Cold Bend vs Induction Bend 4

[Tuga29]

Hi, we were asked to replace some cold bend items for induction bend in the construction of a pipeline built in accordance with ASME B31.4.
What can you say to me about this issue? They say that will be easy for them to use induction bend instead of the cold bends.

 

[DVWE]

What size of pipe, material type, and size of bends?

 

[Tuga29]

From 4" to 18".
From 30D to 40D.
API 5L Gr B.

Thanks

 

[DVWE]

Am I reading your post correctly? 30D and 40D bends, not 3D and 4D bends?

Hardly any arc to these bends if 30 and 40 is correct.

 

[Tuga29]

From the design phase we have a list of cold bends and induction bends for the pipeline construction. Cold bends for 30/40D and induction bends for 4/6D mor or less. Now they want to change all the cold bend for induction.
ASME B31.4 just talks about cold bend and give minimum values for that.

 

[DVWE]

The only reason that I can think of is that they don't have the capabilities to cold bend the larger diameters...

 

[Tuga29]

They say that it's because of assembly issues, they don't have much space to the four pipelines... and using the induction bend they will have more space.
But is there any problem with this substitution?

 

[DVWE]

I don't believe that there is any problem with this substitution, as long as they meet the provisions of B31.4 and B16.49. Additionally, if you are having your vendor already do some induction bending, consider mirroring those requirements for induction bending qualification if they substitute for cold bends.

However, I would really question their ability to do such large bends on an induction bending machine. Maximum radius on small machines is roughly 60", mid-range machines is 175", and approximately 400" on larger machines.

 

[Tuga29]

Thanks for your answers DVWE.

 

[BigInch]

No problem with the substitution of hot bends for cold bends. They can be made to smaller radaii, hence will fit into narrow right of ways where insufficient space for the larger 40D bemds should have been made. Problem is that they are a special order item and can require long lead times, quality control, shipping, handling and placement and if damaged during shipping or handling, or during installation may delay things even more. Other advantage is that no pipe bending machine is needed. They are especially good for lazy contractors in that they usually also try to do over and underbends with natural gravity sags, which actually increase stresses in the line, as they don't have a bending maching available anywhere for making vertical bends either.

 

[canadapipe]

I don't see any issue with the substitution either. As BigInch says this should help the contractor keep a narrower RoW and may reduce your workspaces. The one thing you should look into though is the bend radaii, if you have four lines in one ditch and want to keep the pipeline separation equal or close to equal this may be hard as the bend radaii will change based on whether the line is on the inside or outside of the deflection angle. I just completed a twin line project and we ended up splitting the difference in our bend radaii but with 4 lines the separation requirements / consistency issues are magnified significantly.

 

[Tuga29]

@BigInch Just to clarify, they want to replace the cold bends for hot bends.

 

[LittleInch]

I agree wit BI. Induction or "Hot" bends usually cost substantially more, but will fit in the ROW easier. So long as they are not trying to charge you for this change then there should be no issue.

You haven't clearly stated what radius the induction bends will now be (Usually 5D) and what range of angles are they talking about.

It's a little surprising that this wasn't defined or worked out during the design and issue of the alignment sheets, but there's quite a lot missing in this story...

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

 

[BigInch]

No problem ... either wa

http://www.eng-tips.com/viewthread.cfm?qid=412588y.

canadapipe
The arcs of parallel pipes do not need to have the same turning centerpoint, therefore the radaii of each line's bend could be kept equal and induction bend geometries kept the same, simply by using different centerpoints for each pipe line. Parallel pipelines are not like rails on train tracks. I would much prefer to use unique centerpoints and have equal geometry for all bends (induction or not).

 

[Tuga29]

They will not charge us for anything and they still didn't show us the new radius or the range of angles. For me it was strange because they show us a list of cold bends and a list of hot bends in the project of the pipeline. Then they told that they want to change the cold bends for hot bends because of assembly space. I ask them if they will obvious change de radius and they say no.... they said everything will remain the same, just replace the cold bends for hot bends. Something strange is going on here...

 

[BigInch]

No bending machine.