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Up Topic Welding Industry / Inspection & Qualification / SMAW instead of GTAW for root pass for Process Piping
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- - By Richman (**) Date 07-27-2009 04:05 Edited 08-14-2009 10:11
Why most of the root and second pass of girth butt welding and other branch connection welds where full penetration is required for many GAS plant project I had worked, GTAW (TIG) SHALL be used rather than SMAW process especially for Process piping like for STAINLESS Steel, in all NON FERROUS ALLOYS, AMINE, CAUSTIC lines, WET H2S and for LOW TEMPERATURE SERVICE below O degree. What are the advantages and disadvantages or the specific purpose of using GTAW (TIG) on root and second pass on the above sample PIPING PROCESS AND SERVICES?
Parent - - By aevald (*****) Date 07-27-2009 06:56
Hello Richman, the thought process might go something like this: GTAW is a very "sanitary" process, meaning there is no slag to contend with and generally the tie-ins at the toes of the root pass and starts/stops are very clean as well. Precise and sanitary is the key with GTAW. If you have an opportunity to look at a properly placed root pass performed with GTAW it will look as if someone had welded it from the inside. That is providing that proper purge or other forms of internal protection are provided for the root and it is maintained long enough for the heat from additional passes to be negated and not oxidize or otherwise contaminate the root surface. I would say this the main reason for specifying a GTAW root and hotpass. Best regards, Allan
Parent - - By jon20013 (*****) Date 07-27-2009 07:20
Nicely said Allan, adding all of these things add up to maximizing the chances of passing RT or other NDE.
Parent - - By 803056 (*****) Date 07-27-2009 14:17
As is typical of all of Allan's responses, he hit most of the important points.

The only thing I would add is that some systems can not tolerate slag on the root side of the pipe. Allen mentioned "sanitary" systems, but even for systems that are not for sanitary conditions, slag may be a problem. Slag can and will break away  from the weld over time. It will enter the fluid stream and can cause equipment malfunctions down-stream. Internal root protrusions can also interfere with cleaning operations if they are "bad" enough.

I had a job to witness the repairs on a sour gas pump that was destroyed by a piece of weld wire and slag that broke free of an up-stream weld. There was suppose to be a screen installed on the up-stream side, but as luck would have it, it was installed on the down-stream side of the pump by mistake. They said the new pump lasted less than a minute or two before the debris entered the pump and shattered the casing and damaged the impeller. A very expensive mistake.

Best regards - Al
Parent - By Revjsnizzle (**) Date 07-27-2009 15:33
Another problem with slag is that once it does brake free, if it happens to miss damaging anything, unlike in 803's example, there is a very high liklyhood that where the slag was is going to be a area of increased corrosion and possible weld failure in the future.
Parent - - By swsweld (****) Date 07-28-2009 03:39
Good points by all as usual. Internal cleanliness is a concern on most systems. Some much more than others. In some systems the pipe ends will always be covered until the fit is made and QC will verify that nothing enters the pipe system until the root pass is made. The last nuclear plant shut down I worked on, a fitter accidentally dropped a piece of TIG wire into the pipe. (2G) Everything stops until the (FOSAR) Foreign Object Search And Retrieval team retrieves the wire.

Recently we were directed (by the specs) to use backing rings for the underground chill and hot water pipe systems at Fort Bragg. Up until two years ago it was required to make the welds open butt. The recent change was because the bee bees (internal splatter) accumulated enough to clog strainers and damage some pumps. If you have 500-1000 welds the bee bees add up.

The WPS will determine if the hot pass is SMAW or GTAW but if the procedure is (very common) a TIG root/hot and then stick it out, the main reason that the hot pass is TIG is so that you do not blow through the root pass. SMAW on top of the TIG root can be done without blow through but it is more risky.
Parent - - By Joey (***) Date 07-29-2009 09:55
You may refer to API RP 577

5.3.1 Advantages of GTAW

Some commonly accepted advantages of the GTAW process include:

a. Produces high purity welds, generally free from defects.
b. Little post-weld cleaning is required.
c. Allows for excellent control of root pass weld penetration.
d. Can be used with or without filler metal, dependent on the application

5.3.2 Limitations of GTAW

Limitations associated with GTAW process are:

a. Deposition rates are lower than the rates possible with consumable electrode arc welding processes.
b. Has a low tolerance for contaminants on filler or base metals.
c. Difficult to shield the weld zone properly in drafty environments.

