Question Concerning RMD vs Short Arc Welding

By TimGary (****)

Date 07-28-2013 19:09

One of the main pushes behind RMD, or STT, is to offer an acceptable alternative to GTAW for pipe root welds.
...Cheaper and easier than to GTAW all the way out, or split processes.

Tim

By ZCat

Date 07-29-2013 18:37

Another thing they claim is that with RMD you can weld stainless pipe without a back purge and get acceptable results. I haven't tried that yet, but that RMD arc sure is a lot smoother than short arc.

By 357max

Date 07-31-2013 02:55

These are not new GMAW processes but a modified short circuit metal transfer mode. These are two different ways of modifying the Short Circuit Metal Transfer by two different manufacturers.

By welderbrent (*****)

Date 07-31-2013 04:01

Besides the length of time GMAW has been around, better than 40 years, I believe these machines for STT and RMD have been out at least two to three years haven't they.

Anyway, it is very interesting some of the things we can do with the processes due to advancements in technology. At the same time, GMAW will always be GMAW. And short arc still isn't acceptable as a pre-qualified process for structural, no matter how much 'better' it may run.

Have a Great Day, Brent

By ZCat

Date 07-31-2013 10:08

Who said anything about structural? I asked about pipe welding.

By welderbrent (*****)

Date 07-31-2013 14:21

I know you did ZCat. It was just an observation based upon the actual welding parameters of the process.

I am with some of the other comments you can find if you use the 'Search' function here on the forum. One of these works better than the other but the bottom line is that it will always be a matter of personal preference and dollars; and even personality preferences for a particular salesperson. And when you compare the old with the two newer ones, sure, they are really sweet. But, I still run three older GMAW machines for my shop's applications...Dollars, need, application. And, sometimes all the technology just makes it more difficult to tweek the machine unless you happen to be a computer genius...and that's sure isn't me. (Not saying that that is the case with these machines, but it sure is with some, especially the GTAW's)

Anyway, I was't confusing the issue, or at least not trying to, just commenting about what the process actually is. And, GMAW-S is still GMAW-S. Personally, I don't really care for them on pipe either. Sure, good looking welds can be put in. They will even pass an RT. But they aren't strong enough for me. Seen to many GMAW-S welds pull apart that looked pretty good. NO PENETRATION.

Have a Great Day, Brent

By ssbn727 (*****)

Date 07-31-2013 18:46

Unless someone is knowledgeable, and experienced enough with the equipment, they will indeed have a learning curve in order to successfully set the parameters as well as mastering the techniques required to repeatedly deposit strong, tough, sound, and ductile root passes with excellent sidewall fusion and penetration that will consistently pass all of the required destructive tests... Demonstrations and pre-installation training should be a prerequisite IMHO... :roll:

I agree that the investment that one needs to lay out for purchasing that sort of GMAW equipment is one of the primary reasons why some folks hesitate on trying them out via outright purchase without including proper training by an already skilled technician that's already mastered the nuances one must develop in order to be considered eligible to educate the end user, and can get them up and running sometimes in one or two visits to the shop floor... Finding enough technicians that realistically can do such task will not be an easy one, and the added expenses required from either the supplier or the customer will also be difficult to accept unless this type of GMAW equipment can be demonstrated and proven to recoup the initial investment costs of training, installation and assimilating into the manufacturing of product with sustained improvements in both decreasing the time to produce as well as increasing repeatable quality in a relatively short time frame... So that's what makes the potential customer more than likely to balk at this application...

And even before considering approaching a potential customer, the supplier/seller has to make sure that the equipment will indeed improve the potential customer's bottom line by studying their manufacturing processes and focusing on how applicable the equipment will be for their production of X, Y and Z components... The supplier must also convince the potential customer that the equipment will not only be used for depositing root passes and this is where dual scheduling with another wire feeder will become advantageous so long as the correct power source that's capable of dual scheduling is being used to supply the welding current... In other words, on the production line, this equipment will not be accumulating dust @ it's location... The end result to be achieved is to dramatically increase production as well as improving the overall quality mainly by practically eliminating weld repairs... In summary, only some potential customers will be able to take advantage of this equipment and variant of GMAW S and the the supplier and customer must insure through researching that the system is applicable to increasing the bottom line as well as retaining a loyal and happy customer. :lol:

Not a simple task at all IMHO.

