When to Use Seamless and Welded Pipe 4

[SmallInfo]

Hi Experts,
I have to choose pipe welded or seamless for raw gas but it's for 10 to 15 years not more than that, its API 5L X42 fluid is corrosive, no high temperature and pressure. I am looking for any reference from any standard which tells when to use welded and seamless or at least some valid technical points to defend my selection.
Thanks in advance.

 

[dik]

Ed...
Can you elaborate on that a bit, or point me in the direction of some literature? This thread is not my type of work, but is very interesting. Thanks...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[EdStainless]

Since most of my last 30 years has been in SS and Ni alloys I'll speak from there.
These are only fusions welded, no ERW and there is no filler used.
So you have TIG, Plasma, Laser, EBeam, and variations/combinations of these.
Traditionally the worry has been hot cracking of welds which tend to be transverse and this has lead to the very common use of Eddy Current testing. ECT will easily detect transverse indications with high sensitivity.
However we know that all fatigues cracks will start at longitudinal indications. The only good way to detect these is using Ultrasonic testing.
This especially applies to tubing that has been cold drawn where draw scratches and other issues will all be longitudinal.
To put some scale to this when we make aerospace hydraulic tubing (welded and as-cold-drawn 21-6-9 SS) the UT uses notches that are 0.002" deep and 0.25" long, on both the ID and OD.
All of our seamless tubing was UTed.
And for highly fatigue sensitive alloys like Ti all tubing (welded or seamless) is UTed as well.
Start with a list. what is the weld method and what are the most likely weld defects?
What NDT methods are available (listed in applicable specs)? What will they detect and with what sensitivity?
Also consider the impact of HT. In steels with weld-only HT there are a ton of local HAZ issues to consider.

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P.E. Metallurgy, consulting work welcomed

 

[dik]

Thanks, Ed... much appreciated... I owe you a beer...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[r6155]

Seamless pipe is the best choice for forming operations involving coiling, bending, etc.

Regards

 

[SJones]

If the party responsible for purchasing the pipe is not operating a pipe mill appraisal scheme, and will simply go with a mill that is listed on the API Composite List, then it would sway the selection towards seamless even if it is more expensive. It will also aid inspection, should purchaser inspection be deployed, since there will not be any welding, and weld NDT, activity to monitor.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[0707]

I agree with you SJones, you merith my star!

 

[EdStainless]

r6155, not necessarily. The better diameter and wall uniformity of welded pipe often make it much easier to form.
You need align the usage and the product.
"you don't get what you expect, only what you inspect"
If you are not willing to send a specialist to the mill then you are agreeing to take the worst product that they might make.
Even with seamless there is HT, lab testing, and NDT that need to be done right.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed