Maximum Field Bend Radius for Pipeline

Dear Tornado,

I appreciate your good answer. Bend radius with min. 5D is required for those pipelines use bigs for cleaning, inspection, 2-fluids/patches separation, ... etc. to facilitate crossing of pigs, and no way to use standard elbows (Long Radius 1.5D nor Short Radius 1D) in that type of pipelines.

So, in pipelines used bigs, the min. bend radius is 5D and max. bend radius is infinity (straight pipe). And all codes and standards permits fabrication and installation of those bends.

As per ASME B31.4 (Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids)

404.2.2 Field Bends. Field bends are cold bends, generally made in the field during construction, to allow the pipe to conform to the contour of the ditch. Field bends include vertical bends (sags and overbends), horizontal bends to accommodate changes in direction, and combination bends.

Bends shall be free from buckling, cracks, or other evidence of mechanical damage. Ripples or wrinkles meeting the requirements of para. 451.6.2.8 are acceptable. Field bends shall meet the requirements of para. 434.7.1.

The minimum radius of field cold bends, except as noted in the next two paragraphs, shall be as follows:

Maximum bend radius of a buried pipe, on Earth, would be 3950.5 miles.

(But not good enough to make me go back and vote myself OT.)

There is no OT when pursuing of the truth.

And then too, it depends on how deep you bury it....

1.5 meters is specified.

I hereby adjust your excellent answer to 3950.4992 miles. (Or something like that--it's too late for arithmetic.)

I'll drink to that. Again.

If I had a brain I'd go to bed.

Do you suppose SUTHASINEE has a clue?

Even the fun replies actually convey some information, albeit a bit abstract. But I don't think Post 1 was too bad.

It goes downhill after post #1, for sure.

Are there formulars to calculate "Minimum field bend radius for pipeline" as above mention condition?

Thanks and regards,

SUTHASINEE

I don't think there is any one formula for this; it depends on the bending method and the pipe material, whether heat is allowed, etc. For nominal pipe diameter D, forged fittings are made of various center-line radii: "short radius" r = D, "long radius" r = 1.5D; "3r" radius = 3D. Induction-heated bends can be fairly small radius; torch-heated and hydraulically formed bends maybe 5D or so, etc. As mentioned before, local Codes and contract specifications may dictate the bend radius. Cold bends formed hydraulically or around a mandrel will spring back about 2-3°, depending on material; so they must be "overbent" accordingly.

Try not to bend 6in pipe. Try to fit factory-made elbows into it.

Piping grade A53-A is (or was) made more-or-less specifically for close-radius bending, as used in serpentine "coils"; there is (was) a special "flattening test" dictating how ovoid the pipe can become around 180° bends. If any coatings are involved, they are applied after bending.

(Maybe I am describing a lost art/technology from the "old days", sort of like how oxyacetylene butt-weld joints have largely been supplanted by knobby socket-weld fittings in small sizes. Yecch.)

Pity St Gobain shut down their UK pipe spinning plants. Our speciality was "bent" ductile iron pipe. They weren't supposed to be bent but, well, things went wrong at times.

I wonder what it would do under its own weight?

Proably fall off the edge of the earth!!!!!

My best guess is the following... (assuming ASME B31.8 applies)

Elastic bends: 50 x pipe diameter
Plastic bends: formed with a pipe bender with an internal mandrel: 15 x pipe diameter