Respectfully to most,
Henry

By aevald

Date 07-31-2013 20:12

Hello ZCat, I have followed some of this thread for a while now and it also parallels some information from past threads with slight variations in how the questions were asked.

I believe that you will find that RMD, PipePro, STT, and any other systems that are offered for modified/advanced arc control of solid wire applications will, in fact, aid with a shop's bottom line. I believe that some past questions were directed at how to qualify PQR's and provide documentation of these processes since the manufacturers will not issue propietary information that is generally required on these documents regarding parameters.

I don't know that that has really been addressed or answered as of yet. I believe that Henry made a statement in this thread that really is at the root of the value of these systems for shops. They have to be understood and utilized for their intended purposes and put to use often or continually. If you are going to invest in one of these systems you need to have a good support system from the local LWS or a district manufacturers rep., they have to be willing to spend whatever time and effort is required for you to fully utilize and understand the technology encompassed in these systems. That is likely the "thing" that will make or break successful implementation of this technology.

You may be well aware of much of what I have to comment on in this paragraph, yet others might not be so privy so I'll give it just a brief run-down: old-school conventional short-circuit transfer has generally encompassed use of gas(es) that are 80% or less of Argon and voltages that are below the transitional level of globular transfer (left this open as there are variables that make this voltage value vary a bit). As there are no external puddle formers you are strictly relying on surface tension to support the bead and provide for it's management. So in essence there is little wiggle room for bead/puddle control or the ability to carry great amounts of weld metal. With the advent of many of the advanced process welding power sources and their mated feeding systems there have been many changes and improvements for weld metal control. Inverters are the major part of this, items such as current,voltage,hertz control, and controlled wire feed have provided for welding abilities that conventional systems cannot match. Power sources now can sense the point where the surface tension of the puddle has almost been breeched and pull back on the wire being fed into the puddle to prevent loss of control and also reduce spatter by limiting the "explosion" generated when conventional short circuiting takes place. There is associated circuitry provided on these machines that literally takes a "sampling" of the current welding parameters hundreds of times a second as the welding is taking place in order to adjust the machine's electrical output and modify wire speed/feed.

I will be the first to admit that I certainly don't understand all of the technical aspects of these systems, yet I have witnessed and used some of them and they will simplify many challenges that we couldn't address in the past. Just my $.02 for what it's worth. Good luck on your queries and best regards, Allan

P.S. I always like following threads like these as there is so much to learn and experience as new things come around the bend

By TimGary (****)

Date 08-01-2013 12:48 Edited 08-01-2013 14:56

Great info, as always Allan!

Just to add a few more cents worth for those who are interested...

My shop specializes in GMAW of carbon steel, structural and sheet.
We have in the past done all of our sheet GMAW with Short Circuiting.
The pros of which, as most know, are the ability to make small welds, in all positions, reduced potential for burn through, reduced distortion, and gap filling abilities. Also, there's the fact that most any GMAW system can Short Circuit, even the cheapest ones.
The cons are that it produces lots of spatter, it's slower than molasses on Christmas, and it provides low joint strength in structural situations.
Spatter is a big money waster for us because we pay too dearly for filler metal to see any of it go to waste, and our quality requirements demand that we have to pay someone to clean it all off our product.
To combat this, we have rebelled against Ed Craig's advice and converted to Pulse technology. There is a definite expense involved in doing so, especially since we're talking of hundreds of welding stations in three facilities, but the return on that investment is pretty short once you consider that, in comparison with Short Circuit, with Pulse we can:

Increase deposition rates threefold
Make welds with little to no spatter
Reduce cold roll, extreme toe angle, lack of fusion and under cutting defects
Use low range pulse for sheet, and high range for structural

We chose to invest in Miller Axcess GMAW systems as that choice allows us to fine tune consistent arcs in a variety of transfer modes and variations of Pulse waveforms.
With this system I can Pulse anything from a 3mm gap in 16 gage sheet up to full penetration structural joints in inches thick steel, however, we still choose to use Spray transfer for our heaviest materials.

