Ovality in Line Pipe

guniting? this is the application of ccement or similar,correct?

lets see, 14mm= .55118", at .2759"/side hmmmmm

lots of variables. if all inspection methods agree then pre and post shipping can certainly be an issue.

I suspect your joining methods are now compromised. OUCH!

Sounds like the pipes are being crushed during transportation

This is caused by:

• chains or strapping being cinched down too hard on the truck.
• Pipes being stacked too high
• no protection of pipes

Preventative processes:

• Ship pipes with connecting rings already attached
• Use protective forms to separate pipes when shipping
• Regularly roll the pipes
• switch to spiral welded pipe
• restrict the height of stacking

Don't worry. A little bit of internal pressure and they will become circular again...

This kind of increased ovality could occur during transportation where the roads are uneven and the trailers are exposed to jerks. Repeated downward swings can cause the pipes (especially if they are 12 Meters standard lengths instead of the shorter 6 Meters) to gradually yield increasing the ovality.

Being gunited, it is likely that there are also cracks in the gunited surface to allow the yield. So it is also advisable to inspect the surface of the gunited pipes.

The API-5L spec allows for degrees of ovality commensurate with the diameter of the pipe itself. Ovality/Diameter gauges are used to check this during manufacturing and (in the field) at alignment for welding. The tolerance for the body of pipe greater than 36" dia is stated as +/- 1.00% for nonexpanded, and +1/4" -1/8" for cold-expanded pipe.

At the ends (critical for weld alignment) it is +3/32" -1/32" for the diameter, and +/- 1.00% for the out-of-roundness.

Your 40" line is permitted (by the 5L spec) to be 0.4" out of round. That which you state to be 10-12mm equates to .3937" (acceptable) and to .472" (unacceptable... and, most certainly, the 14mm, at .55" out-of-round, is also unacceptable.

Options to "junking-the-lot" exist. If it's already offshore on barges, preparing to lay (the cement-coating is referred-to as weight-coating, on subsea lines) , it will be a bit more complex to achieve tool-wise.

Will the welding be by automated machine, or 'skilled-hands'? What do the hands say, and, where on the globe is this being performed?

May your endeavors be blessed with success...!

Thank you all specially techno and kasharma for all your valuable inputs.

But questions comes to me here that considering size (48") and wall thinkness (19.6 mm) of pipes, is it really possible during transportation or staking this kinda really heavy pipes can get distorted in such way that increase its ovality out of tolerence ?

Thanks and regards.

Yes, out of roundness is actually more prevelant with the larger pipes. More weight is suspended over a larger distance and you get lever action on the left and right edges.

It is very common in the machining industry to have specs that address shipping issues clearly defined.

Lets say I have a customer (Intel, HP, LSI) who needs a corrosive gas manifold that uses 400' of 1/2" <5R_a tubing that I need to send out for some secondary operation. My outsourcing outfit must comply with my spec for shipping handling etc. and my spec does me no good if it does not cover my clients specs at a minimum.

It is VERY common to have quality and workability issues as a result of vague or assumed shipping specs.

I cannot tell how many times I have outsourced $300 processes/features and received a $3000 headache. Fortunately I have a solid leg to stand on (written spec) that the vendor agreed to meet (often unaware he agreed, or unwilling to admit) when he reviewed and signed the bid package.

I have found that more often than not the company simply did not understand the importance or did not review specs thoroughly prior to accepting, or that the guys in shipping were simply not aware of a special need vs. their SOP (stand. operating procedure)

(6:10pm)...apologies for my error this morning. In my haste to respond, I mis-read as 40" instead of 48"... (Abdel provided the correct tolerance; .48", not .40"... which, of course, means that your areas of 10-12mm deviation are "acceptable", tho the 14mm deviation is still just out-of-bounds).

I once asked about the carved-out wooden beams (curved to fit the pipes) that are used to separate sections of pipe during rail-car transport to-and-from the pipe coating facility nearby. When I asked (I thought rhetorically...!) if that keeps them from hammering each other out of shape (along with protecting the coating) I was told that they help to "minimize" the deformation caused during rail transit, but not eliminate it. The repetitious, relentless bouncing of tons of steel cannot be totally absorbed by the wood itself. The pipe does yield itself somewhat.

Best Regards ~

According to API 5L, Table 7. Tolerances for Diameter of Pipe Body, for 48" NPS, Seamless Pipe, the tolerance shall be ± 1% D (where D = Specified OD), i.e. the tolerance shall be ± 0.48" (12.19 mm).

And according to API 5L, Table 8. Tolerance for Diameter at Pipe Ends, the tolerance shall be 1% D, with the limitation of max. differential between min. and max. diameters (applies only to pipe D/t ≤ 75) is ≤ 0.625" (15.9 mm).

I have seen a lot of this during my years.

Any anti-bouyancy coating will cause this because of the added weight.

Heat affects this also.

Try rolling the pipes 90 degrees and re-measuring the next day, and than take the average for your ovality factor!

Could eliminate a lot of confusion and calculation!

The ovality is measured as a max & min for a pipe across 360 deg. along face of the pipe. The ovality may increase due to induction heating at the coating plant while applying the epoxy i.e. 3 Layered PE coating. It is for this very reason the ovality at the manufacturing end should not be exceeding 2-3 mm as per Det Norske Veritas specifications { refer DNV rules for Offhore Pipelines }.