uphill benefits

Date 09-12-2008 14:37

hmmmmm....

Sometimes people weld downhill on plates, as well as on pipes.
Yes welding is related the the fusion process :)

3.2

By Sourdough (****)

Date 09-12-2008 16:02

Are you welding out with low hydrogen?

In 1990 when I got my first 3g/4g cert I was taught to run my 5p root uphill. I'm not real sure why, because I haven't done it since. I have never run into a single process that required it. There are no pipeline companies that would require any pass to be uphill, unless you were running low hy. There are no structural applications that would allow you to run anything but Low hy uphill.

Now, if you are running low hydrogen rod, you will definately be required to run it uphill. There are low hy rods made for downhill, but I have never seen them in my 20 years of professional welding.

Low hydrogen rod can trap almost 50 percent of your slag going downhill. And running lh down hill will not give you any penetration or fusion, no matter how hot you are running it.

This is my 2 cents. There are some guys on this forum that may give you a technical answer that might help you more...........

By JTMcC

Date 09-12-2008 16:34

That's just not true.

There are structural applications that are welded downhill, particularly in light gage metal framing.

Downhill progression is prequalified in partial pen tubular joints, in other situations you have to qualify your procedure, We are in the process of doing that right now. My knowledge is limited but this is my current understanding and I know there are people here who have a good grip on this that will correct me if I'm wrong.

LoHi has been used off and on in the pipeline industry downhill, with fine penetration and fusion, and without trapping slag.

Just because I've never seen it, doesn't mean it doesn't exist, it's a very big and broad welding world out there.

JTMcC.

By js55

Date 09-12-2008 19:15

5P uphill. Wow! Not much of that goin around these days. It was used extensively in industrial work prior to 80's for roots and some F and C. Thats how I started. Get a little keyhole by eating the landing, step back deposit, step up, eat the landing, get a little keyhole, step back and deposit, looks like you knocked over a stack of dimes when done right. And you are certain you are gettin the edges and penetration because you can actually see it while its happening. Right after my apprenticeship everyone switched to GTAW for roots in industrial work. And 5P uphill F and C disappeared off the face of the planet for all I know.

By Sourdough (****)

Date 09-15-2008 14:40

I'm talking about 90% of pipelines. Please show me a (gas) pipeline company that uses lh.

By pipeliner 798 (**)

Date 09-15-2008 03:38

process pipeing with 5p bead it is uphill in all my experiance, its usually gtaw now, but when i broke out in the early 90s we still did a lot of 6010 beads.

and also you can run 7018 dh, iv tested for it when i worked for cb&i, its used mainly for a wash pass on capping but we had to test on 1/2'' plate with 7018 dh all way out

By Metarinka (****)

Date 09-14-2008 04:37

It has to do with penetration, slag inclusions, etc. You didn't say what process you were running but for example MIG and tig have problems interms of good fusion when welded vertical down. however if high penetration is not needed such as in sheet metal or thin gauge then vertical down is generally picked due to the time savings.

I could be mistaken but when following low hydrogen procedures I thought uphill was choosen as it's generally slower allowing more time for hydrogen to diffuse from the weld bead.

Sometimes is due to the nature of the weld bead and whether or not it will form a shelf, or needs as shelf etc.
also some processes have greater deposition rates in a certain position, or can be achieved in fewer passes vertical up so it's a matter of economics

however I specifically remember GMAW procedures calling for Vertical up due to penetration and complete fusion at the root issues. I also remember learning every process vertical up as I believe most people would agree vertical down is generally easier

By swsweld (****)

Date 09-15-2008 02:34

I welded for 15 years without burning a 6010. In boilers and nukes we NEVER used them. It was always GTAW/SMAW root/fill & cap. Sometime GTAW all the way. In commercial buildings (hospitals, colleges, high schools, barracks, prisons, etc) we use 6010 uphill all the time on mechanical piping (HHW,CHW,Steam and condensate) Sometimes RT/UT is required and 6010 uphill and 7018 fill/cap uphill is the norm. If the acceptance criteria is more stringent than the standard ASME B31.1 that commercial building often fall under I will use GTAW for the root/hot pass and 7018 it out.
You could weld it d/h with low/hy if you submit a qualified welding procedure and it is approved by the PE.

I have seen CBI weld the containment wall of the reactor building (1/2"thk) downhill with low/hy. in the early 80's. It can be done.

I think the pipeliners use 6010/7010 d/h for speed. They use high amperage and travel speed to complete welds faster. There may be some mechanical and metallurgical reasons also.
I think heavy wall is welded uphill most of the time. I am not a pipeline welder so I don't know if they use any HW pipe.
We have welded HW 360 uphill/downhill using machines.
As JTMcC stated "it's a big and broad welding world out there." I thought I knew a little bit about welding until I joined this forum.
One reason low hydrogen is welded uphill on structural is the deposition rate. You can carry more metal uphill with moderate heat input.