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

 

[Asisraja D]

hi
i don't know whether this sheet might be useful for you or not but anyhow i am sharing this sheet.

Need review for pipe wall thickness calculation sheet for pipes under internal pressure - Pipelines, Piping and Fluid Mechanics engineering

Hi professionals i am a project engineer and i did some calculations part for calculating wall thickness for pipes under internal pressure as per ASME B31.3. i have attached the sheet here. This is just my work to submit to all of you for a review on the steps involved here and the Units i...

www.eng-tips.com

 

[goutam_freelance]

This thread is for high pressure piping.

I have done a comparison for calculated thicknesses for B31.1, B 31.3 Chapter IX and theory of elasticity.

The result is as follows:


The B31.3 Chapter IX shows significantly lower thickness. My guess for possible reasons are;
1. Higher allowable stress for B 31.3
2. Considering the critical stress at pipe outside surface, whereas max stress occurs at pipe inside.
3. Use of a formula significantly different from B31.1

 

[mariolucas75]

See B31.3 Chapter IX High Pressure Piping

Regards

Dear r6155,

Thank you so much for your help.... i would have an additional question: -
I did pipe thickness calculation using:

B31.3 2022
304.1.2 Straight Pipe Under Internal Pressure (Chapter II _ Design) - "AMSE ordinary" formula
and
K304.1.2 Straight Pipe Under Internal Pressure (Chapter IX High Pressure Piping)

For high pressure piping formula (34a) i got wall thickness slightly lower than using "ordinary" formula (3a).... I am curious using high pressure formula i got slightly lower thickness rather than ordinary formula ....​

 

[LittleInch]

I'm pretty sure that's right. The thick wall formula is more "precise" by about 5% to 10% from memory because at that thickness 5% makes a big difference.

I think it takes the mid wall location for the stress calculation.

 

[mariolucas75]

I'm pretty sure that's right. The thick wall formula is more "precise" by about 5% to 10% from memory because at that thickness 5% makes a big difference.

I think it takes the mid wall location for the stress calculation.

LittleInch,
Could you please advise me you mention above - about the iteration and introducing Y=d/(D+d) when t> D/6 to where and how ?

 

[LittleInch]

I will admit I'm more used to pipeline formula which are a bit different.

I think equation 34a is the one you want.

 

[GD2]

OP,
ASME B31.3 don't provide Code equations when t ≥ D/6 or P/SE > 0.385.
You must be aware that at higher wall thickness, the stress across the wall thickness is no more a membrane stress (equal/average) but rather becomes exponential. ASME B31.3 Chapter K is based on High Pressure Piping definition that is based on a ASME B16.5 Class 2500 P/T rating.
Because the Piping Codes are drawn from ASME BPVC, a better response to your query can be found in Mandatory Appendix 1 Para 1-2 (Cylindrical Shells) of ASME Sec VIII Div1 that follows the rule in your query.
Both equations in Chapter K and Sec VIII Div 1 MA 1 are in exponential form.
You have already done the thickness calc per Chapter K. Can you also do the calc using Div 1 MA 1? It will be interesting to see the result.