STT Process - Pipe Welding

By jon20013 (*****)

Date 06-10-2005 12:52

We have not used that process here although one of our vendor's has and does and I can tell you from observation that the welds produced are beautiful. Do you have a link to the brochures? What about system set-up costs, any idea?

By chall

Date 06-10-2005 13:06

http://www.mylincolnelectric.com/Catalog/equipmentdatasheet.asp?p=448

http://www.mylincolnelectric.com/Catalog/equipmentdatasheet.asp?p=12555

Thes are the best I could find in a short time. The equipment we would be using is Lincoln. I'm sure the cost is "rugged", but if you have the right work in place, and it does what they advertise, it is probably bearable.

The reason we are considering this right now is because our supplier has offered to let us try the equipment for no cost. Since this project is ramping up, it may be worth checking the equipment out.

I'm always sceptical of grand promises. Usually the person making the pitch has an ace who can make the most difficult task look simple. When you try to put it into play, the real world obsticals show up.

If we decide to use the equipment I'll let you konw how it works out.

By Lawrence (*****)

Date 06-10-2005 14:41

Charles,

SST is the cats meow in shop fabrication. The Lincoln powerwave performs as advertized. Surface tension transfer really does work. I've only used this powersource in training and trials but I really like the effect. Even our friend Ed Craig has good things to say about SST. In one of his web articles he has something like an 11 year old kid making code root passes with SST with a half day tranining.

Miller has new technology also. Their answer to SST which has been 8 years in design is called Axcess with RMD. It employs a true hybred of CC/CV in a synergic pulsed short circuit Mig. Its adaptive properties can compensate to uneven root openings in a way nothing else can.. this one really works too. I played with one of these in Dallas and our department is going forward with purchase. Miller says it's technology is a pace beyond Lincolns powerwave. http://millerwelds.com/products/automation/axcess/

If you have time for vendors to demo equipment you might want to have alook at both.

Sidebar
Some codes require CV powersources for GMAW and these Hybreds are actually providing both CC/CV in a single pulse. (http://millerwelds.com/education/tech_articles/articles32.php) If your making PQRs I'm curious how that all will look. Seems like a wierd/gray area. I guess at least with D1.1 there is nothing pre-qualified (3.2.4)

By jon20013 (*****)

Date 06-10-2005 15:23

Thanks guy's! I will check out all of the links provided by both of you although I am (personally) more inclined towards Miller although we have both Miller and Lincoln equipment in our shop.

By Lawrence (*****)

Date 06-10-2005 16:07

Jon,

My shop is also mostly blue. But that Lincoln powerwave is a sweet machine. I really like it's GMAW pulse abilities with aluminum. Their synergic pulsation is awsome. Miller had to develop the Axcess because the technology of Millers XMT just wouldn't compete with the Powerwave.

Another thing I like about powerwave is the design of their wire feeders. I have run 3/64 5356 aluminum right through the standard gun and after one adjustment in tension Never had another birdnest. Those of you who have tried the same with a Miller 60 series will appreciate this.

By jarsanb (***)

Date 06-13-2005 18:58

I have owned the STT powerwave, and to be honest..more bark than bite. Our quality tests show that the same problems occur at the same rate typical to short circuit transfer with the powerwave, but not as easy for the welder to identify. However the RMD by Miller has been fairly impressive. I do prefer standard Lincoln GMAW equipment over Miller but in this case the Axcess wins (to me). We do use GMAW solid wire for all of our pipe welding applications, in the short arc mode. Good parameter setttings with traditional short arc produce consistant X-ray and ultrasonic quality welds. Not sure the additional $10,000 for the advanced short arc is worth it (I do not believe the power source link you listed is correct. The powerwave 455/STT is more expensive,also, wire feeder for this unit is comparable to a standard power source in price). Most places fail on their initial short arc process to begin with and look to these processes for a cure. As far as the Ed Craig x-ray quality 6 year old...it was a about an 8 inch long fillet weld. If he wanted to invest another hour, he probably could have trained a monkey. And god forbid any equipment troubleshooting.

