7018 has a tendency to close the gap has you weld. The technique that our welders use is stated below:
1- 4 tacks @12;6;3;& 9
2- start first to weld from 9 and progress to 10:30, i assume this will be your first stop.
3-now go down to 6 and progress to 4:30, this will be your next stop.
4- next complete from 10;30 to 12
5- next complete from 3 to 12.
6- complete next from 4:30 to 3
7- last complete next from 6 to 9.
If you start form the bottom and go to the top, quite often the pipe will draw together and you will have difficulty getting penetration on the upper half.
To get good penetration progress upward moving the rod forward, now the walls of the pipe will get molton, just withdraw the electrode for a moment back into the crater (do not whip). This will give the forwarding edges a split second to cool, as you progress. Keep the same pace.
Need more info. Do a search on 7018.
Good luck!
DH
As a general comment, getting hostile or rude serves no one nor a given purpose. It's my experience that all groups ( welders, inspectors, fitters, and everything in between ) can help each other far more than they have been the past few years. The number of skilled welding, fabrication, and inspectors, have been on a steady decline for some time now. Part of the reason for that in my eyes, is the negative attitude displayed by each group toward another, and within each group individually. It's hard enough to find a young person willing to work these days, and then when you do, the last thing they need to be seeing is a bunch of old farts going at each other. These young folk like it or not are necessary for the continuance of our world as we know it and the world of the future. I suggest we help them in any way we can in a courteous and professional manner, without resorting to negativity, condescending attitudes, and infighting. Young folks starting out or even older folks changing careers, tend to question what they are letting themselves in for when they see and hear things like that.
I myself find that I learn from such people. No ones told them they can't do it, or it's impossible, and from time to time they come up with a solution I've never seen before.
I've worked to different codes/standards around the world, and I can assure every reader, for every way you can think of to acomplish a given task, theres likely to be 10 others out there somewhere you've never heard of. No body ever reaches the goal of knowing it all, no matter how much experience they have.
Just a few long winded thoughts for consideration.
I ran into the same situation several years ago and was lucky enough to work with some Scotts fellas fresh from the oil rigs in the North Sea where this is the standard procedure. The 7018 Root pass instead of conventional 6010 takes some getting used to. But like all welding there are little tricks. First I woulduse a 3/32" Land and Gap, now the "trick", use DC- for the root. Yes! Straight Polarity for the root. It will give you a very deep penetrating weld but you will not see a keyhole like you do with 6010. I like to use a hacksaw with (2) blades side by side to feather the both side of my tacks and the end of each pass. You will have no problem getting in a root this way. Be careful some inspectors are fussy and will make you adhere to the DC+. Just switch the cables around without anyone looking. You will notice a different sound, but the root will go in great.
Or maybe prove this out and revise the procedure hence some state and federal standards aren't just a "guideline" as mentioned above. I know what you are saying, but this would have very costly fines/discipline in some areas.
Hi Rick, I hope you are only a rookie and not somebody with years of experience. Teaching those new welders dishonesty in the work place could cost them their job. The welders in our union do hundreds of 7018 root passes each year with no problem. If the procedure calls for 7018 root pass, then that means somebody had to do the qualifiing procedure, so therfore, all other welders should be able to perform the same welds.
Hello guys,
I have previously spent 15 years as a pipe welder with the majority being GTAW root - E7018 fill & cap / E6010 Root - E7018 fill & cap / and E7016 root - E7018 fill & cap.That is why I asked (in an earlier posting) about the E7018 root in the US / Canada as I had never heard of it before.
I also stated (in an earlier posting)that in my experience E7018 should not be used on DCEN. This was based on past experience filling and capping where you generally always ended up with a substandard run full of porosity.
After doing some research on this I will admit I was wrong and certain E7018 electrodes are made to run on DCEN (root runs only).
I am using Australian electrode manufacturers recommendations but I don't think they differ greatly from your side of the world.
E7018 DCEN/DCEP or AC (preferred polarity for filling & capping is DCEP)
E7018-G DCEN/DCEP or AC (preferred polarity for filling & capping is DCEP)
E7018-1 H8 DCEP
E7018-1 H4 DCEN/DCEP or AC " The 2.5 mm 18TT is a special root running electrode displaying excellent AC arc stability down to 55 OCV and smooth DCEN performance in wide root gap preparations."
AWS D1.1 Table 4.5 (13) and ASME IX QW 253 (QW 409.4) both state that change of polarity is a non-essential variable for the WPS.That means that you can qualify the procedure with the root run DCEP and at a later date you can then run the root run with DCEN without requalification of the procedure.The same for welder qualification, if they qualify DCEP they can put a root run in using DCEN without requalification.
On my PQRs I have the polarity used during the PQR test and on the WPS I have DCEN/DCEP with a note stating "as per manufacturers recommendations."
Regards,
Shane
API 1104 18th 2.4.2.7 "A change from DCEP to DCEN or vise versa or a change in current from DC to AC or vise versa constitutes an essential variable."
This is for procedure qualification. The 19th edition would be 5.4.2.7 and not sure if criteria is the exact same - but I believe it is.
jarsanb , thats the way i read it . 5.4.2.7 electrical characteristics . i havent got my new 20th edition ordered yet . willie