The main point of this too long post is that while Pulse is great, it's not good for our 18 gage sheet, especially when a gap is involved. Don't get me wrong, we can weld these with pulse, but it has to be turned down so low that it makes spatter while burn through and distortion rates climb as well.
In this case, we've found that RMD is a great alternative.
With RMD, you get all the benefits of Short Circuit, plus the advantages of being able to fine tune arc lengths and widths like pulse, along with little to no spatter and minimal distortion / blow through.
The only things that I don't like about RMD are that it does not provide the joint strength or deposition rates of Pulse, and it costs so damn much.
Correct me if I'm wrong, but the way I understand it is that Miller's RMD and Lincoln's STT are basically the same thing, and that neither of them invented it. The Inventors, who still hold the patent rights, allow manufacturers to install the program in their equipment, but make a royalty on each machine that uses it. Miller has the software already programmed into their machines, but after an 8 hour trial period you have to pay an extra $1,500, per machine, to permanently unlock it. Lincoln is now providing STT in a separately purchased module.
For these $ reasons, we only use RMD in a few stations that need it.

I've never tried to RMD on pipe, but I can see the advantage of being able to make user friendly, acceptable root pass, and fill/cap with the same machine and operator.

Tim

By Lawrence (*****)

Date 08-06-2013 17:06

Rebelling against Ed Craig!

Love it.

Ed may have to change his tune about thick section GMAWP when the new OSHA standards on fume (moybdinum) come into force.

Cant build skyscrapers with TipTig :)

By welderbrent (*****)

Date 07-31-2013 22:06

I guess there is one question to your OP that I don't think any of us has actually answered plainly.

It is afterall still short arc. You just have to make sure you are using it within the essential variables of your WPS and you are good to go. There are other variables that won't be effected because they are not essential variables.

You did not fill in any of those blanks for us so we can't answer much closer than that.

Great additional info Henry and Allan. You guys are great resources and probably have more experience and knowledge of these units. As I stated, other than 'playing' with them, I have not tried to use them in my shop as it did not appear to be cost effective to make the change in equipment. And I don't really have the need for a change with my applications for GMAW-S. Henry said it well, those are key items. Unless you have money to burn and just want the newest, latest, greatest to show off.

Have a Great Day, Brent

By ZCat

Date 08-01-2013 11:41

I'm welding in a big pipe fab shop, they bought a couple of new Miller Pipeworx 400 machines that have the RMD. I wanted to try it out and it worked really well. It's pretty much the same as short arc, it's just smoother. We do a lot of short arc roots and DualShield fill and caps. It might not be great for structural, but it works pretty well for putting roots in pipe.

By welderbrent (*****)

Date 08-01-2013 14:20 Edited 08-01-2013 14:27

Z,

I know you have been around a bit, but, I don't really know much about you. This thread has been more info than I would have known before now. Thus, I don't know how much about WPS's you know/understand.

As I stated in my last post, if you are operating in the same basic parameters then your existing WPS should be able to cover you. Gas shield (Ar/CO2 75/25 or 80/20), low voltage (16-22ish, though usually more like 16-18), applicable wire feed speed (don't have any numbers jumping out at me at the moment), about 1/2 - 3/4" stickout, You should be in the ballpark. Sound about what you were running? Most everything else is non-essential.

I agree, short arc can work well for pipe roots. My main objection is not as much with the process as it is with the operators and lack of training and the ability on most machines for them to adjust them when you aren't looking. You should see some of the setting my guys have said works better for them. SO WHAT?!! It isn't correct and it isn't penetrating set there.

Now, as to Henry's comment when I mentioned that before, yes, I agree. And, I personally have a PQR and have qualified on short arc to D1.1 on 3/8 plate so am good to go to 3/4 (according to the papers). I almost never use short arc beyond 1/2 if even that. That's what I keep spray arc, dual shield, and SMAW around for. The right process for the job with the highest chance for success. No need to gamble with people's lives. Most of my work remains on the top side of grass and is on the highways or around people with various safety functions and/or factors. I don't like to take needless chances. Just because I can do it doesn't mean anyone can.

Anyway, hope the wps question was answered. Sorry about the distraction from your actual question with all the other comments about the process though I do appreciate all the new information I now have.

Have a Great Day, Brent

By MMyers

Date 08-01-2013 16:11

Thinking out loud here. I'm not a code guy by a long shot, but something tells me running GMAW-SST/RMD/whatever process and using a GMAW-S WPS would not fly because it's a change in process. Thoughts?

