Downhill is faster and was the first method of smaw to hit the pipeline back in the 30's so its more refined and better suited for the mainline industry. I've heard of places in texes on center point energy contract that still require oxy. ace. welding. Most of the time its all up to the contractor. I had a russian helper who was a welder in russia and he said everything was uphill. He was a gas distribuition welder. I take it you are talking about the difference of 7018 and 5p, or similar rods?
I work for CenterPoint Energy and you are right, some of our areas still Oxy Acytelene weld. I went to work in Mississippi after Katrina hit and the guys down there still oxy/acyt. weld. I work in Arkansas and I test sma p1 6010 all the way out. I heard of a contract welder who worked for a contractor who never welded with anything smaller than a 1/8 rod, but he came to love welding with a 3/32 6010. Back in the ARKLA days every welder tested on a 45 up hill, all downhill now.
Gotta be carefull when you say PERIOD. Because main line construction, even in the southeast (and there is a huge amount of it going on in that area, late last year and this upcoming year), all predominantly downhill stick. In fact it's looking like the majority of work in '09 will be between Louisianna and Florida.
That said, there's no "big deal" about it, it's just the standard in that industry. Of the several hundred to thousands of pipeline welders I know, I've never met one that could't weld uphill. It's very common to as part of a P/L test to make a LoHi uphill sleeve.
That, plus, in those years when there is no P/L work these guys often work building trades jobs in power piping or process piping. That's the same reason most of them are tig hands as well.
JTMcC.
I'll add that it's a pretty well paying field plus it's a lifestyle that is a lot of fun for some people. It attracts people who like to go places and see things. People who don't like a steady job and don't want to work year round. Who want to work outside.
And you get to know people in the field (not just welders but all of the trades) and you see them in different states on different jobs. It always involves a lot of outdoor cooking : )
It's not for everyone but the people who like it really like it.
JTMcC.
I took a test with Dh LH in Louisiana about 3 months ago. Its a pretty cool rod. It runs pretty much the same as UH LH just the other direction.
Are you speaking uphill the entire process, or just the root/hot? ( with the obvious uphill lo hi following? )
I meant to most and not all places still go up and not down. I've been around the downhill as I have worked on the slope and it does seem faster and easier. Kahunna you are right about the deposition rate. we can do downhill where I'm at just need to qualify a procedure. Might be worth doing for future projects.
when I went to school I was taught all uphill on pipe save for using a few downhill only rods. We were told it's easier to make the transition to DH welding. From my experience that's true.
speaking of pipe welding, the way things are going are putting the pinch on welding engineering work, a lot of the kids I know who are graduating with 4 year degrees are planning on do some rig welding, and pipe-line work. They are putting a lot up all over the state of PA because of all the natural gas they've found
Metarinka same thing I was taught is if you can go up then you can go down and I have met some guys that really couldn't weld uphil but they could downhill now I'm not saying all pipliners are like this just the few that I have met.
I started pipe DH two days ago and we were talking about high pressure gas pipe and boiler code. My teacher used to work for a gas company and said all the stuff was thin wall where the boiler/pressure vessel was sch 80/160. I asked him almost the same question and I was wondering if it had something to do with the thin wall pipe used, putting to much heat in the metal by going uphill and so on whereas with the sch 80/160 the heat will affect it less???
This is an easy question to answer yourself. Take a 4" dia. - .154 wt and weld it uphill then weld one downhill. Do the same on 12" 1/4 wall. You'd be throwing money down the drain going uphill. On a job a couple years ago, I went out to one of our storage fields and they were welding a 16" dia. - 2" wt downhill, now that was taking DH a little too far I think. We're talking open root groove welds on new construction, where the quality of downhill with xx10 electrodes has been proven. In-service downhill is another issue, and that's where LH starts poking in. I had mentioned the 4" .154 wall because we (company I work for) have plenty of that in the ground, therefore we also include it in the welder qualification process.
And, I completely agree with Kahunna on the cut-off being .500 wall. Some books will list downhill on thin wall - less than .375. But DH up to .500 is plenty fast. Again, it's not a quality issue it's speed.
I repsectfully disagree. And this is not an arguement over which industry has better welders. But, I do qualification testing for powerplants and pipelines. Once in awhile there is cross-over as far as personnel. The UP guys usually need a little more practice time when it comes to downhill given the fact they are going to be using much more amperage on the root pass. It's a different skill set, but the uphill guys I've had trying to make the transition see frustration a little more often. Most of the downhillers were also trained uphill, I don't see it the other way as often.
Uphill has the dded advantage on heavier walls of being able to carry more metal and taking more advantage of larger diameters while still being able to control the puddle with less skill as opposed to larger diameter and carryng more metal with downhill.
Down hill is very easy when welding small diameter pipe with 0.125" - 0.188" wall thickness with 60 - 75 degree included angles on vee groove. Time and skill would be required to weld that thin wall uphill at any speed for production.
I don't agree with the ".500 wall being a cut off point". Or I should say my numbers don't.
