ASME VIII Div1 3

[InspectionSoftware]

Presently dealing with a Close Drain Vessel.
ASME Code Section VIII. Div1 Ed 98 Add 2000
What is the correct formula for Min Wall Thickness?

 

[metengr]

You will need more than just the formula, you need the joint efficiency factor and allowable stress value for the vessel material. These are all available in ASME Section VIII, Div 1 and Section II, Part D.

 

[InspectionSoftware]

I have ALL the data...I just need the correct Formula

 

[TGS4]

I think what metengr is trying to say is that you'll need to get the book yourself, read it, understand it, and then apply it. In your case, I would probably add - hire an engineer experienced in the design or pressure vessels.

 

[panduru]

techsolutions:
The formula comes two parts: the letter and the spirit, so to speak. One needs to have an understanding of the principles behind the formula before applying it. The assumptions and "what were they thinking when they said ... in the code" kinda insight.

 

[proinwv2]

I agree, don't just have someone send you an equation. There is more to it than that. The code is not a scientific documnent. It is a combination of engineering science and experience factors.

Either read and understand that portion of the code, or hire a consultant who can do so for you.

Paul Ostand

http://www.ostand.com

 

[InspectionSoftware]

Hey Guys! Cool Down....
I understand very clearly the implications, experience etc.. of these equations!

All I requested was the basic equation.

I need to double verify the equation in the software design code.

Presently, for example, I have four different equations for Wall Thickness on B31.8 Gas Lines.

I also have a querie on B31.3 D<6". Which was current in the 1990's.

So whilst I appreciate your comments on hiring an Engineer. I am One!

 

[TGS4]

t=(D/2)*(exp(P/(S*E))-1)

This equation is without regard to the thickness ratio (D/t).

 

[lostsailor]

techsolutions,
Assuming you are talking about shells, the ASME VIII-1 reference you are looking for is UG-27 "Thickness of Shells Under Internal Pressure". These equations are:
t=(PR)/(SE-0.6P) circumferential stress (longitudinal joints)

t=(PR)/(2SE+.4P) longitudinal stress (circumferential joints)

no offense but being an engineer and being an engineer well versed in the application of the ASME B&PV Codes are not the same thing.
Regards,
RLS

 

[arto]

You can get all the current ASME codes etc online if you have an IHS subscription [expensive, but worth it

http://www.ihserc.com/

].

It might be a good idea to check your software versus the current document, rather than us guys here typing in equations. Kinda like basing your design on free internet software....



Remember John Ruskin:
""It's unwise to pay too much, but it's unwise to pay too little too. When you pay too much, you lose a little money.....that is all. When you pay too little, you sometimes lose everything because the thing you bought was incapable of doing the thing it was bought to do.

The Common Law of business balance prohibits paying a little and getting a lot...it can't be done. If you deal with the lowest bidder, it is well to add something for the risk you run, and if you do that, you will have enough to pay for something better."
"

p.s. an experienced P.V. engineer woulda said "I are one" ;-)

 

[panduru]

TGS4:

" t=(D/2)*(exp(P/(S*E))-1)
This equation is without regard to the thickness ratio (D/t). "

Huh, tgs4? Sorry, but I've not come across this eqn before. Could u pl throw a little more light on this one? And while u are at it, what is the qualifier "is without regard to the thickness ratio" ? I see that both t and D do figure in the eqn anyway.

Thanks.

 

[TGS4]

This is the "exact" formulation for calculating thickness in a cylinder - it is the more general formulation of the Lamé equations. Whereas the simple t=PD/(2SE) is limited to thin-shells (D/t>10), the above formula is "exact", and therefore not limited to any D/t ratios.

 

[PAN]

TGS4,
I found the limit of use Barlow's formula in ASME B31.3 for thin-wall (D/t > 6). This is difference from D/t > 10 in your post. Please advise me about the difference.

 

[unclesyd]

Some discussion about wall thickness using different formula. Read the whole article.

http://www-training.llnl.gov/training/hc/5060/Design.html#wall

 

[TGS4]

The "limit" is based on the error that you are willing to accept. In ASME VIII, Div. 1, that limit is D/t<10., while in B31.3 that limit is D/t<6. The different committees had a different view of acceptable error. I don't see anything wrong with that...

 

[PAN]

TGS4,
Thanks for your advice. I understand that UG-27 does not mention about D/t > 10. I found this limit only in UG-28 (external pressure design).

 

[prex]

TGS4,
the limit on D/t ratio is not a matter of error, but of economy. The standard formula for thin cylinder (with all the numerous slight variations) will overestimate the thickness for a thick cylinder: codes that provide a different formula do that only to avoid an unnecessary conservativism.

prex

http://www.xcalcs.com

Online tools for structural design