil.

 

[berkshire]

Another variable in this is the use of a GAS LENSE . A device which will allow better gas flow control, allowing greater stick out of the tungsten electrode for welding in tight spaces.
B.E.

You are judged not by what you know, but by what you can do.

 

[sixxerxxre]

hey ! is there anyone to give me any link to take a look on allowed colors on austenitic welds ?
just to verify that the welder took the good diameter...

 

[berkshire]

sixxerxxre,
Ideally there should be no tint on the weld, if your gas purge is good. Most of the tint comes from the fact that the welding nozzle moves beyond the welded area while the metal is still hot enough to oxidize. The degree of this depends on the skill of the welder.
Paradoxically the heat tint is lower with a faster weld, because the metal will melt and solidify at a lower
temperature that will still be covered by the gas shield. the ideal color will be the purple and very light tints at the outer edges of the photo I attached. Very dark scale that is flaking is not acceptable.
B.E.

You are judged not by what you know, but by what you can do.

 

[sixxerxxre]

thank you berkshire
but the photo shows colours on a root and i do not understand what is usually allowed for colour.
on the website i read " This level of colouration is specified in AS/NZS 1554.6 and AWS D18.1/D18.1M:2009 " do you know which European norm tells about what is allowed or not ?
photo 2 on the website shows ( with the red cross ) that the blue colour is not allowed in AS/NZS 1554.6 and AWS D18.1/D18.1M:2009.

 

[berkshire]

sixxerxxre
The second photo is from the Australian welding institute and shows acceptable weld tints on the left up to the line with the red X in it,
And as you can see anything darker than the light straw color is not acceptable. Now this is a section through a pipe where you cannot normally access the inside. The exterior of a pipe can be cleaned with pickling and neutralizing paste if it is allowed by code.
I must point out that this question is a little departure from the discussion on welding cup sizes although they are somewhat related, also most of my stainless experience is in the food service industry, not the nuclear industry where regulations are a little tighter.
I am not up on European welding standards, since I have lived in the USA since 1969, the best I can offer is the attachment below which was new in 2004.
B.E.

You are judged not by what you know, but by what you can do.

 

[tbuelna]

Please don't try to tell the welder what cup to use, unless you know as much about the physical act of welding as the welder does. With a broad range of cup diameters and neck lengths, the chances of specifying the optimal combination for any joint are small. The probability of getting it right for a range of groove depths and geometries is nil.

Actually the WPS is a list of specific work instructions the welder must follow when making a weld that must conform to these requirements. If the welder deviates from the controlled and qualified process described in the WPS then the resulting weld would not meet any QA controls based on conformance to the WPS. That's how modern QA systems work. Develop and qualify a controlled and very detailed process for every manufacturing operation, including welding tubes. And then make sure everyone follows these processes, so that the end product has a uniform, controlled quality.

I work in the aerospace industry, and if any welder were to willfully choose to deviate from a controlled process simply because they felt they might "know better", that welder would immediately be fired. The manufacturing procedure defined in the WPS is the result of inputs from many people including welders, metallurgists, QA experts, stress analysts, fracture control specialists, and reliability experts.

 

[kingnero]

berkshire,
your document shows the correct ideas, but it is dated. new standards are applicable now. If needed, I can give you an update of the correct references.

However, I haven't come across any (european) standard that adresses the allowable amount of oxide or discolouration of stainless.

When necessary, pickling and/or passivation is prescribed.

 

[Duwe6]

". . . QA controls based on conformance to the WPS. That's how modern QA systems work. "
Sorry, but it does NOT. And when we Eng types try for the "1-size will fit all welds, trust me" or the "we know better than you, you unschooled, non-engineering welder" we are FORCING the actual folks doing the actual work to work outside of the tolerances. Because we didn't allow enough freedom to perform the work within tolerance.

Anywhere in a fab shop within 50-ft of a door requires a gas-lens cup to be used, and usually one or two sizes larger than the minimum cup diameter for good gas coverage in 100% still air.
Running argon requires a small increase of the flow for overhead 4G work, and that increase may make the argon flow too fast & turbulent for working on flat 1G work. A deep weld bevel on a pipe at the upper end of the WPS thickness will require a narrower and longer cup than a bevel on Sch10. A large diameter pipe >12NPS [or plate] 'responds better' - gives better heat tint 'color' - than the biggest one that is usable on a 1NPS pipe that is listed on the WPS. Sorry, but these are FACTS. Spend time in the weld shop before you tell professional welders, with pride in their workmanship, how to do their job.

