Visual Examination of Longitudinal welds in pipelines.

Hi Andrei,

In your avatar it looks like you are standing in front of my office!

Anyway, I think general practice is to shift spools so that longitudinal welds do not line up, but I don't have a reference... sorry.

Steve S

Agree. To the best of my knowledge (do not have a copy available) API 1104 does not stipulate any offset of the longitudinal welds. It is however quite normal to restrict the position of the longitudinal weld to the top 1/3 of the pipe diameter and to offset the longitudinal welds on abutting pipes by around 1/2 the diameter.

Thanks Sridhar,
May be you can get some reference links in Standard, Books, ...

As I know as per Russian standards from GAZPROM, the circ.distance between longitudinal welds on pipeline should be not less than 100mm (it's not depend from pipe diameter).

Many times pipe connections are provided at 45 deg. It means the same will fall on seam welds. Is it OK?

Please add to your good answer "in buried pipeline the seam must be welded in the line of top quarter of pipe circumference". This is just to convene detection of leak or burst. The blow of burst clear open the trench and small leakage would wet the backfill quickly. In preparation of vessels or above ground pipping this condition is not necessary.

Yes AbdulWasay,

The same meaning is already inclusive because the under ground pipeline means buried pipeline.

There is a much more important reason for keeping the welded seem at the top. The point of greatest corrosion tends to be along the bottom of the pipe due to "under debry" corrosion, so keep the weld away from it.

Hi Andrei, When setting up for a butt weld on seamed pipe if possible you should have the seams minimum 90 degrees apart also grind seam flush approx 25mm or 1" from end of pipe or when ndt (radiography) may pick up the raised seam at the butt weld when you flush the weld off you also remove any stress raisers.

Hope this is of use regards, John.

Hi Andrei, I think you will find the info you require in ASME B31.3 AND B31.4

tHERE ARE DIFFERENT STANDARDS FOR DIFFERENT CONTRIES AND EVEN COMPANY STANDARDS IE BP. SHELL ETC

B31.3 FOR PROCESS PIPING

B31.4 TRANSPORTATION OF PIPELINES.

REGARDS.JOHN.

Thanks John,

I checked twice the standards you recommended (ASME B31.3 AND B31.4) but I found no any links with longitudinal welds.

By the way THANKING you and thanks for all for your recommendations.

Andrei.

AWS D1.1 Cl. 5.22.3.1 :

Longitudinal weld seams of adjoining sections shall be staggered a minimum of
90°, unless closer spacing is agreed upon by the Owner and fabricator.

The reason behind this offset practice is to minimize the accumulation of defects and the heat input at the intersection of welds. ( At one cross intersection you have 4 ways , and at a tee intersection you have only 3 ways ).

Therefore the offset has to be more than two times the heat affected zone for the material that is welded ( those 100mm from GAZPROM works fine for that, but also a specified angle of rotation - 90 degrees or similar ).

In addition to this , in order to give a better and regular appearance for long lines, you may impose an angle of rotation.

(No specification up to my knowledge.)

You are right.

But 100mm in GAZPROM RP document is a minimum size between Long.welds.
If more, then welding pipe section will not pass examination.

Rotation on 45 - 90 degrees is ok, but sometimes it's difficult.

Thanks.

Hi Andrei, I have fitted several prefabricated seamless spools s/s with branches flg's etc thats been ndt hydrotested ect but if you have spools coming from different fabrication shops when they arrive on site and its a tie in spool the client normally will give a dispensation and log that the seams line up but due to cost ect basically let it go.

Hope this is of use to you.

Regards, John.