limit between thick wall and thin wall pipes

[engahmedbahgat]

good after noon everyone , I need to know what is the limit between thick and thin wall pipes, I think that the value of pipe diameter to pipe wall thickness (D/t) is the key value in this case, but I need some one to confirm that with me and to clarify the value which distinguishing between thick and thin wall pipes, thank you in advance

 

[LittleInch]

The only definition I've ever seen is in PD (formerly BS) 8010 which provides a different wall thickness calculation for pipes with a D/t <= 20.

Otherwise in common usage thick and thin wall pipes simply refer to those pipes designed to a DF of 0.72 or 0.8 ("thin") and those designed to 0.3 or 0.4 ("thick") used for road, rail and river crossings or for proximity to occupied buildings or in a location class different to the "main" pipeline where thinner wall pipe is predominant.

This thickness is therefore pipeline dependant and has no limit or definition other than design factor differences.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[BigInch]

simply stated, a pipe basically becomes "thick-walled" when the difference between hoop stresses calculated by P x D_o/(2t) and P x D_i/(2t) can no longer be ignored.

http://courses.washington.edu/me354a/Thick Walled Cylinders.pdf

you must get smarter than the software you're using.

 

[dhengr]

Engahmedbahgat:
Thick walled vs. thin walled pipe is really a matter of their stress analysis, Theory of Elasticity, Lame’s Equations, and the various/different ways thin pipe vs. thick pipe buckle under external loading. This leads to two different design methods and slightly different thinking w.r.t. the two situations. LittleInch’s D/t < or = 20 is in the right range/region (approx. dividing line) separating the two methods. I don’t know what ‘PD or DF’ mean or say, but his comment “ used for road, rail and river crossings or for proximity to occupied buildings or in a location class different to the "main" pipeline where thinner wall pipe is predominant” is in keeping with my understanding, because the former conditions may involve external loadings on the pipe, and crushing or buckling, while the main line has a more uniform radial external loading. Thin walled analysis basically ignores radial stress variations and assumes an average circumferential stress through the thickness, based on the mid-radius and the thinner t for calcs.

BigInch’s link starts to delve into the Theory of Elasticity of the thick walled problem, and Lame’s equations. And, you have to be a little careful because some of the literature talks in terms of t/R and other literature/authors talk in terms of D/t, one being the inverse of the other with a factor of 2 thrown in for added confusion. For the most part, this approach is the more correct and accurate, but more complex too. This method has been applied to thinner and thinner pipe walls for a given D value [larger D/t’s or smaller t/R’s] until the difference in calc’ed. stresses when compared with the thin walled (simplified) method are within an acceptable per cent difference range, and that is called the dividing line btwn. thick and thin. Of course, this is subjective and up to the judgement of the researcher and is also dependant upon external forces too. So, the dividing line is really not well defined, or a specific number. The important thing is to understand the logic and methods of the two situations, and then use your engineering judgement in applying them.

 

[engahmedbahgat]

thank you all, for your effort and valuable information