And if I haven't ever mentioned it before, I highly advocate limiting what the code allows on WPSs if the responsible party feels its necessary. I'm of the opinion that just because the code says you can doesn't mean that you should. Again, not a code guy, I'm pretty sure somewhere in there it mentions that it's a set of "minimum requirements", which means that it can, and probably should, be tightened where necessary.

By welderbrent (*****)

Date 08-01-2013 16:30

Those are not processes. They are different models of machines with different technology operating within the same parameters of the old machines. It is still GMAW-S, at least as long as you run it in the gas, voltage, amperage range of short arc. If you crank it up and change the gas then it is GMAW (spray).

Tweeking the things that the technology allows you to tweek in order to fine tune the frequency and other factors of the arc does not change the process.

It's similar to calling GTAW by the mode name of HELI-ARC. It is still GTAW, just different because someone called their machine and set up with Helium gas by that name and it stuck.

Now, we have sweeter running GMAW short arc machines that are called by the name of the model unit that either Lincoln (SST) or Miller (RMD) makes. That doesn't change the defined process.

Lastly, I whole heartedly agree with your 'minimum' standards application. I even encourage welders that way with pre-heat and many other parts of the code, it is a minimum. Going beyond, within reason, is a good thing. The Seismic codes and Bridge codes do tighten up the D1.1 which is the main basis for my stand and what I call 'within reason'. Obviously, you can go too far in some cases.

Have a Great Day, Brent

By MMyers

Date 08-01-2013 16:46

I respectfully disagree. GMAW-STT/RMD use pulsed technology to deliver a high current pulse to break the short circuit. This is different than running a CV machine down low enough to achieve short circuit.
Ref: http://www.lincolnelectric.com/assets/US/EN/literature/NX220.pdf
Miller literature is quite a bit more vague about it, but there is a schematic outline of the pulsed waveform and transfer modes: http://www.millerwelds.com/resources/articles/RMD-Process-is-Easy-to-Learn
http://www.millerwelds.com/about/news_releases/2004_archive/images/Fig.1RMDBallTransfer.jpg
This is different than a trade name change (GTAW vs. Heli-arc), it is a completely different technology and method of making the weld/transferring metal all together.

By welderbrent (*****)

Date 08-01-2013 17:44

Well, if that is the case then I agree with you Mike. I had not been introduced to them in that fashion.

Not only would you need a different WPS, you would probably need a PQR as the pulsed system is not going to be... there I go thinking D1.1 again. He is welding pipe so he will have to get his procedure qualified anyway. Bottom line is that the pulsing rate will be an essential variable that will have to be monitored and set within the same parameters each time. Can't be adjusted outside certain limitations in order to accomodate different gaps, thicknesses of pipe, etc. And how do you check that from the inspectors point of view? Is there a meter that will give us a readout on pulsing cycles so we know the machines digital readouts are accurate?

But, if they were basically set so the pulsing was non existent or within the same tolerances as short arc, then the wps would still work wouldn't it? Just because it has pulsing, doesn't mean it is in use at all times.... at least not outside acceptable limitations?

Looks like we need someone with much more knowledge of the machines than I have to give a good answer with that information added.

Tim is using them in mass. Maybe he will chime back in here with some useful information.

But, Mike, I still don't think it is correct to say it is a different process...But, as spray, globular, and short arc are different applications of GMAW, so is Pulsed. As has been described before, like pulling the trigger, letting go, pulling...weld, stop, weld, stop... but when it is a part of the regular setup it has to be monitored as well as tested to make sure you will get the expected final product.

One of those terminology differences.

Have a Great Day, Brent

By welderbrent (*****)

Date 08-01-2013 18:09

Reading back through Tim's earlier post here, it appears those are standard GMAW machines with special programming abilities but you can use them without the pulse. Even if you have paid for the expensive programming.

So, I would still maintain that it would be 'POSSIBLE' to use the same WPS, but you would have to, as said before, still operate totally within it's stated essential variables.

Now, is pulsing an essential variable? Sure, if you set it so the weld pool cools way down it may not be desirable, but that in itself does not make it a variable. I don't have an API 1104 or ASME here for any piping applications, but I don't know how that would play in.

I don't see in D1.1 Clause 3.6 where the pulsing would effect the WPS. I don't have my B2.1 or Guide for WPS's here. I know there is a block on the WPS for 'Pulse' but at what rate is it just short arc? It does not asking what settings compared to travel speed for example. Obviously, just as travel speed effects any welding, it will with pulse as well. But how about the pulse cycle? I don't see any concern for that within the codes.

