Oxyacetylene welding on high stress pipe

By mjw Date 05-05-2014 16:32

We have procedures for oxyacetylene welding on low stress pipe (both butt and fillet) following DOT CFR Appendix C. I cannot find anything for welding on high stress pipe (X52) using oxyacetylene welding and I am curious if there might be a metallurgical issue or concern. This is all related to API5L no longer allowing dual stenciled X42/X52 pipe and being told X42 soon will no longer be available. I need reasoning to either dismiss oxyacetylene welding on X52 pipe or make a new procedure following API for this.
Thanks for any input

By 803056

Date 05-05-2014 21:54

Qualify the WPS.

Al

By js55

Date 05-06-2014 13:46

Not so sure about X42 no longer being available (and there are even lesser grades). There is still great demand for the material. The cross country pipelines that drive thinner walls and higher strength are not the only application of the steel.
Having said that, you need to be cognizant of the process by which the X52 or other steels achieve their strength. They have systematically decreased carbon and increased alloying and in many instances will use quenching and tempering. I would suppose that the heat input of OAW would not lend itself to a viable procedure for these materials.

By OBEWAN

Date 05-06-2014 15:14

Seriously? You mean they still use OF processes on pipe - aside from brazing or silver soldering? Has the SMAW and inert gas process world come to an end?

I have an ancient book on OFW welding of pipe in my collection - but have never seen it done aside from silver soldering.

I am left wondering how my ancestors did at all - back in the day.

By js55

Date 05-06-2014 15:37

Given the difficulty perhaps therein lies an argument for devolution.

By Lawrence (*****)

Date 05-06-2014 15:38

This was my thought, but I wanted to let the conversation roll a bit before I tossed the wet blanket :)

I discovered about a year ago that some local gas companies still do a good bit of OFW field work.

Not knowing all that much about the situation I can't say OFW is bad... It's portable and there are prolly an army of old salty dogs that don't want to do anything else.

But GTAW--GMAW--and Self Shielded FCAW would seem to be faster and more consistant alternatives for fab and field. (on the outside looking in)

By PlasmaHead2 (***)

Date 05-06-2014 21:36

I've found a forum of sheet metal workers, the guys who make car panels and hoods and the like from scratch...
LOTS of them still use OAW for body work on aluminum of all things. Most seem to swear by OAW and at the gas shielded arc processes.
The claim is that OAW welds are stronger, but something tells me its strength is that OAW anneals the sheet in a wide area compared to GTAW. Which is great when they procede to smash the weld and surrounding area flat with a hammer.
Sorry, not about pipe...

By 357max

Date 05-06-2014 16:26

OFW Pipe with a 1 1/2 X Carburizing flame vertical down with the filler wire trailing the flame. Fast with the carburizing flame an addition of carbon for lower melt temp & therefore faster speeds, PGE CA used to weld 4 inch and under for facility connections. There are a few utility companies use this process.

By mjw Date 05-06-2014 15:57

We are a local gas company and still use OAW along with stick and wire in the field. It is a proven process but with much more plastic installed and that we are being told by major pipe manufacturers that the demand for X42 pipe is dimishing and will only produce it if you buy the entire run. That being said and without going into great detail, I can qualify a new procedure on high stress pipe but not sure if it is worth it.

My main concern was making this weld on high stress pipe. If I dicontinue its use I need to provide a case to our company that everyone can agree to.

By js55

Date 05-06-2014 16:19

The demand for X42 may be diminishing due to the use of the higher strength alloys and TMCPAC alloys.
But to say it will no longer be available is like saying carbon steel will no longer be available because of Grade 11 or 22.
We utilize X42 all of the time and it is maintained well in stock 'on the shelf' so to speak.
Of course, we don't buy from manufacturers. We buy from distributors who buy from manufacturers.

By js55

Date 05-06-2014 16:21

Of course, the irony in this thread is that the TMCPAC alloys replacing the X42 are the very thing that will drive OFW out.