Regards
Joey
Parent - - By js55 (*****) Date 07-29-2009 16:36
A couple of things if ya'll might allow me to be a fly in the ointment.

GTAW will only provide 'purer' welds if the base metal is pure. Its higher dilution from the base metal means that it may very well provide dirtier welds than say GMAW SC with less dilution since GTAW will draw more impurities from the base metal. Though GMAW SC will still have greater oxides of course.

Another thing, I think that ensuring more success with RT has a proviso. GTAW requires greater skill given that its a two hand process. This greater skill requirement would argue that improved RT performance might be counterbalanced.
GTAW lends itself to auto/machine applications which SMAW doesn't and this can certainly lead to greater RT success.
Parent - - By Richman (**) Date 07-30-2009 13:43 Edited 07-30-2009 13:46
Which is more stringent the Specs or the WPS. I encounter in one project the engineer allowing subcontractor to use WPS using SMAW on root pass with back welding verbally( no documents were signed) instead of GTAW while it stated on the specs that any girth butt welds for Austenitic Stainless steel piping shall be made by GTAW process.
Parent - By swsweld (****) Date 07-31-2009 04:22
Typically the specs rule. The specs should state the code, process, material class, etc and usually requires welder certifications and WPS to be submitted to the engineer for approval before welding begins. After the WPS is approved by the engineer then the WPS is as stringent as the specification that required it. I'm sure that deviations from the specs are common but they should be signed, verbal authorizations are ticking time bombs.
Parent - - By 3.2 Inspector (***) Date 08-02-2009 16:33
"GTAW requires greater skill given that its a two hand process."

Ehm....really?
Parent - - By swsweld (****) Date 08-02-2009 18:24
I definitely agree that GTAW requires the most skill.

1. GTAW
2. SMAW
3. FCAW
4. GMAW

IMO that is the order of difficulty for the basic processes on a groove or fillet weld.
Parent - - By 3.2 Inspector (***) Date 08-02-2009 18:53
Are we talking about the same GTAW here?
You guys can't be serious that GTAW (tig) is very difficult, not to say that everybody can master it.

It is IMHO the most easy welding method by FAR....

Oh well

3.2
Parent - - By 803056 (*****) Date 08-02-2009 23:08
I can't help myself, I have to ask the question, "Are you a welder or have you ever been a welder?"

Trying to weld with GTAW in the field, where you are in an awkward position or at best in the standing position, without the benefit of a foot pedal to control the amperage, was without a doubt the most difficult welding process I ever had to contend with.

When compared to SMAW, GMAW, FCAW, or SAW (I've held certs in each of them), GTAW was by far the most difficult welding process to master.

Best regards - Al
Parent - - By 3.2 Inspector (***) Date 08-03-2009 07:26
Al,

Yes I have been a welder myself on boilers worlwide for almost 10 years. Now I am the inspector.

"Trying to weld with GTAW in the field, where you are in an awkward position or at best in the standing position, without the benefit of a foot pedal to control the amperage, was without a doubt the most difficult welding process I ever had to contend with"

No offense here Al, but in Scandinavia we do not use foot pedals to control amperage (lol) we have it buildt in to the torch, or some people simply chose to "click" to control the amperage. I cant even imagine to be in the boiler roof with a foot pedal.

As I said, it is easy to learn, but not everyone can master it.....the use of mirrors, etc....

3.2
Parent - By Lawrence (*****) Date 08-11-2009 17:28
3.2

Field welders in the U.S. also use torch/thumb controls on tig torches  :)   They have been around for about 25 years or so.

I would agree with others that GTAW is a bit more of a challenge for a beginner to learn.

This is not a dig on SMAW welders who perform all position open roots.  Those can be as hard as any GTA weld, prolly harder.

But for all around training purposes.. I would say most beginners require more time to master basic GTAW than any other process.. Just my observation as a teacher and a learner  :)
Parent - - By Shane Feder (****) Date 08-02-2009 23:11
3.2,
I hope you are not in one of your stirring moods.
I was an ASME IX qualified pipe welder for 17 years using GTAW, SMAW, FCAW and GMAW on carbon, stainless, duplex, chromolly and titanium and GTAW is definitely the most difficult of the four processes noted.