By Shane Feder (****)

Date 06-16-2005 09:32

Greetings to all from "Down under",
Used to work for a piping company in NZ that were very innovative and were forever looking to get an edge over the competition.
In the workshop we were using variable speed rotators that the company designed and built. We were originally "stoving" the root/hot pass runs using cellulose electrodes and then filling and capping with FCAW.
We then purchased 4 Lincoln STT welders (can't remember the models) and we were very impressed with the speed and ease of use on pipework.We put only three tacks in the root and "knifed" the tacks as we welded the root run.The brilliant thing about the process was that the "fit-up" didn't have to be spot on to enable the welder to produce top class welds.The gap could vary between 0 and 4 mm and all you had to do was "knife" the root with a 3 mm cutting disc and the resulting root run looked exactly the same no matter that the root "landing" varied greatly in places. A 12" root run was being welded in approx 1.5 minutes which is a huge improvement on the GTAW process which is usually used for refinery piping.We were then filling and capping with SAW which meant the spools were going out the shop door at a great pace.
The company had the pipe spooling so "cost-effective" that they were exporting spools to Australia and beating local companies prices.
As a CWI and former pipe-welder I can't speak highly enough of the STT process,
Regards,
Shane

By jarsanb (***)

Date 06-17-2005 15:19

With all due respect, you are comparing GMAW-S (STT) to GTAW and SMAW deposition rates. Though I believe you probably compared your results to traditional GMAW-S you have made no mention of it.

By Lawrence (*****)

Date 06-17-2005 15:41

Jar,

Thats a good point. In fairness to regular short circuit mig, it will perform just fine on rotated pipe with an even land and consistant fitup. However, it will not perform as well with non rotated pipe or with uneven fitup. I can also see the senerio that follows with buying a machine to make up for sloppy fitting, eventually the fitting will become so bad that the whistles and bells cannot compensate.

The SST (Lincoln) and the RMD (Miller) are proving themselves in the field. The trick I guess is to listen to the users rather than the sales pitches :)

I'm sure looking forward to our new Axcess work stations and promise to report. Were hoping for some top students to really make up some challenging trials.

By jarsanb (***)

Date 06-17-2005 17:02

I agree with all and am looking into purchasing some Axcess units for semi-auto applications as well. My point is that the RMD/STT is not the best solution for all GMAW applications as pitched by both lincoln and Miller sales reps. For pipe with inconsistant root openings the RMD is excellent(verses traditional short arc) on the root pass. I should mention also that the powerwave 455 is an excellent power source for the other GMAW transfers, just that in my experience with the both the STT and RMD, the RMD operates closer to what the manufacturer promisses.

By jarsanb (***)

Date 06-17-2005 19:27

Lawrence,
I agree with everything you are saying. No exceptions. But someone looking at this post for general info may misinterpret some of the our suggestions. Many less experienced welders feel that GMAW is easy and not as reliable. I work for a public utility and we provide Gas/Electric services to about 19 million paying residential customers in additional to major commercial ones. Our pipelines are welded with conventional short circuit transfer as well as SMAW. The company employeed welders use exclusively GMAW for field applications (construction and repair). For the statement "it will not perform as well with non rotated pipe or uneven fitup.", this statement is true. However, if you read this statement to mean " will not perform WELL" this would be incorrect. Many think that all pipe welding is done with either SMAW, FCAW or GTAW. This company has been using GMAW-S since the late 1960's. GMAW-S consistantly outperforms SMAW in the big picture (time, quality). The welders can use either process in many cases, but, when they fully understand GMAW none ever select SMAW. Some of the more experienced welders have less than one or two repairs a year! Our testing includes all of the NDT processes. RT, UT, ET and on... Each joint requires 3 forms of inspection. 1st -VT, 2nd - RT, UT, or ET, 3rd some form of LT,PT or MT. For transmission lines operating around 1800 psi. they are hydrostatic tested at rating for 6 to 8 hrs. depending on application. I appologize for this dissertation, but find it frustrating that many in the industry do not fully underdstand the operating potential of GMAW, nor the skill required to perform this process as intended. So I am only cautious of degrading the process, discouraging newer welders.