What is the best way to weld DN 2000 Steel Pipes

By Stephan (***)

Date 09-06-2009 21:58

Polka,

have you already considered semi-automatic girth GMA-Welding?

For instance, see also:

http://www.crc-evans.com/globe.htm

Stephan

By pipehead (***)

Date 09-07-2009 03:25 Edited 09-07-2009 03:30

what diameter lines are we talking? Open root or lap joint (bell and spigot)? uphill or down hill on the 5p? also what type of code aws, awwa(american water works ass.)? because if it is a awwa code there are a number of pre-qualified procedures. Especially for open root 5p and gmaw fill and cap type setups.

By Stephan (***)

Date 09-07-2009 06:14

pipehead,

forgive me to reply in regard to the material designations before 'polka' did.

He is talking of a European former valid but meanwhile unvalid steel grade 'St37' (DIN 17100) which is referred to as 'S235-..' according to DIN EN 10025 nowadays. The material is comparable to an ASTM A 283 Grade A,B,C, to the best of my knowledge.

The diameter he is referring to is a DN 2000 (Nominal Diameter) in millimeter dimensions. I.e. 2000 mm ~ 78".

Stephan

By pipehead (***)

Date 09-08-2009 02:22

Stephan,

Ah I figured someting of the sorts.....it had to be a european grade......do you know the joint configuration? open root or lap which is the most common on that size of line here in the U.S....

That is also the common grade of the two larger pipe suppliers I've worked with. And our process is dual sheild GMAW, sometimes with a 5p root, or on smaller pipe 60" diam. and smaller 5p downhill with as large as 7/32" or 1/4" rod.

But then again its back to the joint and spec.

By Stephan (***)

Date 09-08-2009 07:01

pipehead,

thanks for the response that contains interesting information - at least for myself!

Hmmm... unfortunately polka isn't in the mood or hasn't enhough time apparently to provide us with more details.

Thus, once again, please let me reply by interpreting polkas post from my personal standpoint.

As far as I may be wrong with this, he may correct it later on...

I guess from the data he supplied (quote):

"We weld them with using 3.20" and 4" 6010 electrodes and 3.25" and 4" 7018 electrodes..."

as well as by:

1.Root Weld: 3.20 mm 6010 electrodes
2.Hot Pass: 4 mm 6010 electrodes
3.Multi Pass: 3.25 mm 7018 electrodes
4.Multi Passes: 3.25 or 4 mm 7018 electrodes

... we may suppose - unconsidered the inch designations with the first named electrode diameters - that it's an open root application. Very often a standard V-Bevel joint configuration (30° bevel angle = 60° root opening) is used for those kinds of applications -at least here in Germany - as it makes the fewest 'problems' to being easily prepared.

Even though, an appr. 78" diameter is rather not an everyday application, honestly spoken.

So, provided a 60° root opening, an 18 mm thickness and supposed they're using a 2 mm gap width, we may calculate (A = t * w + t² * tan alpha/2) a theoretical seam cross section of 246 mm². This along the pipe's circumference... that's plenty of work and time needed to finish the joint. :-)

From this standpoint it's well understandable that they're searching for an improvement.

However, that's all based on assumption. Hence, it would be great if polka would provide you a/o us with some more information or could clear this up a bit more in detail.

I'm sure you would be the absolute right one, to point him in the right direction with this interesting application.

Thanks!
Stephan

By Polka Date 09-08-2009 11:25

Thanks Pipehead and Stephan.I will try to fill the blanks that you left to me now.Pipes are 80" diameter.As you told already they are V beveled.Our pipes have 60° root opening.As we are using 3.20 mm e6010 electrode we need minimum 4 mm gap width to get a root.Total 5 passes of weldings are required to weld these joints.In these weldings we use 120 pieces of 3,20 mm e6010 electrode 35 pieces of 4 mm e6010 electrode.330 pieces of 3,25 mm e7018 electrode and 170 pieces of 4 mm e7018 electrode.

By Stephan (***)

Date 09-08-2009 12:24

Polka!

That's awesome!

