Maximum Cold Bend Angle

maximum bend angle = 180 degre

an application in my industry calls for 90 degree bend of 1" sch.80 pipe &

as we know a steel pipe can be bent for 90 degree,but wht is the minimum radius need to be maintained at the bend and why is it so, is there any stand or formula govening that minimum radius at bend??

an application in my industry calls for 90 degree bend of 1" sch.80 pipe & as we know a steel pipe can be bent for 90 degree,but wht is the minimum radius need to be maintained at the bend and why is it so, is there any stand or formula govening that minimum radius at bend??

Cold bends are normally within 13 Deg. and 16 Deg.

What I want to know is whether there is a relationship between minimum Elastic bend Radius and the angle (angle after which a pipe can no longer be bent using cold bending method, but Hot Induction Bending).

Minimum Elastic bend Radius is given by R=ED/2S_a

Where E =Youngs modulus of Elasticity

D = Diameter of pipe

S_a = Longitudinal Stress allowed for bending

It is a lot more involved than that and your question doesn't include sufficient information to provide more than general answers.

Whether or not the pipe can be bent to the desired radius (or angle) depends on the material, diameter, wall thickness, and whether or not some material (dry sand or other temporary filling material) is used to prevent collapse or flattening. When pipe or tube is bent, the outer wall is stretched and the inner compressed and as a result of those opposite and unequal stresses, the pipe or tube tends to flatten or collapse regardless of whether it is done cold or hot.

The safe minimum radius for a given diameter, material, and method of bending depends primarily on the pipe wall thickness. As a general rule, standard weight wrought iron or steel pipe can readily be bent to a radius equal to 3.5 - 4 times the nominal pipe diameter. However, that minimum will vary depending upon the bending method employed and the pipe wall thickness.

A general rule for finding the length of pipe section in the bend is to multiply the radius of the bend by the included angle then multiply that product by the constant 0.01745. The result is the length of the curved section.

Thanks So much for your contribution.

The Pipe is a 36" pipe, Wall thickness is 12.7mm.

In some previous projects that I participated in, we have always adopted 15 Deg. and below as Field bends or Natural bends and above 15 Deg. we have always recommended Hot Induction bends (3D or 5D, as the case may be).

I have never known the basis for this choice of angles. I have always tried to find answers, but I've never gotten the right sources of information. If I can even have recommendation of a book or any of the international standards that give a good explanation (Elastic Bend Radius, Field Bend angles, Induction Bends, etc) I'll appreciate it.

But at the moment, this is my dilema:

I have already calculated the Minimum Elastic Bend radius and got 2160m (which is about 60D). So what I really want to know is how to determine the maximum angle for which field (cold) bends is no more recommended for this pipeline (is it 13 Deg. or 14 or 15 and why).

Some of the pipeline Data includes:

Operating Temperature = 50 Deg.C

Ambient/Installation Temp. = 25 Deg.C

Design Pressure = 1450 psig

Steel Class = API 5L X65

SMYS = 4.48E+08 N/m²

Modulus of Elasticity E = 2.01E+11 N/m²

Coeff. of Linear expansivity e = 1.17E-05 /deg.C

Thanks so much in anticipation.

Hi

I am presently Involved in the design for 10", A105, Seamless Sch 160 cross country pipeline. The Pipeline is routed parrallel to an existing road. At one stretch the road takes a bend whoose bending raidous is around 705 M and the included angle is 16.68deg.

In terms of Pipe line diameter the bend radious is around 277D. Can anyone help me whether this bend can be negotiated with natural elastic bend while laying itself without requiring any plastic cold bening. Is there any calc to justify the design?

Thanks in advance

regards,

Sanjai.N

Hi

From the Pipeline Rules of Thumb Handbook, The pipe can be considered as Cantileaver Beam with end load - which is possibly the worst loading sceanarieo - and arrived at the Minimum Elastic Cold bend radious allowed with in the code allowable stress. This is the bend radious the pipe can naturally take without entering in to the plastic state.

R= 3EI / (2ZSa)

R= Min. Bend Radius-----------------------------in

E= Modulus of elasticity 29x10^6 ----------------lb/in^2

I = Moment of Inertia = 0.0491(D^4 - d^4) ------ in^4

Z = Section modulus = 0.0982(D^4 - d^4) / D ---in^3

Sa= Allowable stress in PSI as per code. Yield stress factor F=0.5 for Gasline Type C consturction as per ANSI B31.8 (stringent) or Yield stress factor F=0.72 for liquid transportation as per ANSI B31.4 can be used to arrive Allowable stress.

Hi! Iam doing the Bend calculation for the Onshore under ground pipeline project.

My Question is Wat factor i want to consider to calculate the bend angle or arc Length for Elastic bend, 5D hot Induction Bend & Field Cold bend? What data i want to refer to calculate for this? Is there any formula or we have to calculate based on the thumb rule? iam fresh in this area. please advise.

Hi! Iam doing the Bend calculation for the Onshore under ground pipeline project.

My Question is Wat factor i want to consider to calculate the bend angle or arc Length for Elastic bend, 5D hot Induction Bend & Field Cold bend? What data i want to refer to calculate for this? Is there any formula or we have to calculate based on the thumb rule? iam fresh in this area. please advise.

Thank You for being an active contributor and helping people.

For steel pipe 30"NPS 20 SCH,L= the length of the pipe 12m

a= the tangent length (the straight length to be provided at the end of pipe to facilitate the welding with the main line) 2m(minimum)

r= the bend radius is 40D

so,

My Question is Wat factor i want to consider to calculate the bend angle or arc Length? What data i want to refer to calculate this...can u plz tell me......this is mail id kannapiran.mech@gmail.com...

have you heard about formulae for calculating length of chord in a circle???

l= (pi*r*theta)/180

Hope this will be informative to you

Did you find a good answer to your question?

I have the same question ? ( 8" wt 0.322 API 5L X 42)

can you help me ?

In retrospect and with more maturity in Pipeline Designs, I have found out that the maximum Cold (Field) Bend Angles are not fixed for all pipelines, but are dependent on the Line Pipe Length, the Bend Radius which is determined from the codes (ASME B31.8 or B31.4 or any other).

Hence 2226 contribution to the thread is the best answer to my earlier question.

Thank u....