Pipeline Bends - Minimum Bending Radius

[Abuza]

Which is the limiting minimum elastic bending radius for Pipeline bends( for Gas Flow Lines):

- The one stated in ASME B31.8 section 841.231 OR

- The one given by equation : R(min) = (3EI)/(2ZS).
where E = Modulus of Elasticity
I = Cross sectional moment of Inertia
Z = Section Modulus
S = Allowable Stress

- Or any other consideration for this.

 

[corrosionman]

Abuza, I am probably off line with my reply, but, if you are designing or building a pipeline then the bends will be what you can buy off the shelf for welding into your system.
You have the choice of what are called standard elbows or swept bends. I forget the respective ratios but any piping supply company will know. Regards DW

 

[DrillerNic]

When I was building pipelines, the typical limits were:

For elastic bends 50D

For plastic bends (with a bending machine with an internal mandrel) 15D

For hot induction bends (i.e. manufacured by a mill) 5D. This latter limit was forced by the pig manufacturers, as the minimum radius an typoical intelligent pag can go around is 5D. if you're not going to use intellignet pigs, you might be able to reduce the minimum radius futher.

 

[MTPipeliner]

A word of caution, that you are probably already aware of.

Some pipelines are required to be constructed to allow for the use of smart pigs by DOT code.