Brings me back to:

"...provided a 60° root opening, an 18 mm thickness and supposed they're using a 2 mm gap width, we may calculate (...) a theoretical seam cross section of 246 mm². This along the pipe's circumference..."

to be continued by your statement:

"...we are using 3.20 mm e6010 electrode we need minimum 4 mm gap width to get a root.Total 5 passes of weldings are required to weld these joints.In these weldings we use 120 pieces of 3,20 mm e6010 electrode 35 pieces of 4 mm e6010 electrode.330 pieces of 3,25 mm e7018 electrode and 170 pieces of 4 mm e7018 electrode..." .

That's truly a lot of 'stuff' to be deposited...

Thanks for the feedback!

I am curious what 'pipehead' (or the others) will say to this.

But anyway, following to my very first post to this topic. Using semi-automatic GMA girth welding with special bug & band systems (e.g. CRC-Evans, but also others, e.g. RMS, SERIMAX etc.) may allow you to reduce the seam cross section drastically, e.g. by using a particular and narrower gap design. Thereby you are allowed to save time and filler metal, and very often improve the joint-quality.

Best regards,
Stephan

By pipehead (***)

Date 09-08-2009 15:37 Edited 09-08-2009 15:44

hey thanks polka....open root oon 78" thats a chore....!

especially with that size rod! Have you tried stepping up the rod diam....once you've placed the root pass? or like I said it's now very common here in the U.S. to complete your root and hot pass then run GMAW the rest of the way out....it sure speeds it up!

Or possibly a semi-automated system? like steph said a bug type system would probably work well other than i take it these pipes are all ready in place which makes sometimes hard to acess.

another thing I have experienced on pipe of that size with open root application is the fit up is not very good because most of the time that size pipe tends to be "egged" or out of round which makes it hard to allign just right.

hope this helps.....good post

By Stephan (***)

Date 09-08-2009 16:40

pipehead,

"...good post..."

Well said! :-)

And... good points coming from you!

By Polka Date 09-10-2009 17:36

GMAW machienes are very expensive especially if you buy this machienes only for this job.Instead of one Automatic GMAW machine we can multiply 3 times our smaw welders so we get the same production rate.We plan to use all sellulosic electrodes in our further welds (eg e8010 5 mm electrode after e6010 3,20 mm electrode.) Any suggestion with electrode type and electrode size and welding order?

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

Date 09-10-2009 22:49

Polka,
I don't understand you. Your first post says that you're welding the 2 meters diameter tubes using covered (or stick) electrodes but this takes too much time and so you asked for suggestions to reduce the welding time.
Then, Stephan and Pipehead recommended you to use semiautomatic GMAW (or MIG) welding to speed up your job.
But now you come up saying that a MIG machine is too expensive in your country and so you'll increase 3 times the number of welders and that will speed up your job at a lower cost than buying a MIG machine.
My question is this: if you knew what you were going to do beforehand, why did you ask the question?
My personal opinion:
go ahead with E 6010, 3,2 mm electrodes for the first pass; E 7018, 3,2 mm for the second pass and E 7018, 4 mm for the subsequent ones.
Giovanni S. Crisi
Sao Paulo - Brazil

By pipehead (***)

Date 09-11-2009 01:01

Polka,
We don't run strickly gmaw machines we run ln-25 lincoln feeder boxes off our stick machines...they are simple and low maintnence...and you can find a used one for about 600 U.S.....

But if stick is your only option......Of course go with bigger rod......and down hill will cut time in half!

Why 8010?
Why not 7010? in like the 5mm to 6mm down hill (if it was me)

I did a job about 3yrs ago that was 66" 6010 root and hot pass 7010 fill and cap 1/8" or 5/32" for the root and hot pass, 7010 7/32" for fill and cap, and I could weld a complete joint by myself in well under 4hrs... how long is it taking you guys?

By pipehead (***)

Date 09-22-2009 01:44 Edited 09-22-2009 01:49

Stephan,

Here's why we don't use semi auto most the time.....

Lugging that gear in and out of a ditch this size would kill ya! Plus the dirt and sand plays heck on them

Attachment: 1.1.bmp (352k)

Attachment: weldingpipe.bmp (276k)

Attachment: SDPipe.jpg (41k)

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By Stephan (***)

Date 09-25-2009 06:28

Hi pipehead!

Thanks a lot for sharing these pictures!

Hmmm... looks great and makes your decision understandable. You certainly have considered twice how to weld these lines optimally.

By the way, it's good to see that not everywhere a lack of qualified welders is observable, making it often necessary to use semi-automatic systems. ;-)

Best to you,
Stephan