field cold bending 2

[pipeliner3000]

General rule of thumb for field cold bending (onshore pipelines) is 40D bend raius. Does anyone know the origin of this?
Further, for large diameter pipes this gives fairly sensible bends achievable for a double random pipe length (12m).
Calculated for 8" pipe using arclength = r * theta and assuming 10m bend arc you get 8.5degrees / m - 85 degress for one pipe joint...

I can't see 85degrees happening on a field bending machine. Is the machine the only limitation?

Is there a general rule of thumb that 10degrees per joint is maximum sensible bend... or am i missing something..!

 

[SNORGY]

The rule of thumb they refer to in CSA Z662-07 for 12"-D pipe is 1.5 degrees change in direction per pipe diameter of arc length.

I prefer to evaluate things in terms of outer fibre elongation; the ASME B31.3 Code for impact-tested material would limt outer fibre elongation to 5%. Since most line pipe in industry (here anyway) has some impact test qualification to Category III or Category II, you could probably "get away with" 5% elongation, but without field hardness testing I wouldn't want to go there.

I read somewhere in a myriad of articles about a year ago that common practice in the USA P/L industry is to limit outer fibre elongation to 2% - 3%, thereby permitting cold field bends in the (approximately) 25-D radius range.

Regards,

SNORGY.

 

[rneill]

You might want to look at the document ES-24 published by the Pipe Fabrication Institute as it provide some guidance on acceptable cold bend radius based on the method in use (type of machine).

General rules of thumb that I've used for cold bends are as follows:

10" and smaller with a polyethylene coating, no less than 30D (2 degress per diameter of length) to prevent damage to coating.

12" and larger with polyethylene coatings, no less than 40D (1.5 degrees per diameter of length).

All all pipe with fusion bonded epoxy coatings, no less than 40D (1.5 degrees per diameter of length).

For uncoated pipe, I default to the Design Code in use (B31.3, B31.4/8, or Z662). Note: Look at Clause 841.23 of B31.8 as I think it has quite a bit of guidance.

Note also that anything with fiber elongation more than 5% (a 10D bend) in sour service requires stress relieving or heat treatment per NACE MR0175/ISO 15156.

 

[BigInch]

In the pipeline codes B31.4 & B31.8
you will find the minimum permitted bend radaii in,

B31.4 PP 406.2
B31.8 PP 841.231

B31.4 is quoted as follows, and
BOTH CODES HAVE THE SAME IDENTICAL TABLE

(b) Except as permitted under para. 406.2.l(c), the
minimum radius of field cold bends shall be as follows:
Minimum Radius of
Nominal Pipe Size Bend in pipe Diameters
NPS 12 and smaller 18D
14 21
16 24
18 27
NPS 20 and larger 30


**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

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

 

[GregLamberson]

pipeliner3000

Depending on the pipe, you can generally get a little more than 10 degrees though. For example, currently working with some 24", X-65, 1.000" WT API 5L pipe and we are getting up to 12 degrees per joint with the cold bend trials.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[pipeliner3000]

Thanks, all suggests that 40D bend is not the minimum for 6" pipe. However, 40D gives 8.5 degrees per metre (85 degrees in 1 joint)that I don't believe can practically be pulled in on a standard field cold bending machine.

Any ideas what might be acheivable??

 

[BigInch]

Buy a 5D90 and field cut it.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

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

 

[rneill]

You could call your contractor and ask him what he can do with his machine?