Pipe questions - Induction Bends

[ElectricMech]

Can anyone answer any of the following questions:

Where I can find the specified ovality of a pipe? Is this something that is provided, from a table, or is there a rule of thumb?

In doing an induction bend calculation it asks for the set minimum wall thickness (%). This is different from the API positive and negative wall tolerances. Any idea what this is refering to?

Sizing plates, is there a table somewhere of standard plate sizes to choose from? If so can anyone direct me to it.

Thank you in advance!

 

[ytse]

Check PFI (Pipe Fabrication Institute) Standard ES-24. It provides all the standard tolerances for wall thining, ovality, etc for different types of pipe bending (including induction bending).

 

[BigInch]

You provide that number. It is the degree of misalignment YOU will allow.

Minimum wall thickness is the minimum wall thickness YOU can have and still safely contain the pressure according to your specific design code, pressure and material selection.

you'll find your pipe tables here,

http://www.pipingdesign.com

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[rconner]

I think "ovality" of manufactured steel pipes means different things to different folks/standards. I believe there is e.g. an ovality limit described in steel line pipe standard API 5L. This is apparently some different at least in formulation than the out-of-roundness or ovalization as defined by DNV codes. I guess multiple things could be considered in the development of such limits e.g. facilitation of fit up in welding operations etc.
Now, as far as absolute ovalization induced or allowable e.g. by thereafter reeling or in various fashions and to various extents beam etc. bending such pipes or pipe sections, I would think that could be another matter, that could be influenced by your specific fabrication procedures and/or application etc. (that could be what Mr. BigInch is getting to). There is at least a discussion of the different ovalization expressions as previously discussed as well as some specific reeling etc. effects in some offshore applications in the paper at

http://www.optical-metrology-centre.com/Downloads/Papers/Technip DOT 2003 Paper.pdf

(see e.g. page 4).

 

[BigInch]

The ovality (outside its possible wall thinning context) of the pipe is a value that is used primarily for these three things,

1. To minimize line-up problems on a tack and root weld when welding two joints together, in which case it only really need be specified for the pipe ends and the length between could be limited to some other value.

2. To predict the likely onset of collapse due to circumferential buckling from external pressure, most specifically applied by water pressure during offshore laying. Important because a small deviation from a perfectly circular section can reduce buckling resisting significantly from that of a section with a perfectly circular section.

3. Passage of a guaging pig (or any other tool) after construction to determine if there were any kinks or buckles that were missed by the visual inspection during laying or happened during the hydrotesting. For mechanical passage and to determine if the pipe section properties at any point might have been reduced to critical levels.

It could be considered for some design purpose to be in excess of the maximum permitted by the API pipe specs, in which case the maximum value allowed for such purpose should be supplied by the design engineer.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com