This is taken directly out of the CSWIP 3.1 Welding Inspectors Course Notes.

11.8 Disadvantages of the TIG Process
"There is need for higher dexterity and welder co-ordination than with MIG/MAG (GMAW) or MMA (SMAW) welding."

Regards,
Shane
Parent - - By Superflux (****) Date 08-03-2009 06:03 Edited 08-03-2009 06:09
3.2,
Not all welding locations are created equal.
I had a friend who worked manufacturing S/S toilets and sinks for prisons. Bright, clean A/C shop, foot pedal, wore nice clothes...
Nothing compared working an outage trying to screw your body into the economizer of a 750 MW Boiler 250' in the air, with a dry rig tig and a brain-dead helper laying on the next scaffold with his I-pod ear buds blaring. If you have been in this position, can please tell me how this is easy. I'm not being a smart aleck here. Just want to prey upon your mastery and expertise so the next time l can make it go smooth on myself.

BTW, that previously mentioned shop only pays $9.00/hr
Parent - By 3.2 Inspector (***) Date 08-03-2009 07:33
Super,

Yes, I have been in that position, for the past 20 years (10 as a welder, and now 10 as an inspector)
Would you rather weld in the economizer with SMAW?

I'm not being a smart aleck here. Just want to prey upon your mastery and expertise so the next time l can make it go smooth on myself.

Dude, dont get confused here....and you will be OK

3.2
Parent - - By 3.2 Inspector (***) Date 08-03-2009 07:36
Shane,

No stirring mode here....
I know what TWI say about Tig welding, make you wonder about the quality of their courses :)

If I remember correct the CSWIP 3.1 notes also has information about advantages of Tig.

3.2
Parent - By Shane Feder (****) Date 08-03-2009 09:26
3.2,
An opinion is never wrong - and if your opinion is that TIG (GTAW) is the easiest process then so be it.

But I will eat my "Kromer" (the one I haven't worn for 13 years) if you can find a single person on this forum (or any other forum) who actually agrees with you.

Regards,
Shane
Parent - - By ssbn727 (*****) Date 08-03-2009 10:12
3.2,

Please tell me what do the Advantages of GTAW or as you prefer to describe it as TIG - have to do with the fact that the manual skill level requires a greater amount of dexterity, and welder co-ordination than with MIG/MAG (GMAW) or MMA (SMAW) welding? I look forward to your response. ;)

Respectfully,
Henry
Parent - - By 3.2 Inspector (***) Date 08-03-2009 10:41
Nothing....

I have seen your GTAW machines, and fully understand that its a pain in the butt to use :)

3.2
Parent - - By js55 (*****) Date 08-03-2009 12:30
It is amaziong sometimes how something so obvious has so much trouble achieving unanimity. Though we have a pretty strong consensus. The manipulation of one hand or the other, with GTAW, has to be subconcious and requires time to accomplish. We ain't talkin beads on plate here. GTAW is called upon for root passes most often and therein is the difficulty.
Parent - - By 3.2 Inspector (***) Date 08-03-2009 12:37
Are you saying that a root pass is difficult with GTAW?
You barely have to move your "second" hand.

Well, IMO it is very very easy to learn, and requires little skill to weld 2 pieces of pipe together, without defects.

No offense to any welders who might have problems with it, but it is my honest oppinion that it is very easy to learn.

For obvious reasons things becomes more complicated when you are welding in confined spaces and maybe have to look at a mirror, but that is the case with any kind of welding.

3.2
Parent - - By jrw159 (*****) Date 08-03-2009 12:39
3.2,
   So you are saying that it is easier to learn the GTAW process than the GMAW process???

jrw159
Parent - - By 3.2 Inspector (***) Date 08-03-2009 12:43
My bad....

For some reason I thought we talked about pipe welding, whichis subject to various kinds of NDT.
I agree 100% that any monkey can run a GMAW bead on a random piece of plate, no question about that.

