Calculating reduction in pipe diameter due to applied axial force

[bakal28]

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.

 

[desertfox]

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

 

[bakal28]

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

 

[desertfox]

Hi Nimajoef

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

 

[rconner]

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).

 

[bakal28]

Desertfox,

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

Good point rconner. Will do.