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Using erw pipes to make cs elbows
2

Using erw pipes to make cs elbows

Using erw pipes to make cs elbows

(OP)
can carbon steel erw pipes (and not seamless) be used to make 90degrees LR elbows using cold pressing (not heat induction)?

RE: Using erw pipes to make cs elbows

Usually.  Put the longitudinal seam at the 9 O'clock, or 3 O'clock position and bend vertically, from 12 O'clock to 6.  The radius may need to be rather long, depending on pipe diameter and the wall thickness of your pipe, and you may need an internal mandral to prevent excessive ovaling on tight bends.

In this picture the seam would go along the top surface line, in a line connecting along the brightest light reflections.

What would you be doing, if you knew that you could not fail?

RE: Using erw pipes to make cs elbows

Yes but be careful.
ASME B31.3 has a limit for outer fibre elongation for impact tested materials, and that might limit how tight your cold bend radius can be (332.4.2 (b)).  Further, the same Code also states that if you are making elbows out of bent pipe, you must establish your pressure rating and thickness making use of the (sometimes called) Lorenz factors (304.2.1).  

RE: Using erw pipes to make cs elbows

I guess I should have asked what Code applies...I apologize if my assumption was incorrect.

RE: Using erw pipes to make cs elbows

Yes.  Most all the codes have some limitations on this.  B1.4 & 8 have rather large limits on radaii, 30 D or so.  Then again, in US onshore gathering systems, no code actually applies!!!

What would you be doing, if you knew that you could not fail?

RE: Using erw pipes to make cs elbows

(OP)
Thank you BigInch and Snorgy,
the code is ASME b16.9,elbows WPB234, 1.5D & 1D, 90degrees. SCH20&40 from 1/2" to 12"
An internal mandral will be used.
Can you tell me if it is possible to make those elbows without breaking the seam during the cold pressing?
Thanks

RE: Using erw pipes to make cs elbows

From what I know, well let me say rather, what I don't know, I don't believe that you can do it cold.

What would you be doing, if you knew that you could not fail?

RE: Using erw pipes to make cs elbows

The other thing that might factor into it is whether or not you have to meet a tolerance on wrinkling (intrados) and ovality after bending.  Most shops that I know in my area would not undertake to cold bend pipe tighter than 10-D if they had to meet specifications limiting these effects.

Orienting the long seam along the neutral axis of the bend (per BigInch) should mitigate most of the problems associated with failing at the seam - again, assuming that your wrinkling and ovality are within certain limits.

It might be prudent to call for before-and-after hardness tests on the bend extrados to attempt to quantify any strain hardening effects.

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