downhand vs uphill 2

[sftyvlv]

I have asked the question "downhand vs uphill" progression on root,fill and cap passes,when welding pipe. Why do "pipeliners" run down and process and power piping welders progress uphill, what is the difference? No one seems to be able to help.
Can you please give me an explanation?
Sftyvlv

 

[GregLamberson]

I can tell you the resaon pipeliners run downhill - it's faster. On pipeline welding, occasionally you will see tie-ins done with an uphill root and maybe hot pass and the fill & cap downhill. But predominately it is downhill because of the speed.

But to your real question of why and what's the difference - I am curious to see the reason as well and will wait for BigInch or Metengr to enlighten us.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[deanc]

Your pipeliners run the final passes uphill. The downhill root ties in nice with minimal internal undercut.

Downhill also works good for seal welds....air casing,etc.

Always went by the old rule of thumb that a downhill is 7 times weaker then a uphill.

If you do sections and etch,one will see the difference.

Really depends on what you want in the end. You can always find some welder that can run any position with any rod, depends if the WPS allows and they can qualify.

 

[GregLamberson]

I beg to differ, you will see occasionally some pipeliners run uphill, but 95%+ of pipelines are welded downhill - bead, hot pass, fill & cap.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[deanc]

Greg

No problem. I have seen all kinds of things and yes to the downhill.

P5 root,7010 fill and cap all downhill. Been some places where the wind was so bad you could not use any Lo-Hy anyhow.

Back to the WPS and what the welder is qualified for. X-ray,bends. What does the job require?

If you want a answer run test coupons,section and etch. There will probably be some difference pulls between the up vs down.

 

[stanweld]

When welding with the SMAW process, the vast majority of process and power piping is welded with low hydrogen electrodes (EXX18) which are "uphill" electrodes. Pipeliners for the most part use EXX10 electrodes which can go up or down.

Full penetration root beads are more readily made with EXX10 electrodes in the downhill direction largely because the welder can "push out or dress" the root pass with the hot pass because the root is thin (also see deanc's comment). When welding the root in the uphill direction with EXX10 electrodes the root cannot be similarly "dressed" because it is too thick. One problem regarding the thin weld deposit is root bead cracking when the hot pass is not performed very shortly after depositing the root pass or appropriate preheat has not been applied or a combination of both.

In the 1960's and early 1970's, it was not uncommon for root beads to be made with E6010 electrodes in the downhill direction in the process industry. In the early mid '70's a major oil company prohibited this practice, requiring all weld passes to be made uphill and this requirement soon became standard practice in the process industry.

In terms of weld completion rates, weld metal deposition rates are based on electrode diameter and current, not travel speed. It really doesn't matter which method of progression is used if the electrode diameter and amperage are essentially the same.

 

[MJCronin]

Excellent discussion...!!!

 

[unclesyd]

One little point: when referring to pipe welds the preferred terms are "Vertical up" and "Vertical Down". Downhand and uphill can have entirely different meanings when it come to welding.

Vertical Down:
Low penetration
Concave bead
Slag
Problems with hot short materials
6G coupons don't qualify for Vertical Down (may have changed)


Vertical Up
Good penetration
Requires a little better technique
Better for poor fit ups and wide welds

 

[JTMcC]

My goodness there is a lot of wrong information here.

deanc, pipeliners DO NOT run "final passes uphill". "Downhill 7 times weaker than uphill"???? please take a close look at the mechanicals of the downhill pipe rods, 6010's, 7010's, 8010's and 9010's in use.

Pipeline welding isn't 95% downhill, it's more like 100% downhill when using stick. Some dual shield procedures are being used on tie ins for automatic jobs and that of course is uphill. The flux core wire being used sometimes on automatic tie ins is a downhill wire.

deanc, P5 hasn't been made I'd guess in over 40 years.

The terms used in the pipeline industry are downhill and uphill. Downhand of course is a weld made on plate in the flat position.

Manually welded pipelines are welded downhill because of the speed factor.
Todays downhill pipe consumables (primarilly Lincoln's "Pipeliner" line) are pretty highly evolved and allow a lot of iron to be stacked in a short time, as I said the mechanicals speak for themselfs.

The pipeline construction industry is one where the question asked is "how many miles did you lay today", production is king. And it's an industry thats been around long enough that the process is pretty efficient.

This of course applies in the U.S. on mainline transmission lines. The related segments not generally considered pipelining such as oil field gathering system and town distribution system construction follows pretty closely the techniques and procedures used in mainline construction.

JTMcC.

http://www.firstratefabricators.com

 

[JTMcC]

I'll add,

unclesid,
There is no "vertical" in pipe welding (or overhead or flat for that matter), there is of course in plate. Pipe is welded either uphill or downhill progression.