Not trying to disagree with you Mike. Trying to make sense of this for myself as well as ZCat. Hopefully I'm not just confusing him.

Have a Great Day, Brent

By MMyers

Date 08-01-2013 19:08

No offense taken at all, I like good discussion. I really like discussions that involve power supplies. One could describe me as a welding power supply gear head (though I mainly work with GTAW machines)

I tend to take the uber conservative road and would exceed code specified minimums and hold that the pulse program/waveform/machine is an essential variable and would write the procedure as such. Overkill? Maybe. Safe? Absolutely, and that's where I'd rather be at the end of the day. A procedure qual and restrictive WPS are far less costly than an accident. That's what I was trying to communicate by saying it's a different process, though that may not be the verbiage the code uses.

I suspect that this might be an instance where the technology has outpaced the code, though I don't sit on a code committee so I'm not sure if that's actually true. If I remember my welding power supply history correctly, old pulse GMAW machines just had a pulse frequency dial on them (old Linde machines maybe...?) - I think that's where the frequency field you're seeing in the code comes from. Today, and I've done it, you can hook a laptop to a machine and adjust all of the segments of the waveform. Now, I don't think that happens often, but there are applications where it's worth it for the engineer/technician to experiment with this during the development phase of getting a weld qualified.

From an audit perspective, I think there's two ways to handle it, both are equally annoying. The first way is pretty direct: you could open the program in its editing software and verify the pulse parameters haven't changed. That will get you 99% of the way there for 99% of the customers. The other way, you'd need a current probe and an oscilloscope - those two tools will let you see current. So one approach could be to provide a "screen shot" of the waveform during the PQR, and compare it to the waveform during use. The problem will be that the waveform will not look identical at each welding machine setting, so one would need to specify an audit procedure (i.e., the PQR procedure). The one concern I have with this method is that the switching current of the output section (inverter welding power supplies are overweight switch mode power supplies (that's the generic name if you want to read about them), so the power delivered is not constant, but switched above audible range - this is not the same as the pulsing we're discussing) might obscure the welding pulse current. I'd have to hook up my toys to see if this is the case. I know on my GTAW power supplies voltage is a super noisy signal when viewed on a scope because of the inverter output.

By TimGary (****)

Date 08-01-2013 19:44

Hey Mike,

Sounds like we're pretty much in the same page as far as procedure overkill is concerned, but I think you might be over doing it on the auditing though.
Maybe its just my situtation that allows a simpler technique...
We have welding stations set up to put the same welds on the same product day after day.
I just set the operator up with the ideal transfer mode / wave form for that station and lock the machine so that it cannot be adjusted outside of the WPS range.
This makes auditing simple.

Tim

By MMyers

Date 08-01-2013 21:27

Absolutely overkill on the auditing. I was going after "purity of the art". But looking at practicalities, I don't see any other way one could verify that the weld being made today uses the same waveform that was used on the PQR - I think welder WPS compliance could probably be adequately handled using standard practices. I think this is one of those times where it'd be wise for the customer, engineering, and quality need to hammer out the requirements ahead of time.

I think one of the larger issues is when power supplies are changed from model to model or brand to brand. I could see that getting ugly (costly).

By aevald

Date 08-01-2013 19:48

Hello Mike, as I mentioned in an earlier post, I do believe that this topic has come up before in a slightly different context but definitely with a similar result. With everything that is going on electrically and mechanically within these high-end systems I believe that it really does tax the methods/means of meeting WPS and WPQR requirements as they relate to code requirements/needs regardless of application. I would hate to think that you would have to provide oscilliscope/voltage/current "snapshots" to provide proof of compliance and adherence of range requirements. Don't know of any other answers either though, I'm sure that the committees that have been faced with these questions have similar thoughts in this regard.

I am often in awe of how welding has progressed with regard to systems, processes, and applications. Even in the relatively short years of exposure and actual availability of "welding" abilities of mankind's history we have come a long ways. There has certainly been an exponential growth of the technology as well. I believe that it may have been you that mentioned the code bodies possibly not keeping up with the technology of today, I believe that is true to a great extent, often times much easier to develop the technology and to put it to use than to verify it's fit and function in a manner that is easily recognizeable,verifiable, and trackable.

