When to Use Seamless and Welded Pipe - Eng-Tips

LittleInch

Petroleum

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Mar 27,

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GB

What design code?

How corrosive?
With what?
Size and wt affect availability. Above about 16 to 20" seamless gets hard to find

This is more of a material selection issue and I don't know if any pipeline code which will tell you this. B31.3 doesn't like welded pipe for some reason and applies a factor on wall thickness

There is a lot of preferential engineering here and different companies have different views.

There should be little difference but you may need to look at the impact of the seam weld on corrosion issues.

If you have sour service (H2S) then seamless is definitely preferred, which is a material selection issue under the NACE standards.

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SmallInfo

Petroleum

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Oct 30,

104

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PK

LittleInch,
Its H2S rich
b31.8
8" size
Client will ask why I am selecting seamless or welded.
Thanks for reply Upvote 0 Downvote

LittleInch

Petroleum

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Mar 27,

23,229

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GB

You need to ask a materials engineer, but I'm pretty sure for sour service you need seamless if possible and 8" the cost is about the same.

It's all about the hardness of the weld. Also look in your sour service specification.

Design wise in 31.8 it makes no difference and they won't guide you as it is not something B31.8 does.

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TiCl4

Chemical

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CA

A general rule for corrosive services is that seamless piping is preferred - ERW pipe tends to be attacked along the pipe-weld bondline at a higher corrosion rate than the base material. My impression (not fact!) is that mill tolerances for wall thickness are either higher for seamless pipe over ERW pipe or that they are harder to get within tolerance (more expensive). So if you need to do branch reinforcement calculations for larger diameters or higher T&P, the mill tolerance becomes important.

Piping codes don't generally tell you what pipe to use in a given application; there are generally too many factors and special cases, so they leave the application up to the user.
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EdStainless

Materials

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Waukesha WI USA

Seamless will have much more variation in wall than welded.
Seamless also usually has a rougher ID surface.
In ERW steel pipe there can be selective HAZ corrosion attack because it isn't full body heat treated after welding.

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weldstan

Materials

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For your application choose seamless due to answers provided above. Due to our global supply chain and the vast differences in ERW welding methods from mill to mill and quality thereof, a greater chance of failure is incurred using ERW. ERW pipe can be made with excellent properties but you really have to know the mill's capabilities. Upvote 0 Downvote

MJCronin

Mechanical

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Apr 9,

5,102

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US

My two cents ...
[ul]
[li]No piping code or standard will tell you when to use more expensive seamless piping and when not to[/li]
[/ul]
[ul]
[li] Are you selecting schedule 80 pipe for this corrosive service ? Having a thicker wall will make the piping last longer[/li]
[/ul]

[ul]
[li]Some B31 series piping codes have a higher allowable stress for seamless piping ..Seamless pipe can withstand 10-20% more working pressure than welded ones of the same material grade and size.. On what basis was your pipe wall thickness calculated ?[/li]

[/ul]


MJCronin
Sr. Process Engineer Upvote 0 Downvote

TiCl4

Chemical

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May 1,

646

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CA

MJCronin,

When would the MAWP of the piping become the deciding factor for a piping system's thickness at low temperature and pressure? In my mind, required thickness is often very low at low T&P, and other factors like maximum unsupported span and extra thickness for corrosion allowance tend to dominate. Typically pressure is also limited by the flanges or connectors rather than piping, is it not?

I'm not challenging you here, but rather curious as to where you've seen or heard of the extra MAWP of the seamless pipe being important in the selection of ERW vs seamless. Upvote 0 Downvote

SmallInfo

Petroleum

Joined

Oct 30,

104

Location

PK

Littleinch, TiCI4, Edstainless, Weldstan, MJCronin
Thank you so much for your valuable time and information you shared, now its clear to me.
Thanks again you all Upvote 0 Downvote

EdStainless

Materials

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May 20,

16,417

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Waukesha WI USA

At thicker walls the seamless premium is not very much more expensive.
Many ASME codes do derate welded tube by 15% for no reason other than it was welded.
The seamless tube will always be heavier and the thinnest spot will be thinner than with welded tube.
The greater wall variation is just a fact of life.


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r

Mechanical

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AR

For 10-15 years choose the cheapest.

Regards Upvote 0 Downvote

Petroleum

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PT

Each great project company in oil industry have its own basic engineering specs based on standaed codes, I am afraid you won´t recieve the wright answer here.

REGARDS Upvote 0 Downvote

Daren Samy

Mechanical

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Oct 6,

59

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PK

Use seamless pipe. ERW pipe is not recommended in severe conditions. Welded point is weak points and it is at risk of failure

Daren! Upvote 0 Downvote

dik

Structural

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CA

... but informative, nonetheless.

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

-Dik
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Petroleum

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PT

Seamless steel pipe is better than welded pipe. Seamless steel pipe is limited in larged diameters up to 24". Upvote 0 Downvote

r

Mechanical

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Jan 12,

3,065

Location

AR

@
You are wrong.
See SA-106
1.1 This specifcation covers seamless carbon steel pipe
for high-temperature service (Note 1) in NPS 1/8 to NPS 48
[DN 6 to DN ] (Note 2) inclusive, with nominal (aver
age) wall thickness as given in ASME B36.10M

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Petroleum

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Jun 25,

3,468

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PT

r
you're right, I was speaking generally. But the use of welded pipe and seamless pipe depends on the intended service. If it is going to be used for a lethal dangerous, high pressure or corrosive service I would use seamless pipe, if it is going to be used in an enoquo service I would use the cheapest welded pipe. Upvote 0 Downvote

EdStainless

Materials

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May 20,

16,417

Location

Waukesha WI USA

Seamless pipe isn't better than welded, it just has different types of defects in it.
With welded you get very uniform surface finish inside and out along with very uniform wall thickness.
The type of welding will dictate the nature of weld imperfections that you should be testing for, and the HT method (local to weld or full body) will influence the final properties of the pipe.
Seamless pipe will always have very significant wall thickness variation (commonly over +/-10% in each length) and the ID surfaces can have significant variation in surface.
Tears and cracks on the ID surface are not uncommon in seamless product.
Seamless over ~24" OD is usually forged hollows made in short lengths.

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