Thickness of coupling in calculation

[ElCidCampeador]

Ref. to this thread:

thread794-377365

my question is: what thickness should I use in calculation of threaded coupling acc to b16.11? The equivalent as per table 7 or (Outside diameter of coupling - Outside diameter of threaded pipe)/2?
Because they are different. My A.I. said the last one. thanks

 

[GenB]

B16;does not give you thickness. Your AI is correct.

General Blr. CA,USA

 

[ElCidCampeador]

B16;does not give you thickness. Your AI is correct.

So what is the meaning of table 7? When do you apply it?

 

[Jano6924]

See paragraphs 2.1.1 and 2.1.2, Table 2 and 3 in ASME B16.11

Regards.

 

[ElCidCampeador]

See paragraphs 2.1.1 and 2.1.2, Table 2 and 3 in ASME B16.11

I read it, but for me it's not clear.
Table 7 expresses a correlation between Fitting class and schedule No. What does it change in my calculation?

Moreover, does UG-45 apply for B16.11 couplings? Should I consider corrosion allowance in calcs? I know that these couplings are usually exempted in calcs, but If I would consider them? thanks

 

[ElCidCampeador]

Ref. to UG-45 question, I found interpretation VIII-1-83-217 quoted in ASME VIII Div.I Ed.'15, that says:

Interpretation: Vlll-1-83-217

Subject: Section Vlll-1, UG-11 and UG-45
Date Issued: February 22, 1984

Question: Are threaded couplings welded directly to a pressure vessel to be designed per ANSI B16.11 as stated in UG-11, footnote 5, Section VIII, Division 1, thus disregarding the requirements of UG-45 for nozzle neck thicknesses, since no neck exists?

Reply: Yes.

Is this still valid?

 

[r6155]

@ ElCidcampaeador
“Should I consider corrosion allowance in calcs?"

Mmmmm!!!!!!! . Please read ASME VIII Div 1 from page 1 to the end of Code up to the time to be clear for you.
Search "corrosion" and you can find 226 instances.

Regards
r6155

 

[ElCidCampeador]

Mmmmm!!!!!!! . Please read ASME VIII Div 1 from page 1 to the end of Code up to the time to be clear for you.
Search "corrosion" and you can find 226 instances.

I was referring to B16.11! I'm not so noob...

 

[r6155]

Allways corrosion is present in calculations in all standards and codes.

Regards
r6155

 

[Jano6924]

Assume you have a 0.75"-3000# coupling, to determine the MAWP of this component, and per paragraph 2.1.1 of B16.11, you shall use the nominal thickness of a 0.75" pipe Sch 160 (per Table 2), that is thk=0.219".

Then you shall deduct the pipe mill tolerance, 12.5%
Then you shall deduct the applicable thread height.
Then you shall deduct the corrosion allowance.

Use the appropiate equation from ASME VIII-1. For couplings I normally use App. 1 equations for cylinders, using the allowable stress of coupling material.

As for the VIII-1-83-217 interpretation, I'm not sure if it is still valid. It would be good if you can search further and share you findings.

Hope this helps.

 

[r6155]

@ Jano6924. You are using old edition. See actual ASME B16.11 2011

In table 7 for your example 0,75” threaded coupling class 3000 is pipe sch 160 , then in Table 1-4 thickness is 0,25”
(0,219” is after -12,5% pipe tolerance).

Regards
r6155

 

[GenB]

Your AI is correct, use the latest. Corr.All. need not be CO sidered per Code and it's at your or customer's option. Mfg Undertolerance need not be considered in B16 couplings.
You still may have to supply calculations specially for welding sizing and reinforcing,

General Blr. CA,USA

 

[ElCidCampeador]

Corr.All. need not be CO sidered per Code and it's at your or customer's option. Mfg Undertolerance need not be considered in B16 couplings.

Thanks GenB, but where do you exactly find this statement in ASME code? Is it clearly written that c.a. e w.u. need not to be considered?

 

[GenB]

Section II-A. Each Spec has written data. Pipe needs to consider Mfg undertolerance.

General Blr. CA,USA

 

[ElCidCampeador]

Section II-A. Each Spec has written data. Pipe needs to consider Mfg undertolerance.

I know it, but for A 350 LF2 threaded coupling B16.11?

 

[GenB]

B16 should apply to all allowable materials.


General Blr. CA,USA

 

[ElCidCampeador]

B16 should apply to all allowable materials.

Please answer me to this question: I have this A 350 LF2 threaded coupling B16.11. Do I have to consider corrosion allowance and wall undertolerance? If yes, where is it written in B16.11? Beacause I can't find any reference.

 

[GenB]

No undertolerance reqd for forgings per ASME Sect. II-A, if you don't find it in the Specs is because it does not apply. Second, you will not find it in B16, corrosion allowance is by design and used in Calculations in the different Sections of the Code.
Similar to plate Specs.

General Blr. CA,USA