Enjoying this thread immensely everyone. Best regards, Allan

By TimGary (****)

Date 08-01-2013 19:28

The thing I both like and dislike about AWS codes is that they leave so much gray area open for interpretation.
Generally, I cover these areas with the CYA method and choose the most stringent interpretation.
D1.1 and B2.1 generalize "Processes" as SMAW, SAW, GMAW, FCAW, ESW, EGW and GTAW, EBW, LBW, OFW, PAW and SW.
They go further to recognize the difference in GMAW transfer modes in that D1.1 PQR essential variables lists only "A change in the mode of transfer" for GMAW, and B2.1 essential variables for FCAW and GMAW state " A change in the mode of metal transfer from short circuiting to globular, spray, or pulsed and vice versa."
Other than that, you have to follow essential variable % changes in amps, volts, WFS, etc..
ASME and API essential variables are even less stringent.
A loose way of interpreting this would be to say that variations of pulse are still pulse and variations of short circuit are still short circuit, as long as the end result stays within the qualified amps/volts range.
However, I have trouble keeping track of the amps/volts ranges in these modern wave forms that have been springing up ever since new high speed switching technology has allowed computer programmers to change arc characteristics 1000 times per second.
Each manufacturer is now in such a race to out complex the others that new welding machines are just big computers on steroids and you have to have a degree in "Welding Scientology" just to understand all of the available options. In some cases you have to use a separate computer just to set the damn things.
Do I sound like an old Curmudgeon yet, because I feel like one?
Don't try to take my new machines away and swap them for an old rectifier though... Once you figure them out, they can really weld, as long as you don't exceed the duty cycle. I'm dreading the day my new welder catches a virus...

Anyway, back on track.
As standard CYA procedure, every time I put even a slightly different wave form to use, I qualify new procedures and write detailed WPS to go with it.
I guess that's why my procedures book is now 4" thick...

Tim

By welderbrent (*****)

Date 08-01-2013 21:41 Edited 08-01-2013 21:44

Great additions guys, thank you from this inspector that hasn't had the 'pleasure' of running into this issue as of yet.

Now, OUCH. That could really put a small company in a bind depending upon the code being applied. How about in ZCat's case? It sounds as though he is going to need a new wps with all the supporting PQR's to go with it. Even if he took a lower road, which may be within reason though definitely lower than Mike's, it could still take a fair amount of work, time, and money.

I'm glad you guys were watching this. My simple understanding could have misled him, and I had even gone back and glanced through some of the other threads to make sure my memory was serving me right about what SST and RMD were. Still didn't fully see the difference with the pulsed arc.

Have a Great Day, Brent

By aevald

Date 08-01-2013 22:17

Hello Tim, all great stuff that you are contributing here and certainly providing "food for thoughts". In our school shop we have the 352 Invision and matched feeder, a number of 350 MPa's and matched S74MPa feeders(8 systems), and a couple of Thermal Arc SP320's, all of these qualify as versions of advanced process power and feeding sources. WAY to much stuff to learn about in short order with all of their in's and out's. Haven't even looked at some of the options for use of SD cards to store welding parameters or modification of internal waveforms, or hook-up to the internet to provide for factory assessment and trouble shooting of systems if required or desired or an ethernet to provide for local tweeking.

One of the larger mechanical shops in our town is equipped with a "bunch"(I'm guessing 15 to 20+) of the PipeWorx, RMD technology and do a lot of roll-out work and in position stuff on various kinds of piping of all types and materials. They do the applications justice for what they are fabricating I am sure. Even the limited scope of this thread(when you consider welding as a whole), just goes to show that there aren't just a bunch of "dumb" welders out there everywhere anymore. Best regards, Allan

By ssbn727 (*****)

Date 08-02-2013 02:16

:

http://www.aws.org/cgi-bin/mwf/topic_show.pl?pid=34931;hl=WPS%20for%20Pulse%20GMAW

This one goes back even further (2003):

http://www.aws.org/cgi-bin/mwf/topic_show.pl?pid=20532;hl=WPS%20for%20Pulse%20GMAW

Well, that's all I could find that had any sort of relevance to this thread... Let's see if the pirates are winning! :eek:

See ya later!