We make full pen welds daily on pipe in downhill mode. Your reference to "low penetration" again applies to plate, 100% is 100% regardless of up or down.
Your reference to "concave bead", a concave cap is rejectable and cause for a weld repair on every job I've welded on. Convex caps are made all the time.
"slag"??? what about slag, trapped slag is a repair as well. And I don't have any idea what "6G coupons don't qualify for vertical down" means. I've taked well over 100 downhill pipe tests on a 45. That's pretty much a standard pipeline test along with a hand cut 12" on 12" inverted branch weld.
"Uphill requires a better technique"??? where do you guys come up with this stuff??!!
I've got 20+ years experience in both downhill and uphill pipe welding and that's just not true.
Shame on you guys putting out stuff you don't know or understand.

JTMcC.

http://www.firstratefabricators.com

 

[GregLamberson]

JTMcC

I said 95%, you're right, it's probably more, but I have been on a couple of projects where Spie-Capag have wanted to do an uphill tie-in procedure, Chad-Cameroon was an example. They did some uphill tie-ins on some of their 480 kms.

But otherwise, if it's stick welding, it's all downhill, again as mentioned, because of speed. On the other Chad-Cameroon spread of 640 kms, there was not a single uphill weld made.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[sftyvlv]

Thanks for the imput gents.
Could anyone give a metalurgical explanation as to which is a better weld (if in fact it is) and why its accepted in gas transmission lines and not in power and process piping using manual and semi auto welding processes -SMAW GMAW (thanks JT I should know uphill, downhill terminology).
Sftyvlv

 

[JTMcC]

GregLamberson,

That's why I made a point of saying my information applies to Mainline construction in the U.S.

I realize there are other parts of the world where different techniques are in use.
I'm always interested to learn what is being done across the globe in this field. Any info you're willing to give I'm happy to hear.

Regards,
JTMcC

http://www.firstratefabricators.com

 

[metengr]

The comments above have been interesting. If you really want to understand a true comparison between uphill and downhill welding positions related to specific welding processes, and the effects on metallurgical properties, I would suggest you visit the web site below and download the Welding Handbook by Kobelco;

http://www.kobelcowelding.com/PDF/handbook2004.pdf

 

[unclesyd]

I can't decry anyone who has taken 100 tests in 20 years, though it does seem strange.
I know pipeliners can weld sometimes but in my 42 years in and around pipe welding I've yet to see more that 20% walk in and pass a test. Far less if they were testing for CRAS.
I still standby my statements concerning the aforementioned weld processes. Though I will temper it somewhat by the fact most of my experience has been with in the power and chemical industry.

By the way the little "Red Rod" is still alive and weld.

 

[JTMcC]

unclesid you posted information that was flat out wrong. Your responce is to try to insult an entire group of welders. That speaks to your investment in your internet image more than it does to and form of welding.

Considering that every job is a test in my world, 100 tests in the span of 23 or so years isn't much, and considering that many jobs call for multiple tests (we worked for a particular gas company for several years that required like all gas companies retest every 6 months, that called for 8 tests every 6 months. That's of course 160 welding tests in the course of ten years. We've worked for dozens of gas companies so really my number is a bit low.

I only intend to correct missinformation on a topic we live and breath, not to threaten your supremecy of the interweb.

Every comment I've made is true and easily verifiable by anyone with an internet connection. You were wrong.


JTMcC.

http://www.firstratefabricators.com

 

[unclesyd]

I didn't insult welders and never would as I've also been associated with good welding my entire career, in fact my life and sevral thousand others depended on it.

As you state your experiences all I was doing was stating mine when it comes to welders and procedures. I'll concede that you have seen more welders come and go than I but I can pull up my records of around a thousand welders that worked for us over the last 20 years. These records give their pedigree and all qualifications along with all RT results or their period of employment. We require 100% RT on 80% of our piping.

By the way at my age bettering my image anywhere is the last of my problems.

 

[Welder4956]

"deanc, P5 hasn't been made I'd guess in over 40 years. "

Are we talking about Lincoln's Fleetweld 5P or was there another one called P5? Lincoln still makes Fleetweld 5P.

Good discussion and good example of people's differing perceptions based on their experience. I don't have any pipeline experience, only power experience. In the power industry, a EXX10 is only used downhill for root passes in low energy, low temperature systems, such as service water, fuel oil, coal or ash piping. With steam systems that have much higher pressure and temperature than pipelines, low hydrogen alloy steel electrodes are a necessity and they do not weld well with downhill progression.

 

[JTMcC]

P5 was the precceded 5P and 5P+, it had a white coating and hasn't been made since I believe the mid to late 60's.

Temperature is rarely a factor in cross country line pipe.

What pressure is your steam running at?


JTMcC.

http://www.firstratefabricators.com

 

[Welder4956]

Main steam supply to the turbine runs at 1000 degrees F at pressures ranging from 1000 psig to 3900 psig, depending on the type of boiler.