Pipe length

[AO1958]

HI there,

I don't know if I am posting in the right section, nevertheless it seems to me the most suitable.

I am facing to following problem:

I'd like to know if exists a formula to calculate the original length of a bent pipe.

In this pipe are known:
- length of all straight parts
- pipe diameter
- pipe thickness
- bending angle (ex 30°)
- pipe material

I would suppose that bending would determine a change in pipe length.

What I am expecting is to get a formula that will give me a length as a function of known data.

Please, has anybody of you faced to this problem or could kindly suggest me some useful literature or link ?

Many thanks

 

[MikeHalloran]

You also need to know the bend radius.

Given that, just figure the total length of pipe along the centerline. That will get you pretty close to the developed length.



Mike Halloran
Pembroke Pines, FL, USA

 

[StevenHPerry]

I think you'll need the bend radius or diameter. A 30° bend could be miles long or inches long.

Otherwise, basic geometry should get you close enough. CRC's Standard Math Tables is a handy reference, but it's just the circumference of a circle that you're looking for.

- Steve Perry

 

[zdas04]

"Length" is a slippery concept in this context. The distance from end to end along the center line will not change in bending. The distance from end to end along the outer edge will increase and the distance from end to end along the inner edge will decrease. Which one did you want?

It is easiest to calculate the center line length (measure the straight "tangents", measure the bend radius and use the circumference of a circle over your 30[&deg], then add the bits together. The outside length will be longer by difference in circumference with a radius = cl radius + 1/2 pipe OD.

David

 

[BigInch]

Oh. Trick question. Like how long is a foot long hot dog if you tie the ends together, but backwards.

**********************
"Being GREEN isn't easy" ..Kermit

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

http://virtualpipeline.spaces.live.com/

 

[jte]

Big-

Would that be negative 1 foot?

jt

 

[BigInch]

Probably a complex foot, but might could be a hot dog pi [π] too.

**********************
"Being GREEN isn't easy" ..Kermit

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

http://virtualpipeline.spaces.live.com/

 

[AO1958]

Many thanks to all of you.


You are perfectly right, I need bend radius.

Concerning material, do you think that bending can determine some changes with respect of calculated length ?
I would suppose that is the pipe is bend, some elongation will appear.

Please, what do you think about it ?

 

[zdas04]

My Statics book says that at the center line the length does not change. There is elongation in the outer edge. There is compression in the inner edge.

David

 

[racookpe1978]

Purchased length of pipe will not change (with elongation).

Effective length of pipe for flow calc's doesn't change either. That is, actual catalog flow data for a short radius fitting, or long radius fitting (true elbow), will be significantly different from those for an extremely long bend radius "pipe" like for a spray manifold or around a tank wall.

If you have fittings, use those values. If you have "long bent pipe" use the (approximate) values you get from calc's based on centerline length.

 

[racookpe1978]

I have noticed that, after sufficient application of heat and stress (as found, for example, on the surface of grill lubricated with the neccesary amounts of coolant (er, beer) in the operator), the centerline of a foot long sausage tied end to end backwards becomes the outside, the inside becomes the outside, the outside falls on the centerlawn, and the ID becomes the OD butt proportional to the radius of the plate supporting said ODD ID and centerlawn.

 

[LSThill]

AO1958 (Industrial)

Reference you are looking for:

PFï standard ES-24
PIPE BENDING METHODS,TOLERANCES,PROCESS AND MATERIAL REQUIREMENTS

Also, due a advance serch in Eng-Tips.com for PIPE BENDING METHODS

 

[BigInch]

The tricky part is that bending reduces the outside radius wall thickness; stretching in one dimension causes thinning in the other two, and you can't reduce the wall thickness below prescribed minimums.

**********************
"Being GREEN isn't easy" ..Kermit

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

http://virtualpipeline.spaces.live.com/

 

[AAD1678]

As far as a formula I am not sure. We buy a lot of bent pipe from Tulsa Tube Bending and this was under the bending process. You may want to contact some one from thier Facility.

"Mechanical Pipe Bending and Physical Pipe Bending Effects
Like any cold or hot working process, bending pipe and tube alters the mechanical properties of the original material. After cold forming, yield and tensile strengths may rise approximately 10 percent; elongation may decrease approximately 15 percent. Bending of pipe and tube can distort the cross section. This depends on the quality of the pipe bending machine tooling, the difficulty of the pipe bend and the experience of the pipe bender. The greater the radius, the less the resulting distortion; the tighter the radius, the greater the distortion. The inner wall of the pipe bend undergoes compression that thickens the wall. Excessive compression, in the worst case, can fold the material causing wrinkles or waves. The outer bend wall undergoes tension that thins the back wall. These same forces tend to make a round pipe oval, with the widest dimension of the oval transverse to the plane of the bend."