Coke Drum manufacturing by MAG Welding

Date 02-29-2008 14:21

Are you able to rotate the drums and, if so, SAW may be a better choice? More info on your capabilities may help get more informative answers.

By jiweiming (**)

Date 03-01-2008 13:13

We can assemble the first and the second cylidrical shell vertically, so we can weld the circum seam by horizontal SAW. Then the third and the forth. However, When we assemble this two big shells, we have to assemble them horizontally and they can not be rotated, so we have to weld them all position by SMAW. Now, we shall reprove it, so we are scheduled to weld it by MAG or FCAW. How do you think of it? Thanks.

By G.S.Crisi (****)

Date 02-29-2008 22:56

The circumferential (horizontal) welds should be done by two welders working at the same time and located 180º apart, or four welders at 90º apart.
The longitudinal welds (vertical) should be done each one by a different welder working upwards (uphill) at the same time.
Do the first (nearest to ground) circumferential weld and then the second (the 2nd nearest to ground).
Then do the first (nearest to ground) vertical weld. After this, do the 3rd. circumferential weld and afterwards the 2nd vertical weld.
Go ahead up until you've welded the whole drum.
Giovanni S. Crisi
Sao Paulo - Brazil

By jiweiming (**)

Date 03-01-2008 13:15

Thanks, Crisi. But my question is whether we can weld it by MAG or FCAW?

By 803056

Date 03-02-2008 18:05

You can use either pulsed GMAW or FCAW. You can not use MAG (GMAW) spray mode transfer out of position.

I would prefer to use FCAW, but like all things related to welding, there is no one method that is "best". You have to select your consumables carefully.

Best regards - Al

By jiweiming (**)

Date 03-04-2008 02:34

Thanks,AI. But KOBELCO recommend me use spray mode transfer with pulse MAG(GMAW) for its solid wire MGS-1CM for all position welding for pressure vessels welding. As for you, why we can not use MAG spray mode transfer? Many thanks.

By G.S.Crisi (****)

Date 03-02-2008 19:28

What I've said refers to the welding sequence, which you can follow using either SMAW, FCAW or GMAW. According to Al, spray MAG is not recommended.
Giovanni S. Crisi

By 803056

Date 03-04-2008 02:59

I assume MAG is what we here in the US refer to as GMAW. If I'm wrong, please correct me.

GMAW using spray mode transfer produces a very fluid weld puddle and is limited to flat grooves and flat and horizontal fillet welds in most metals (aluminum being an exception). If you can "roll" the drum as you weld such that the groove is in the flat position, by all means use GMAW spray mode transfer. The process produces a deep penetrating, fluid puddle that wets in nicely. Provided you select the filler metal carefully you should be in fine shape with regards to mechanical properties.

However, if you need to have the capability to weld in all positions you will have to use GMAW pulse mode or FCAW with the electrode to provide the versatility you need. GMAW using short circuiting transfer is asking for problems with fusion type discontinuities because it produces very low heat inputs.

I would give strong consideration to FCAW because it does utilize a flux system that improves deoxidation, a slag blanket that reduces the cooling rate, and with careful filler metal selection it can produce good mechanical properties.

However, if the manufacturer has provided specific direction, you need to give their recommendations serious consideration.

Best regards - Al

By G.S.Crisi (****)

Date 03-04-2008 21:01

Al,
MAG means Metal Active Gas and is the old designation (although still widely used) for GMAW.
The difference between MAG and MIG (Metal Inert Gas) is that in MIG you use Argon or a mixture of Argon and Helium as inert shielding gases, whereas in MAG you use a mixture of Argon and Carbon Dioxide (an active gas).
Giovanni S. Crisi

By 803056

Date 03-04-2008 21:38

Thanks for the up date. I was never sure of the exact nature of the welding process when the MIG, MAG designations were used. Now I know. Thank you Giovanni. A little more information to tuck under my hat.;)

Best regards - Al

By MDG Custom Weld (***)

Date 03-05-2008 16:04

MAG in Europe is the common slang that MIG is in the states, and as we all know it's all just GMAW