3.2
Parent - - By jrw159 (*****) Date 08-03-2009 12:48
No, no... pipe was the subject, and I may be guilty here of not mentioning that in my response. However, just my humble opinion combined with my past experience both with myself and other welders, be it pipe or plate, GTAW is more difficult than GMAW.

If you have found this to not be the case, again, I salute your level of skill. It is not that way with the large majority.

jrw159
Parent - By 3.2 Inspector (***) Date 08-03-2009 12:58
No need to salute my skills, as I dont think it require any :)

3.2
Parent - - By js55 (*****) Date 08-03-2009 13:01
Things become more complicated when gaps are not ideal, when landings vary, or more so, when you have a landing on one side and a feather edge on the other, when ID mismatch is less than ideal, or all at the same time.
Cellulosics (most common when roots are with SMAW) and GMAW (especially) both handle these variances easier than GTAW.
Parent - By 3.2 Inspector (***) Date 08-03-2009 13:02
I don't agree.

3.2
Parent - - By jrw159 (*****) Date 08-03-2009 12:36
Henry,
  I was wondering the same thing. This went from what is easier to learn and use to what is the better process. Well I will say as for what is the better process, that depends on alot of things that have yet to be mentioned. What is easiest to learn? Well of course GMAW!!!

Now for those that feel GTAW is the easiest to learn, I salute your skills because the remaining 99% of the welding community will disagree. You can teach a dyslexic monkey to use the GMAW process. Not so much with GTAW. :-) 1 out of ten might say otherwise, but that 1 is one of two things, very talented or completely lost.

For me personally hardest to easiest would be in this order.

GTAW
SMAW
FCAW
GMAW

jrw159
Parent - - By bert lee (**) Date 08-03-2009 16:15 Edited 08-03-2009 16:20
in my place, good GTAW welders are ladies, they are assigned to weld the root and hot passes only.
the rest will be welded by men using SMAW for pipe.

before employing them, we asked them if they can weld using SMAW or other processes? but they prefer GTAW (TIG) only.
anyway, we also hired them (4 ladies) just for root pass and hot pass and for those below 3"dia pipe. i must say that they are good
less rejection compare to male welders.

i do believe that you can only say it the most easy, when you are using the same welding process all the time.

we have a welder assigned to weld overhead welding most of the time, and when he took the 3G test, he failed.  

in states, you normally drive a car in left hand and its easy because you are use to it.....but when you go to Malaysia or Indonesia you will have difficulty
because it is in right hand drive. i think this example also applies to welder when choosing the easiest process for him/her.

bert
Parent - - By jrw159 (*****) Date 08-03-2009 16:35
I guess I am looking at it from the standpoint of a beginning welder/fresh slate who has no experience in any process. Setting aside all the other factors, the majority will have more trouble with GTAW than the other processes. 

Now when looked at as you are, yes, what a person is most used to will obviously be the easiest for them. This makes perfect sense.

jrw159 :-)

Parent - - By bert lee (**) Date 08-03-2009 16:51
GTAW & SMAW welders are mostly use in oil/gas piping whereas FCAW & GMAW welders are for heavy structures

try to employ welders from oil and gas and bring them to heavy structures using FCAW & GMAW..i will be suprised if they don't grumble or complain.

bert
Parent - - By jrw159 (*****) Date 08-03-2009 16:59
Bert,
  I know many welders from both fields and you are correct, they for sure would grumble, but it would not be because they had trouble going from GTAW & SMAW to GMAW & FCAW. It would be grumbling about the cut in pay for going from GTAW/SMAW to the two easier processes of GMAW/FCAW. There is a reason pipe liners/ get more for GTAW/SMAW. This is because they are harder processes to master.

As an example, I have tested welders from the oil and gas industry in our shop that utilizes GMAW/FCAW and they did great with these processes. However, when told the going rate of pay for these process,.... well lets just say they do not work here.

jrw159
Parent - - By bert lee (**) Date 08-03-2009 17:18
believe me same pay, the reason i received is very tiring and not use to welding gun of FCAW & GMAW.

bert
Parent - - By jrw159 (*****) Date 08-03-2009 18:24
Bert,
  You may have mentioned in the past and I did not catch it, but where abouts are you from? I can see the possibility of the tiring and not being used to it, but I am hard pressed to think of any area I know of that pays more for GMAW & FCAW. That does not mean that is does not happen, it's just not typical.

