Hi guys,
A couple of posts from a while ago on my opinion of Lincoln STT welding
Hi all,
First used Lincoln STT in New Zealand in the late '90s for light, medium and heavy wall carbon and chromolly piping.
Absolutely brilliant machine when set up properly.
Root with STT and Fill & Cap with SAW using pipe rotators.
The great thing about the STT (apart from the speed) is that a uniform fit-up is not required. If it is GTAW you need a consistent root gap all the way around the pipe but STT is different.
The gap could be 0 - 4 mm (we considered 4 mm to be maximum gap) and we would have 3 large tacks (bridge or root tacks, it didn't matter).
Weld between 2 & 3 o'clock from one tack and stop just short of the next (unless it is a feathered root tack)
Take a 7" or 9" grinder with a cutting disc (we called them pipeliners, about 3.2 mm thick) and cut through the prep in places where the root gap is less than 3.2 mm.
The beauty of the STT is there is no need to remove the "swarf" that has been pushed into the pipe by the cutting disc. The weld burns away the swarf and you end up with a GTAW like root run at about 5 x the speed.
Have also used for vertical down on 6 mm square butt groove welds for thin walled tanks.
Regards,
Shane
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