Thick wall / high pressure pipe wall thickness calculations

[mariolucas75]

Dear All,

For pipe thickness calculations:

API 574 says for metallic pipe for which t ≥ D/6 or P/SE > 0.385 requires special consideration.
What is this special consideration? Where shall i find it ?

ASME 31.3 Para 304 Straight pipe under internal pressure says:
For t ≥ D/6 or for P/SE > 0.385, calculation of pressure design thickness for straight pipe requires special consideration of factors such as theory of failure, effects of fatigue, and thermal stress.

So, ultimately where is this formula available for thick wall / higher pressure (t ≥ D/6 or for P/SE > 0.385) pipe wall calculations ?

Thank you

 

[goutam_freelance]

See ANSI B 31.1, Cl. 101.4.2 and Table 104.2.1-1 where a factor y has been defined for D0/tm<6.

 

[r6155]

B31.3 2022 is clear: see 304.1.2

Regards

 

[mariolucas75]

B31.3 2022 is clear: see 304.1.2

Regards

Dear r6155:
B31.3 2022 Par 304.1.2 is about t < D/6, however i am interested when t ≥ D/6 or P/SE > 0.385....

 

[mariolucas75]

See ANSI B 31.1, Cl. 101.4.2 and Table 104.2.1-1 where a factor y has been defined for D0/tm<6.

Dear Gautam,
Thank you for the reply .... let me ask you the following also: ASME B 31.1 - 2016 Table 104.1.2 (A) values for y:

In notes it does address to the case when D/t<6 and gives a formula for y=d/(d+D)... Here i am confused - if i know d-internal diameter and D external diameter it means i already know the thickness between them - wall thickness... which in fact i try to figure out

 

[LittleInch]

I think you just need to iterate on t to see if the calculation works.

 

[goutam_freelance]

@LittleInch

Correct!

 

[mariolucas75]

???

 

[r6155]

See definition of Y in 304.1.1

Regards

 

[mariolucas75]

That's exactly what i don't understand Y=d/(D+d)
If i know D - Outside Diameter and d-inside diameter then i know the thickness it means t=(D-d)/2
why would i need the formula for t = PD/2(SE+PY) and putting in there Y=d/(D+d) ?

 

[NovaStark]

That's exactly what i don't understand Y=d/(D+d)
If i know D - Outside Diameter and d-inside diameter then i know the thickness it means t=(D-d)/2
why would i need the formula for t = PD/2(SE+PY) and putting in there Y=d/(D+d) ?

The formula stated in the code of t = PD/2(SE+PY) is used assuming the pipe is thin such that t < D/6.

If you have a situation where t>= D/6 or P/SE >0.385 then you won't be able to use the above equation as the basis is not a thin pipe anymore.

At that point, you would be likely needing to do some sort of further analysis, or use Lame's equations to minimize stresses through a selected thickness.

I have never done that kind of calculation before (that I can remember), so I can't say for certainty where the Y formula would come into play.

 

[FacEngrPE]

See the attached paper on stress in thick walled cylinders with closed ends. The calculations are more difficult than are used in B31.1 or 31.3.

 

[r6155]

See B31.3 Chapter IX High Pressure Piping

Regards