Cold bending of straight pipe

[rajenmenon13]

Is there a formulation, where by we can calculate as to max bending degree of a 20 inch OS diameter pipe of standard 12 meter length and how it can be corelated practically.
Menon

 

[dhengr]

Rajenmenon13:
This type of work requires special tooling and bending equipment and considerable experience, not just some formulation. It is highly dependent on the strength of the pipe steel and the wall thickness vs. the pipe dia., etc. I would talk to a local fabricator who does this type of work regularly. Google pipe and structural shape bending, there are a number of companies doing this kind of work.

 

[LittleInch]

Menon,

Pipeline bending is typically done to an inner radius of either 40D for a field bend or 3D or 5D for a hot formed bend.

I once did 10D for a cold bend, but it needed special treatment and sand packing to stop it wrinkling.

For a pipe of 12m long, leave at least 1m at each end. Then your angle is simply an arc of radius 40 x D, 10m long.

Circumference of your arc is 40 x d(in m)x 2 x Pi. Angle is ( 10 / circumference ) x 360.

Is this what you meant??

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[racookpe1978]

The length at each end is set by the distance between the center roller and the two fixed rollers on the machine in question, plus a margin to start/stop the pipe.

FIRST and before ANYTHING ELSE find some one in your area or the fabrication area who already has the machining, the cranes and layout tables for 20 inch pipe, and the transportation to get the pipe to and from his shop to where ever you need the bent pipe. That company (for a twenty inch pipe capacity) has invested many tens of thousands in a machine not often used. Expect to pay a lot.

THEN, ask that company how far they can bend successfully and reliably 9or with what number of failures to successes for each bend diameter. Far, far more than steel welding, pipe bending is an art that doesn't always work. You will find the roller and foreman far more important than the company salesman. Do NOT believe just thumbrules - skilled rollers will be able to break thumbs and thumbrules.

Specify a bad setup, you WILL pay for the many failures between each successful bend. Set up a good, easy, well-practiced bend on a table and machine capable of that work, and you will get good bends all day every day.

 

[saplanti]

I would not try cold bending for this diameter of pipe whatever the thickness (which you did not mentioned) is. Ask for hot bend instead.
The forces generated on the rollers are going to be very large if you want to end up with a proper bend and straights due to the short distances to be used between rollers depending on the bending radius you are after. In case you use large distances between rollers although the bending radius require short distances you will not get the proper bending shape, the pipe will bow immediately from the rollers. So the shape and strain control will be difficult. The spring effect is another to be considered.

You can find simplistic equation for beam bending curvature and stresses created:

http://www.freestudy.co.uk/statics/beams/beam tut1.pdf‎

 

[saplanti]

Here some others:

http://www.eng.uah.edu/~wallace/mae466/DOC/bas_str.pdf‎

http://www.personal.psu.edu/juc47/Course/EMET222/BDupenBook.pdf‎

Just to remind you the calculations are here and above are valid in elastic range.

For plasticity you may consult Roark's Stress and Strain Handbook.

 

[saplanti]

I have found an article about cold bending that you can reach from the link below:

http://www.google.com.au/url?sa=t&r...3S3SHs-Boxbp_Xa-l2ABvug&bvm=bv.61190604,d.dGI

However this is for the I beams, but will give you the in-light of cold bending.

 

[saplanti]

This is a good one to read:
(Section slenderness limits of very high strength circular steel tubes in bending)

http://www.google.com.au/url?sa=t&r...eb&cd=75&cad=rja&ved=0CD8QFjAEOEY&url=http://

http://www.researchgate.net/publica...Q9Yf1LqCdtetaIoXL6K-ZTw&bvm=bv.61190604,d.dGI

 

[tbuelna]

When you form a hollow section shape (like a tube or pipe) over a circular mandrel, the outer section of the pipe will be forced to stretch. With a large diameter pipe/tube, the force required to stretch the outer wall during bending can cause the pipe/tube cross section to flatten if the inside is unsupported. If the pipe/tube wall is thin, the inside wall section can also buckle.

Per the specific question posed in the OP, the included bend angle possible with a 20" OS dia pipe would depend on the pipe wall thickness, the CL bend radius required, how much thinning is acceptable in the outer pipe wall at the bend, and how much deformation is acceptable in the inner pipe cross section at the bend.

 

[3DDave]

If you fill the pipe with lead, it will prevent buckling while bending.

It's going to take a lot of lead.

 

[BigInch]

Just another day's work,

https://www.google.ae/search?q=pipe...9VUqK_sBu73gKAI&ved=0CEQQsAQ&biw=1030&bih=640

I hate Windowz 8!!!!

 

[berkshire]

If your code will allow it, an alternate, is the hollowed segmented bend, ( Full lobster back ). They are more expensive to produce, but require less capital outlay for forming machinery. You only require a couple of skilled guys with a power hammer or drop forging machine.
The biggest problem these days may be finding the men not the machinery.
B.E.

You are judged not by what you know, but by what you can do.