American Welding Society Forum
Vertical up vs vertical down: is one preferred over the other? We are getting a carbon steel shop-fabricated tank made for water service and the fabricator is proposing vertical down welding. The welds are to be double sided. Would this joint design make a difference? I have seen for pipe welding vertical down for the 6010 root and vertical up for the 7018 F/C.
I'll keep it short, I got a baby crying. Root, hot, and fill passes are generally done down hill with 5p. Your Low hydrogen, (7018), cap should always be uphill. The gurus on this site will fill you in on why and how. Baby needs a bottle. . . . .
Generally I would say vertical up is preferred over down for most applications by alot of people. Certainly deep penetrating (F3 group) stick electrodes are reasonably foregiving and capable of excellent welds with a downward progression. And a really good welder can probably weld about any process and electrode downward successfully if they are well skilled and really determined to do so. And downhill is an excellent way to overcome burn-through problems on thin material. However I am generally skeptical of downhill welds. Few welders have done enough destructive testing of their own work, on various metal thicknesses and joint types, to know for sure if they are getting reliable fusion and internally cleans welds downhill with short-circuit MIG, 7018, E71T-1, etc. Due to the faster travel speeds necessary, lack of fusion, porosity, and inclusions are considerably more likely than if done uphill.
Most low hydrogen rods aren't made for downhill. There was discussion last year about this. There's really noway to insure that you wont trapslag running it downhill.
When I was a lad in trade school, I was taught to run my root with 5p uphill. The only problem I have with this is running out of your puddle then coming back into it on the root. Running a root down hill allows you to crank that heat up and really penetrate, without running away from your puddle. I've passed many xray and bend tests using this method. I dont do much structural work anymore, so the uphill teqnique may be better on that application, I don't know for sure. I do know that on many structural jobs the process calls for low-hy only, no 5p is allowed.
There's some guys in here that can give you a text book answer on this one.
I will pull out AP!-650 which does allow downhill with 5P and I am sure I will find in it, that 7018 can be used downhill for capping as this was the way I helped build many many water towers, sandpipes, and flat bottom water storage tanks.
Sorry man, just giving my experienced opinion, just like you. I have run 7018 down hill, but had to run at such a temp that there was no possible way to form an actual "cap" It was more like a flush hot pass, and to me that does not offer any tangible strength to a weld. Before we both get hotheaded, lets ask John Wright what the answer is. . . .
Sourdough is right in his statement that "most" 7018"s are not made for vertical down. There is one variety (classification) that has been mentioned on this forum before that is made for vertical down but I will personally stay well away from 7018 vertical down.
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