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Calculating reduction in pipe diameter due to applied axial force

Calculating reduction in pipe diameter due to applied axial force

Calculating reduction in pipe diameter due to applied axial force

(OP)
Hello everyone.

Can someone please advise whether my calculation of pipeline diameter reduction due to applied axial force is correct. Given are the following:

HDPE Pipe OD158, ID136
Length = 1000 m
Mod of Elasticity = 1300 MPa
Tensile Yield Strength = 26 MPa
Allowable axial pulling force = 50% of tensile yield strength

Using Hooke's law, I'm getting an elongation of 10 metres. With an assumed Poissons ratio of 0.35 (for short term stress) and using the formula v = E lateral / E axial, I only get a 0.6mm reduction. Was the calculation correct? or is there any other method of calculating this?

This HDPE pipe will be inserted as a liner to a steel pipe (ID 154), hence the need to reduce the diameter.

Appreciate any input.

 

RE: Calculating reduction in pipe diameter due to applied axial force

Hi Nimajoef

Well using you're figures I get a 10mm elongation in the length and a 3.5mm reduction in diameter.
I can see one error in your post above and thats an elongation of 10m that should be 10mm.

desertfox

RE: Calculating reduction in pipe diameter due to applied axial force

(OP)
Thanks for the reply desertfox.

In my calcs, I calculated the change in length by multiplying strain = elongation = change in length / original length. That gives me 10m. Same with change in diameter by factoring in v=0.35. I then get 0.55mm.  

Would you mind showing me your calcs? Thanks

RE: Calculating reduction in pipe diameter due to applied axial force

Hi Nimajoef

My mistake you're corect with 10m elongation, what values have you got for Eaxial and E lateral?

RE: Calculating reduction in pipe diameter due to applied axial force

You may want to check your hdpe pipe supplier on appplicability of parameters to this installation process (I think it is possible "short-term" might mean REAL short-term, as in tensile machine loading in a laboratory test, whereas long-term might mean modulus might go down pretty quick, and Poisson ratio up, with any meaningful actual installation pull duration).  

RE: Calculating reduction in pipe diameter due to applied axial force

(OP)
Desertfox,

I got E axial= 0.01 and E lateral = 0.0053.

Good point rconner. Will do.

 

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