Bending Electric Fusion Welded Pipe

[gowvu2008]

Should I avoid bending EFW pipe and strictly use fittings? If it's OK to bend EFW pipe, what precautions should be taken versus seamless pipe? Does it matter if the weld joint is along the side of the bend or on the inside/outside of the bend? Any help and experience with this is greatly appreciated.

 

[SJones]

Induction bending or cold bending?

Steve Jones
Materials & Corrosion Engineer

http://www.oilandgaspeople.com/cv/11499664

http://www.linkedin.com/pub/8/83b/b04

 

[gowvu2008]

Cold Bending

 

[BigInch]

Cold bending is not an option for fittings, unless you want 100D fittings

"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
"Being GREEN isn't easy." Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.liv

 

[gowvu2008]

I'm only interested in cold bending the pipe. I only mentioned fittings because it is an alternative to bending.

 

[moltenmetal]

Presuming this is carbon- or stainless steel welded seam pipe or tubing of an ASTM grade suitable for use in pressure piping, cold bending to replace elbows is common practice. Bends using proper bending mandrels of reasonable bend radius can be done irrespective of weld seam orientation. Others may be able to comment on differences between EFW and ERW or to provide advice on an optimal weld seam orientation, but when multiple bends are done you will end up with the weld seam in the wrong orientation at some point anyway.

 

[BigInch]

Keep the seams on the neutral axis (or as near as possible thereto)!

"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
"Being GREEN isn't easy." Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.liv

 

[corem16]

Gowvu2008,

You can check ASME B31.3 - chapter V - parag. 332 (Bending and Forming).
As BigInch said you should avoid put the longitudinal weld joint in the intrados or extrados of the bend.

 

[sjrfc2]

There is a bending spec for the Navy (Mil-Std-1627) that resticts the weld of a seam welded pipe from the introdos, extrados and neutral axis. Preferred location is shown at a position between the extrados and neutral axis.

The intrados and extrados are going to be max plastic strain but on either side of neutral axis (NA) is going to be max residual stress since the NA doesn't change length. As you move farther away from the NA the material yields and this will limit residual stress after the pipe is released from the bend machine. The areas of high residual stresses will be more susceptiple to corrosion and that might have been the reason to avoid the NA.

Increased ovality will also drive hoop stresses up and it could have been a reason that the NA was also identified as a location to avoid with the weld seam on a bend.