Respectfully,
Henry

By welderbrent (*****)

Date 08-02-2013 03:50

Leave it to Henry to supply us with our next year's worth of reading. I have gotten through the first three and there truly is much in there about the current question. A couple of good posts thus far from Al, who probably hasn't been heard from because he has said it all before... LOL.

Z, are you getting this?

Thanks Henry, who won?

Have a Great Day, Brent

By ZCat

Date 08-02-2013 09:50

Yeah, I'm getting it...I think. :eek:

Looks like a giant can of worms. Truthfully, I don't think these guys I'm working for even know the capabilities of their two new Pipeworx machines. I doubt they are gonna be interested in putting out the cash for a new procedure when they only have two of these machines. Too bad, though, that RMD sure is smooth.

Thanks for all the replies, everybody.

By welderbrent (*****)

Date 08-02-2013 14:02 Edited 08-02-2013 20:18

I understand. And if you look at... I think it was the second link that Henry just put up, there were some comments from Al on just how complicated it truly can be with all the different operating variables of those machines.

Now, my question then still is rather much of that is an essential variable within the scope of your particular application. You may find it isn't that difficult but that it is necessary.

Almost sounds like a case of wanting the latest technology, getting talked into by a salesman, and then finding out it is not as practical and even applicable as promoted to be but will definitely cost a lot more time and money before it is finally ready to roll.

At least you can now procede with your eyes wide open.

Have a Great Day, Brent

By JTMcC

Date 08-02-2013 19:16

RMD and SST are kinda new, but not brand new.
The people I know that are using one or the other in a shop pipe fab environment are just tickled pink with the results.

Just like any other new(er) tech, the end user doesn't have to understand every nuance embedded in the computer chip. He only needs to know what relates to the work in front of him at the time and that can be very manageable. Learn the parameters on your range of work and away ya go.

The numbers on big bore pipe shop fab with both of those systems is VERY impressive from a throughput standpoint. And that's where a lot of money is made, people are gainfully employed and companies thrive. Those people who've learned to max that tech in their little scope of work are just killin' it. Almost unbelievable production on pipe root pass times.
Most I know are doing fill/cap with either a (gas shielded or not) flux core wire and they really turn out large volumns of pipe work. The productivity is almost stupid for the one's willing to learn what's needed for their applications.

If we worked inside I'd be all over either process. They are a deal changer on inside pipe fab.

J

By js55

Date 08-02-2013 20:16

STT has been around I know for almost 20 years. We ran some of the first production machines, that I know of, in the mid 90's.
And you need to take a look at ASME Section IX as peratins to qualification. The controlled wave form machine qualifications are undergoing rapid changes.
ASME has a working group devoted just to them. One of our disitnguished contributors is chairman.

By ssbn727 (*****)

Date 08-03-2013 11:46

I couldn't see it being used in structural shops unless they have mostly open root joints up the gazoo... Maybe some larger sheet metal manufacturers...
Automotive manufacturers have also been using this GMAW-S variant mostly in both Europe and Asia first, then the big 3 for quite some time now...

I agree that for pipe shops, one would be foolish not invest in one of these systems so they're a no brainer but, not everybody out there is a pipe shop even though some shipyards could definitely benefit from these in applying them to deposit welds as the root passes in many of the open root joints that can require a whole lot of filler, time and effort to do so otherwise from a production standpoint...

In other words, there are several industries that can definitely take advantage of this variant of GMAW-S... However, not all industries can really justify their purchase because they would more than likely spend most of the time collecting dust because of the limited applications due to not enough use for their type of production welding IMHO. :roll:

Respectfully,
Henry

By Lawrence (*****)

Date 08-03-2013 13:37

My opinion,

STT/RMD or cold metal transfer

If the electrode wire touches the base metal regularly it is "short circuiting" by definition.

The length of the arc is controlled by arc voltage therefore the process is CV as far as D1.1 is concerned.

If the RMD/STT can be deposited within the WFS and voltage ranges supplied via your current PQR's, in my opinion you may proceed with production after any WPS revisions occur (within PQ ranges of course)

I think this is what the OP wanted in the first place

By JTMcC

Date 08-03-2013 14:55

No not everybody out there is a pipe shop, but the original post was about pipe root welds. Then it got steered, like a lot of threads do, off into structural steel land.
But he specifically ask a question about open butt pipe welds.

