pipe wall thinning due to bending

[pipe15]

The B31.1 code gives 'recommended' values to use for thinning when bending pipe in section 102.4.5. From what I hear, these values are very conservative. (8% for 5D and 25% for 3D) What are reasonable values from experience? I realize that the thinning is dependent on method, size, and wall thickness. What could I expect with a 30" pipe with 1" wall, given heat induction bending? Any other values based on experience for other sizes would also be appreciated.

thanks
Mark

 

[metengr]

From what I hear, these values are very conservative. (8% for 5D and 25% for 3D) What are reasonable values from experience?

Sounds to me like someone has already made a decision irrespective of the Piping Code recommendation (which by the way is based on practical experience).

 

[BigInch]

Best stick to the code.... like glue.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[StoneCold]

You could bend the pipe and then measure it. If you are wrong about how conservative the codes are then you will have to derate your pipe. You will also be taking on considerable liability for the design.

Regards
StoneCold

 

[BigInch]

Or the inspector will simply make you cut it out and do it again until you get it right.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[NozzleTwister]

The pipe bending shops can certainly tell you what thinning they can guarantee.

If you have a lot of bends, ask them to demonstrate that they can do what they say they can before you place a big order.

Check the wall on each bend and reject any that are too thin.


NozzleTwister
Houston, Texas

 

[JohnBreen]

You might want to look at PFI Standard ES-24.

 

[davefitz]

as I recall, Mannesman Vallourec publishes curves of bending r/d ratios vs extrados wall thinning for some pipe materials.

Also, some EU design codes explicitly allow for thinning at the extrados toa min wall less than the standard staight pipe minwall , due to the effects of work hardening and the fact that the theoretical stength of such a bend ( which has 2 radii of curvature- so called toroidal equations) is tronger tahn the original cylinder. But I thibnk the US piping codes to not allow for this for pipiong in the workspace.

 

[CLINDU]

There is std called PFI standard ES-24 which is a manufactuer std. You can find the anwser there. Depend on how you bend it and the radius of bend, the thining can be big diferent. For furnae bending, from 3D to 6D, the thining can be 25% to 6%.

Clinddu