jrw159
Parent - - By bert lee (**) Date 08-04-2009 14:52
thanks for response.

i'm from indonesia and working around asia.
it really happen here, aside from qc work my boss also delagated to me the selection
of welders.

the labor cost will depends on where the welders come from.
Filipinos is ideal for oil and gas piping but expesive compare to Bangladeshi welder...imagine they may have same level of skill but with different cost.

bert
 
Parent - By jrw159 (*****) Date 08-04-2009 15:14
Bert,
  I see. Those are areas I have no knowledge of pay scales.

jrw159
Parent - - By ssbn727 (*****) Date 08-03-2009 16:39 Edited 08-03-2009 20:47
Hi John R. West!
As a welding instructor with over 15 years experience, I agree with you, and I'm still interested in reading a straightforward answer to my question from 3.2 because, I know that the question I posed to 3.2 was not answered - simply put!

Do you think it might have something to do with the very high quality rum, and now that I mentioned those particular spirits as well as being a retired professional drinker with a wide enough amount of exposure to various grades of rums from different countries; the best rum by far was the original Cuban rum made by the Bacardi family although there is some rum made in the Dominican Republic that came in a close second such as the Bermudez brand's limited reserve... Certain Jamaican Rums did give it a run for it's money back when I was still a professional drinker (heck! If 3.2 can change the subject, then so can I!). However since my retirement, I can no longer back up my claims as an expert. ;) ;) ;)

Getting back to the topic with regards to this thread... An Austrian company has come up with both an automatic, and a semi-automatic version of manually held GTAW/TIG torch mechanism that incorporates an improved version of being able to feed the filler metal into the location where the torch establishes the weld pool either as cold wire fed or hot wire fed as this technology has been around, and available for quite some time now... However, this system is designed so that if one were to use it for pipe welding then, only one hand would be required to weld with it!!! :) :) :)

In fact our old friend Ed Craig is pushing this system through his website, and will be available for commercial use tentatively after =July 1st, 2009... The system is called "TIP - TIG and here's the links to this advancement of an idea that's been around for quite some time already:

http://www.youtube.com/user/TIPTIG

http://www.weldreality.com/TIP-TIG-Welding.htm

http://www.weldreality.com/TIP-TIG-welding-information.htm

http://www.plasch.at/

Over one thousand companies are using this system in Europe already... Here is one of the lesser known French models:

http://www.elektrosta.com/gb/pages/01.html

Here's onr from Italy:

http://www.trafimet.com/Ing/Prod_23.html

These are some of the cold & hot wire systems for both semi & fully automated applications that have been available here in the states for quite some time:

http://www.ckworldwide.com/coldwire.htm

http://www.jetline.com/product.aspx?i=14525&c=30&pp=8&sb=0&p=0

http://pdf.directindustry.com/pdf/jet-line-engineering/cold-wire-tig-feeder/27577-35521.html

http://www.ap-automation.com/products/tig-wire-feed/

This torch is from Fronius (I wonder how Stephan is doing these days?):

http://www.welder.by/files/TTW_4000_KD.pdf

http://www.ametinc.com/brochures/AMET_XMS-HWT.pdf

Here are some turnkey robotic systems available:

http://www.integrated-robotics.com/PDF_Files/Robotic%20TIG%20Welder.pdf

http://www.motoman.com/products/welding/plasma.php

http://content.lincolnelectric.com/pdfs/products/literature/e10300.pdf

http://www.reisrobotics.de/reisrobotics/us/APPLICATIONS/Welding+technique-p-124/Tig+welding-p-365.html

Some cool stuff here:

http://www.blueshield.ca/en/docs/pdf/marketingInfo/brochures/PlasmaTigTraining_E.pdf

Here's a plasma TIG torch that could be used in conjunction with the TIP-TIG system in order to improve on the arc characteristics especially when welding certain pipe metal alloys:

http://www.water-joint.com/e/swf/pt_teile.swf

So is this what you're referring to 3.2?

Enjoy the reading folks!!! :) :) :)

Respectfully,
Henry

Parent - - By 3.2 Inspector (***) Date 08-03-2009 16:46
I gave you a reply, here it is again "Nothing"
Are you sure that you stopped drinking?

