pipeline slope 2

[fabien2121]

Dear expert;

It's possible and acceptable to make slope (3 degree & length 20 m ) in trench of pipeline instead of cold bend .

Pipe diameter is 12 inches.

Thanks in advance

 

[1503-44]

Yes. That 3deg you speak of is the maximum alignment change that can be made at a joint without using a cold or hot bend.

Be careful with wall matchup.

 

[LittleInch]

Do you mean 3 degree at a joint or 3 degrees over a 20m length as an elastic bend?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

Good question.

 

[fabien2121]

3 degrees over a 20m length

 

[goutam_freelance]

It appears that you want to introduce an angular offset in the pipeline. Similar to Miter bends we compare the allowable angle (B31.1).

So if you have sch 40 pipe then allowable angle is 2.31 degrees to consider the welds as normal girth weld.
So in effect the joint becomes non standard and stress intensification factors etc. needs to be established based on relevant code.
So it is better to reduce the offset angle to be within code limit or break the angle offset in 2 stages of approx. 1.5 degrees each.


Engineers, think what we have done to the environment !

https://www.linkedin.com/in/goutam-das-59743b30/

 

[fabien2121]

we have sch 30 pipe (8.38 mm ).

 

[goutam_freelance]

So the allowable angle is 2.07 degrees.

Engineers, think what we have done to the environment !

https://www.linkedin.com/in/goutam-das-59743b30/

 

[fabien2121]

the Miter bend or angle offset is acceptable in pipeline ?

 

[goutam_freelance]

Miter bends with angle offsets are acceptable as per B31.1. But in case the angles are above the value given by the above formula the SIF, flexibility factor etc. are to be calculated as per Appendix D but only 90 deg Miter bend values are given. So if the angle is more than 2.07 deg and the bend angle is other than 90 deg then SIF etc. needs to be calculated based on other clauses as per code.
But if angle is less than 2.07 deg then it is regarded as normal girth weld and no special treatment is necessary.

Engineers, think what we have done to the environment !

https://www.linkedin.com/in/goutam-das-59743b30/

 

[1503-44]

Code requirements vary. You must note the provisions in YOUR design code.

https://www.eng-tips.com/viewthread.cfm?qid=477541

 

[LittleInch]

I must admit I had never seen that equation, but then I don't use B 31.1 very often.

B 31.4 has a simple limit of 3 degrees which is the max before it becomes a miter or mitre joint.

However 3 degrees over 20m with a 12" (300 ND) pipe is an elastic bend of just over 1000D.

3 degrees is 1/120 of a circle. Therefore circumference of the circle is 120 x 20 = 2400m. Radius of the circle is = (circ/ PI) / 2.

I am pretty sure this won't exceed any stress limits providing the curve / bend is smooth.

At 1000D or more it will simply lie in the trench bottom.

If you think you can accurately cut a 2 degree slope on a 12" pipe then I think you're in the wrong game.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.