J

By ssbn727 (*****)

Date 08-04-2013 05:45

I mentioned "pipe" shops also. :roll:

Henry

By ssbn727 (*****)

Date 08-10-2013 09:56 Edited 08-10-2013 10:26

Hey Brent,

I apologize for missing your post asking me who won the baseball game... The Pittsburgh Pirates did! :cool:

I cannot help myself when I post up some reference material that ends up becoming a project to read because sometimes I forget that most folks in here really don't always have the time to go over the "stuff" I post in detail and that sometimes complicates the thread inadvertently... My bad! :eek:

Lawrence is so right with what he wrote regarding the comparison of these brand name distinctive variants of short circuit arc transfer as well as the Fronius welding equipment being the best performing of all the different power sources! I couldn't agree more with his opinion regarding Fronius as being "the best equipment on the planet!" :cool:

When I was @ Maglev/ONRL, they had Fronius welding power sources interfaced with IGM robots from Austria and that system was truly impressive in how seamless the execution of the programming was when put into action! The prototypes for the base structures/Guideways that were made so the Maglev cars would hover over as they traveled over them were being assembled, and welded together with the Fronius/IGM systems...

These had to be built to very tight tolerances for the type of precision required so that the cars would not encounter any sort of warpage/distortion that could easily be the cause for the cars to make contact with the structures, and potentially damaging the super conducting magnets which were placed @ locations underneath the car, as well as wrapped around these base structure/Guideways in such a manner that led to very little separation between these magnets and the Guideways...

There was also the possibility of the cars basically "Derailing" off the Guideways even though there was no actual physical contact with the cars running over them when they traveled over them, especially if the magnets were dislodged on the sides of the bottom of the cars and no longer maintaining the distances of separation from making contact with the guideways... This would become a catastrophic event!

Since each of these prototype Guideways were on average over 50' in length and shaped like a Capital letter "T" with the vertical line of the letter shaped like a capital letter "V" and, the top horizontal line of the Guideway extending out with each end having shorter vertical lines shaped like rectangular tubes attached to them terminating almost 2' from each end of the "T" shaped part of the Guideways so that the Maglev car bottoms containing the superconducting magnets wrapping around the top, side & bottom of horizontal & shorter vertical lines of these structures could maintain consistent distances of separation between each...

Such precision, accuracy and repeatability was required because many of these components had to be fabricated in order to use as the guideways for which the Maglev cars would hover over without making actual contact with them at all! And the distance of separation between the superconducting magnets, and the guideways had to be consistently accurate with very little deviations within the tolerances required in the distances between them... The precision, and accuracy that was demanded for these structures, and the welding equipment interfaced with the right robotic system was a must for such repeatability!!! And with Fronius, and IGM performing the best in the competition out of many different welding equipment, and robotic systems available during their evaluations between each of them, and I got to witness most of the demonstration trials for these systems!!! :lol:

So like Lawrence, I got to personally witness how well the Fronius equipment performed against all of the domestic welding equipment manufacturers as well as most, if not all of the foreign equipment manufacturers, and I have to say that the repeatability to deposit as close to perfect 100% RT & UT quality welds were truly impressive especially being able to repeat such quality on so many large groove and fillet weld joints and in different positions regardless of being mounted on independent positioners also! :cool:

I don't doubt for one minute how well Fronius CMT advanced process equipment would be able to produce excellent, repeatable quality welds on pipe regardless of the material! :cool:

Respectfully,
Henry

By welderbrent (*****)

Date 08-10-2013 13:44

Henry,

Thank you for that update. Shows you read and are interested in even the little things we post up. I don't have tv in any form. If I want to watch something we get a movie or watch one from our collection, which got greatly diminished when my wife sold all our VHS's, lost some great oldies there. Thus I don't get sports though I have never been BIG on sports anyway. I listen to the morning scores while travelling to jobs but most of them don't stick. But, I use some for conversation such as your post on the pirates.

Also, I do appreciate your posts with references. I read some to see how they relate to the thread and save others for later. I admit, I don't always get to all of them. But they are great material and the ones that really hit home I save to my documents and put in folders where I can find them under specific headings.

Thank you here for the info on Frontius. We are moving the shop and I am going to get a new welder for doing certifications and the small jobs we will keep besides doing the inspections.

Have a Great Day, Brent