3.2
Parent - - By ssbn727 (*****) Date 08-03-2009 17:08 Edited 08-03-2009 17:33
I expected as much of a reply from you 3.2... :)

I retired as a professional drinker of alcoholic spirits seventeen years ago if you really must know so, please act as if you are a practicing professional 3.2 because, you're certainly doing a lousy job of it so far and I believe everyone in here would agree with me in my observation as well as their own previous observations also.

In other words: GROW UP!!!
Parent - By 3.2 Inspector (***) Date 08-03-2009 17:13
You are free to think whatever you want :) and so am I.

3.2
Parent - - By jrw159 (*****) Date 08-03-2009 16:49 Edited 08-03-2009 16:51
Henry,
   LOL, Yes indeed they produce THE BEST rum! :-) As for an answer to your question, I would also like to hear how it takes less skill and dexterity, coordination ect. to learn/use the GTAW process as opposed to the others. Not going to hold my breath to hear something that makes sense though. I have taught just a few (very few in comparison to you) welders to use all four processes and have yet to have one master GTAW before GMAW.

I have seen a little about Tip-Tig but no where near the amount of info you have provided. I will be busy for awhile with this, thanks. :-)

jrw159

EDIT: I see I was correct in not holding my breath. :-)
Parent - - By 3.2 Inspector (***) Date 08-03-2009 17:02
I simply think GTAW is a "safer" way to weld pipes subject to NDT.
Not so many things to adjust and is relative easy to control your weld and heat input :)

I do not see the same amount of defects when a weld is done with GTAW as I see with other methods.

If your opinion is that a new fresh welder will learn to pass RT/UT with GMAW quicker than GTAW....you are free to have it, I just don't agree.

When I certify welders, may it be a first timer or a re-certification I also see a greater pass rate with GTAW.

When I helped in our NDT department, I saw a greater pass rate with GTAW, than with GMAW or SMAW

3.2
Parent - - By ssbn727 (*****) Date 08-03-2009 17:15 Edited 08-03-2009 17:23
Certifying and training are two different circumstances therefore, leading to different results... Improperly trained, and welders with not enough experience in the specific process will always result in these groups of welders having a tougher time attempting to become certified regardless of the process being used at the time of certification...

Btw 3.2, do you perform any training of welding personnel, and/or have you done any in the past? If you did and currently train as well as certify welders, you would understand what I just explained. Your debate - argument or whatever noe wants to describe it as - is futile and immature at best, so give it up 3.2!!! Your argument doesn't have any validity at all with respect to training, and/or learning the GTAW process in comparison to GMAW, FCAW or SMAW... I rest my case.
Parent - - By 3.2 Inspector (***) Date 08-03-2009 17:21
I don't train welders myself.
Maybe thats why I did not understand how your post makes sense in regards to the discussion.

3.2
Parent - By ssbn727 (*****) Date 08-03-2009 17:28 Edited 08-03-2009 17:31
You finally admit the main reason as to why you not only understand what the meaning of this entire discussion/argument is focusing on!!!
There is hope for you after all - no matter how little it seems!!! Remember to always keep an open mind 3.2 and you will see many more doors open up for you - Young "Comme Mierda!!!" :) :) :)

Henry
Parent - - By 3.2 Inspector (***) Date 08-03-2009 17:42
Show me where I am immature and I will refrain from calling you an old stubborn man.
I will tell you again, I CERTIFY and RE-CERTIFY welders, and I see a greater success with GTAW compared to any of the other methods.

I inspect welds on power plants and oil installations, and I see a greater succes with GTAW compared to any of the other methods.

I have helped doing RT, and I see a greater succes with GTAW compared to any of the other methods.

I do vendor inspections worldwide, and I see a greater succes with GTAW compared to any of the other methods.

I have been in the welding industry for about 20 years, and I see a greater succes with GTAW compared to any of the other methods.

Do you start to see MY opinion on this subject?

Not sure why it is so hard to understand that IN MY OPINION GTAW IS MORE EASY WHEN IT COMES TO WELDING PIPES SUBJECT TO NDT.

3.2
Up Topic Welding Industry / Inspection & Qualification / SMAW instead of GTAW for root pass for Process Piping
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