Welding Tips and Tricks

We had MTI Power Services bring in their split frame beveling and cutting machine for a full demo. The project we are working on (seen in "what I welded today" in mig forum) using 30" pipe, we are looking at solutions to extracting a weld if it faile non-destructive testing or if for some reason we needed to cut a pipe apart. While the machine performed flawlessly I would like some opinions from others here. Keeping in mind this machine is to go into a portable welding cell that we are in the middle if engineering and the key is speed, I don't think this is the best option if a 6" section for example fails x-ray, to extract the entire diameter and start over. You can set a depth in you know how deep you need to go but I feel it would be quicker to use a grinder for a smaller repair like that. If you need to extract a longer run than this machine shines. One benefit is it cuts, preps and you are ready to go.
So here is the way I see it for now
Advantages; faster cutting and beveling verses other methods, easier cleanup,

Disadvantages; have to excavate entire parameter even if small section is defective, long set up time even when set to correct diameter, impregnates cutting fluid in weld zone leaving chances for more future defects.
So what do you think? Also if anyone has used these in the field I would like your feedback.
I took two very quick videos that I will get uploaded when I can, until then here are some pics and a link to their video.
https://www.youtube.com/watch?v=yXQd3QEXH5U
-Jonathan

More pics.

I watched the video you linked to and have a question. You said, "Disadvantages; ...impregnates cutting fluid in weld zone". The video looked like they were cutting dry or I did i miss something. What drives the cutting head around the frame?
Looked pretty cool to me but then again, I'm easy to impress.

Here's a thought...

Would it be terribly difficult to make the drive system reverse? Cut 6" of circumference, back up, lower/tension the cutter, repeat for 5 3/4", etc, to the depth required, at the point required? CNC control would be possible with a black/white stripe paint or tape, that could be read by an IR LED. Think a "bullseye" for the imperfect weld on the tape, and the cutter reads the tape, gradually tapering in to the inclusion/LOF/porosity, etc...

With the potential this has, and the engineering already invested, I think the development would be worth the effort. MTI Might partner with you to develop it, for the rights to use it...

Steve S

That's a great idea - but if the cutting action is as it appears using what is essentially a lathe tool being driven round the pipe & a cut increment indexed each revolution ( I assume at the point the rotation slows / pauses unless that's a camera trick ) I doubt it would work as the cut got deeper the distance required to establish the cut depth would be too great - the cutting head would need to be a powered / rotating action more similar to a large tipped milling cutter that could cut directly into the material before moving round the pipe - I have seen a system sort of similar but no idea who makes it - interesting concept - I assume it's primary function is just to create an accurate face cut / edge prep prior to welding rather than removing a defect - though I guess if it was say Tig root with no faults but stick fill / cap & there was a slag inclusion or other fault you could take it back down to below the problem without cutting the entire joint & re- filling.

Ok I will try to answer all questions.
Bob,
Like most demo videos, they show only what they want and always in the best case situations. They don't use coolant in the video to my knowledge but in real life they suggest a water based cutting fluid. Now one argument is you should/might pre-heat before welding again. As for the power, it is air and it is the long black canister off to the right side.

Steve and Brian,
Yes this might be possible however it would need a redesign. As seen it is air lowered and they do offer a hydraulic version as well. It is based off what Brian suggested, it is a cutting tool that advances .004 each time it trips a lever. I did think of the situation Steve suggested going a certain distance and going back but it would have to be alot more advanced than it is. One of their selling points is easy field use with air. There is a machine out there that could clamp around a track and cut into the weld like a chop saw. The draw back is it only cuts straight in and you still have to do the beveling.
I am still torn on this machine. The powers that be think its the best thing since sliced bread and didn't like my opinion when asked about it at all.
-Jonathan

The "powers that be" should not drink the Kool-Aid.

I agree that cutting out an entire weld for a single imperfection is highly impractical.

Sure, that's a nifty tool. But why do 100X the work for a fix because the tool is "nifty"? (and risk another imperfection in the now-massive repair weld?)

Seems to me, a grinder is still the best fix... A li'l old-fashioned work to save a butt-load of time and money over the nifty tool.

Steve S

Otto Nobedder wrote:The "powers that be" should not drink the Kool-Aid.

I agree that cutting out an entire weld for a single imperfection is highly impractical.

Sure, that's a nifty tool. But why do 100X the work for a fix because the tool is "nifty"? (and risk another imperfection in the now-massive repair weld?)

Seems to me, a grinder is still the best fix... A li'l old-fashioned work to save a butt-load of time and money over the nifty tool.

Steve S

What really mad me mad is they are sending them to Brasil to our parent company to get them to buy one or three. Oh well, we keep you posted if or when we get one....or three.
-Jonathan

Hey guys... I know I am new and don't know squat about welding yet but I like looking at this stuff and I am an educated person so I am going to chime in. This apparatus/machine seems to be something that would be GREAT in an area where "Pipeline" was exposed but underground or some place where you have to excavate would be a REAL pain. As for the water cutting, how would that cause a problem? Most likely it will evaporate with the cutting action and or dissipate shortly thereafter and if not just pre-heat the metal.

I think Steve said it best, use a grinder and save some money unless your working on a Oil Pipeline that is suspended above ground.

Just my .02, please remember I am new...

CC
HW!

crazycarl wrote:Hey guys... I know I am new and don't know squat about welding yet but I like looking at this stuff and I am an educated person so I am going to chime in. This apparatus/machine seems to be something that would be GREAT in an area where "Pipeline" was exposed but underground or some place where you have to excavate would be a REAL pain. As for the water cutting, how would that cause a problem? Most likely it will evaporate with the cutting action and or dissipate shortly thereafter and if not just pre-heat the metal.

I think Steve said it best, use a grinder and save some money unless your working on a Oil Pipeline that is suspended above ground.

Just my .02, please remember I am new...

CC
HW!

CC,
I agree that this machine does have its good applications. They have hundreds of these units in the field. My problem is the way they (we) want to sell this to potential clients. I do not see any advantage excavating even a single pass around the unit when I can grab a grinder and have it all done by the time one sets this machine up and is ready to use it.
Now don't think I am throwing off on the machine as very poor or useless, again it has its use.
As for the cutting fluids, if you have ever welded on a part that has just come out of the CNC machine you would know what I am talking about. The fluid or components of the fluid impregnate themselves into the base material and when welded they are released into the weld causing potential problems. One could argue that this might not be as bad with a stick welding application, but we are using orbital MIG machines.
Thank you for your comments and thoughts.
-Jonathan

Jonathan,

I've used profile cutters that vaguely resemble a small saw-blade crossed with a broach. Carbide cutters on a wheel with a specific profile. They can be used freehand in a large die-grinder on aluminum. They are available in a "vee" shape, even in a 75* (perfect for welding). I'm pretty sure you'll have seen similar.

For this purpose, you'd need a "bullseye" for the imperfection, and some sort of chain-vise to clamp a "work table" to the pipe. Then, held firmly, one of these cutters in something like an angle grinder attached firmly to the work table could make a short, precise, and clean cut at the exact point of the flaw. On a 30" heavy-wall pipe, the repair weld couldn't be more than a few inches if you had to go to the root.

Another plus is that it can be used dry, so there's no other prep required... Cut, weld, done.

Just a thought. I can dig up some of these cutters from the McMaster-Carr catalog, if you need an example.

Steve S