I've timed quite a few welds on heavy wall pipe up to 1.125 wall over the last few years and downhill is still faster with the rod available now.
I'm aware that Lincoln has put that figure in their little pressure piping handbook since probably before I was born, but I don't think it's accurate today. 5mm 8P+ (or even 3/16" 70+) filling at over 200 amps carries a lot of iron.
All of my comments apply to stick welding in the field.
The new Lincoln DH LoHi has some spooky deposition rates, I'd like to put the stopwatch to a few heavy wall welds using those rods.
JTMcC.
I agree with what your saying. But when you say 'very easy' on wt's .125 to .188 I assume you mean when compared to uphill on those same wall thicknesses. I don't think your implying .125 wall is easier to weld downhill than .312 wall for example. I'm not sure I could agree with that.
Its not a big deal eather way. Im not a pipeliner even though I do weld a lot of it. I have been welding downhill for about 30 years, mostly with 6011 and its just easier for me. 7018 uphill.
I dont know how many times I have had welders come by and see me doing the downhill welding and say I was told you cant do that!
I think its one of those deals eather you can or cant not should or shouldnt.
Couple years back I got slamed and my credability as a welder was in question on a boatbuilding forum from some socalled pro's just because I mentioned I welded outside corner on 12 gage downhill, this was on the cabin of my sailboat. These guys had the same thinking uphill period.
Tom
Well times are slow for us right now and I've actually started helping out between QC duties (welding). So I've tried this down hill alot lately and I have to say I like it alot better. It is faster and I think that for a good welder the transition is not that hard. I'm actually welding to a nonqualified procedure though. Its for expermentation so yall dont get bent out of shape. It is noncritical piping on a chiller. I do hope to qualify a new procedure for us very soon and switch to downhill. Thanks for all the responses.
How can changing your direction cause the rod to melt down faster? Because that's the only thing that will affect the speed of filling in a bevel. You might have a slower travel speed going uphill, but you will also be carrying more metal at the same time.
Now, if you are talking about changing from 5P to 7018, well, that would make a difference in speed, but just changing from up to down would not.
It's not quite that simple ZCat, iron powder in the coating will give you more deposit in the bevels as well, and that puts cellolose rods at a disadventage, but like I said, filling downhill at 200 amps with 3/16" or 5mm rods carries a lot of iron. I don't know of a LoHi stick that can be run at those levels of heat or in those size rods in filling an open butt vee uphill.
JTMcC.
JTMcC, how much metal can a guy deposit with 3/16" downhill? I know that with a 5/32" LoHi a guy can fill an open vee pretty quick uphill. And I know a HortonCBI man that can pile it in uphill with 3/16" LoHi. But against someone welding downhill, I don't know what would be the quicker of the two.
I used to consider it about equal between the two but the clock doesn't lie.
You have to take into account several factors that influence the time spent to make the weld but my take overall is that downhill is faster. In my field dh is the common method and it's also a very production oriented field. So I have a pretty large interest in how many welds are made in a day/week, I probably spend an almost unhealthy amount of time studying this : ), but it really pays off on hard money lump sum work.
The 5mm 8P+ bumps production up over the 3/16" 70+.
Of course I understand there are applications where it's not the appropriate direction of progression, but a lot of times for us it is.
JTMcC.
the ease and weldabilty seem to make it faster. I'm not talking burn deposition rates. It seems to happen easier thats all
interesting, I work in the sheet metal world and light structural, we don't go uphill until thicker than 7ga and even then, not on outside corners. Every sheet metal shop I've been at is almost all downhill, then again this is majority MIG and TIG for cleanliness. I would slam people for running Uphill on gauge work and thin tubing.
Ya its was a sad deal for all the guys involved. There was a lot of interest in this particular boat and most were just wanting to learn to weld and build there own. photo album of all the constuction. Turned out I was a loan wolf at the time on welding downhill. I built it outdoors so I used 1/8" 6011 rods . Then to burry my credability more my procedures were wrong should have used 7018 on the 10 mild steel hull and I was taking a risk that my welds could cold crack. Notin like confusing the guys that wanted to learn.
I hate to think of the mess an amature welder could make welding uphill with 7018 on 10 and 12gage, All because somone told them that was the correct way.
Tom
yah there will always be people who think they are right, 7018 on an outside corner joint on 10 and 12 gauge really doesn't seem appropriate. Also my guess was it was low carbon steel? Hydrogen diffusion is based on carbon content and material thickness. you shouldn't need a low hydrogen procedure for 10 or 12 gauge mild steel.
Usualy in steel boat construction an A36 grade mild steel is used and thats what I used. If welded correctly 6010,11. or 13 work fine. stronger than aparent metal. No benefit going to 7018. I have heard of people welding downhill with 7018 but have never tryed it myself , usualy when I run it I have never had any reason to try to switch from uphill.
Tom
If a person cant go uh and dh then he isnt complete. I have to go uh inside the plants at work and when called out on the line its dh. When the time comes I have to break out my tig. I to am from the south east. Most dh welders are good uh welders, however on the other hand most uh welders think they are good dh welders.
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