IF the job is repetitive, like joining fuel tubing, all similar [or same] diameter and wall thicknesses in a 'tight' fabshop, then yes you can develop a highly restrictive WPS that can specify the torch gas flow rate at 22-24 scfm, the 'backing' purge gas at 1-3 scfm, and the cup size as a conventional-length #6 w/gas lens, volts = 14, amps 70-78, footpedal amp control not allowed, preflow at 3 seconds minimum, postflow at 5 seconds minimum, each bead to be performed in less than 21-seconds to limit heat input to less than 18,000 joules/inch.
And the way you arrived at these stringent variables was to watch several identical joints being welded and working with them to optimize these variable factors.
Just ain't possible on field work. EXAMPLE: Callaway Nuke plant piping on the reactor coolant loop; about 5 field welds were made, on each of 4 loops. Each set of welds was at a different distance from the construction opening in the Reactor Containment bldg., about 20-ft x 30-ft. Different minimum cup diameters required to handle the unavoidable air movement. Different wind conditions on each day that welding was done on these 20 FW's. As the welders progressed out in the Extended-Land J-Bevel weld prep, the cup diameter needed to increase and the cup length was dropped from long-nose to conventional geometry. Big cup deep in the prep groove means bad visualization of weld puddle, means probability of 'bad' bead that has to be ground out. Too small a cup gives poor gas coverage and the color going from the 'perfect silver & gold' to the 'OK purple' to the 'start grinding grey' to the 'your fired as a welder scaly grey-black.' Depending on the day's temperature, the amps used on the Automatic GTAW dwell on the sidewalls had to be adjusted up and down significantly to compensate for the basemetal temperature and heat loss between beads. Cold outside = weld slightly hotter to compensate, and to maintain a nice 'hot' bead with toe angles of 120° or better. Then the weld cap requires a different travel speed and filler feed rate, with different amps and volts, highly dependent on the base metal temp. It makes a big difference if the 304 pipe is at 55°F or 340° when trying to make a beautiful cap. And these guys got two tries at it. We ran two welding crews on the loops, and eachweld was unique, so 1 weld to 'learn on' and one more to do, than the that phase of heavy-wall stainless welding was OVER. For a 6-year $1.2B project. Yes these welds had been mocked-up, in a shop with only a foot or three of pipe attached. So the mock-ups were very similar to reality, but they were not 'reality'. Each highly-critical weld was slightly different, each welder had slightly different techniques to achieve superb results, temperatures differed, etc. Nothing was identical, thus a 'tight' stringent WPS would never have allowed excellent work to have been done on each of these 20 welds. The WPS was 'snug' and we had to trust the welders to change with the changing conditions.

 

[berkshire]

Kingnero,
Like I said in my post , I knew it was old when I put it there, but it was the best I had, and was to give the OP an idea of where to start looking.
Duwe6,
Your entry tells it like it is.
sixxerxxre (Nuclear) (OP)
You have to get qualified welders on your job, give them your WPS, and see that they are capable of working to it, then give them enough flexibility in the WPS that they can adapt to changing conditions, and give you an acceptable joint.You also need to learn what an acceptable joint is.
You also need to give the welder the flexibility to stop work, if the parameters for a good/safe weld are exceeded, such as, but not limited to, some idiot opening the shop door on a windy day.
B.E.


You are judged not by what you know, but by what you can do.

 

[DekDee]

Duwe6,
As an ex pipe-welder who has progressed into Quality management I couldn't agree more with your post.
However, I do have to query this comment.

"Different minimum cup diameters required to handle the unavoidable air movement. Different wind conditions on each day that welding was done on these 20 FW's."

I mainly work LNG now and every GTAW weld performed in the field must be performed inside a sealed enclosure (we call them weld tents or "humpies").
Strange to see super critical welds in a Nuclear Power Plant being performed in conditions open to the environment.

Cheers,
DD

 

[Duwe6]

The air at the Reactor Coolant Loop welds was reasonably still. There was very large equipment, lots of pipe and conduit and one concrete shielding wall between them and that huge construction opening. But it wasn't as still as in a nice 'hooch' closed tent on a pipe out in a field. On a pipeline, the next weld if 40-ft from you, which in construction is a big distance. There was an entire nuke plant to build, and closing off those areas for the 3½-days of continuous welding that it took to make these joints was just not possible. If there was a breeze, the guys would put up a tarp or sheet of plastic to block it, but they couldn't make the work all around them stop for the month to 1.5 months it took from the first tack on the first weld, until the last weld passed X-ray. The work goes on, and the welders have to figure out how to deal with it, while still making welds that look like jewelry.

 

[tbuelna]

Duwe6-

I think we are considering different issues. I agree that the input from an experienced welder is invaluable when developing and qualifying a WPS. It is also a good idea to provide as much flexibility as possible with the requirements contained in a WPS, including variables such as cup or nozzle size used. But if the work instructions provided (ie. the contract SOW, PO, engineering documentation, etc.) state that the welding shall be performed in accordance with WPS XXX, then WPS XXX must be followed.

The OP asked two questions. The first question asked about the implications of a welder unilaterally deciding to use a 12mm (or larger) or a 9mm (or smaller) diameter gas nozzle rather than the 10mm nozzle specified in the WPS for the weld. The answer is that since the welder did not follow the guidelines contained in the noted WPS then the weld is technically non-conforming, and it should not receive QA approval. Part of the job of on-site QA inspectors is to verify that the requirements in a WPS are complied with. This would include verifying that the specified type of equipment is used, including a certain size gas nozzle if required by the WPS.

The second question in the OP asked if it is possible to qualify a WPS without including a requirement for gas nozzle size. The answer is yes it is. While a welder should never decide on their own to deviate from a controlled process requirement like a WPS, there are ways the welder can get approval for deviating from the WPS. One way is to submit an ECR asking to revise the WPS. Another way is to have QA submit a DR to engineering/MRB asking them to approve the non-conforming welds.