wall thickness tolerances for ferritic seamless pipe for natural gas 1

[jaimeleiva]

Does anybody know what are the tolerances for wall thickness of ferritic seamless pipe use to transport natural gas? Somebody told me that it is -12.5% and +20.0%, is this correct?
Thank you,
Jaime L

 

[gr2vessels]

Hi Jaime,
Half is true, the first half. In the calculation of the available reinforcement, you deduct the 12.5% of "mill tolerance" and also deduct the corrosion allowance if applicable.
cheers,
gr2vessels

 

[davefitz]

The 12.5% is a standard B31 code allowance for extruded seamless pipe.However, modern extrusion methods in Japan and EU can provide much better wall tolerances than 12.5%.

In theory you can amke use of the better actual wall tolerance as follows: another code paragraph also allows the design pressure to be set based on measured wall thickness, if a truly all inclusive survey of the entire pipe is the basis of the as -recieved wall thickness.

 

[EdStainless]

The upper limit is technically set by total weight, and yes it could be as much as 20% if the stars lined up just right.

Get out the spec and read it.

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Plymouth Tube

 

[salmon2]

Yes, if you quote using API standard.

But you can ask for better tolerances and indeed the good mill can do it for you. But you have to work out with mill to find a reasonable price and min purchase volume.