I'm interested in knowing from where the Sec VIII Div. 1 code formulaes have been developed. Eg: Can anybody tell me how thickness of cylindrical shell is t=P.R/(SE-0.6p). I can derive t=PR/SE. But from where did this 0.6P come from. I also want to know about the basis of formulaes used in UHX part for exchanger design. Can anyone tell some reference books which shows the derivation of these formulaes

Hello PV

The formula is derived from thick cylinder theory - also known as the Lame theorem.. The formula you derived is fairly accurate for cylinders whose t/D ratios are very small, but when the t/D ratio is greater than 10, then the derived hoop stress is not accurate.

ASME Section VIII, Division 1, Appendix 1-2 explains this where it uses thick cylinder theory.

Now the small factor '0.6P' slightly modifies the formula so that it approximates the thick cylinder formula. It is an approximation.

What about the exchanger design (UHX part of code)? Can anyone pls mention the books used in which these formulaes have been derived

Dear Ganesh,

Please refer to the book "Mechanical Design of Heat Exchangers and Pressure Vessel Components" by K.P. Singh and Alan I. Soler. This should give some background on the methodology. Whether or not the book is still available is a good question.

Ganesh,

You may also find this ASME white paper on part UHX useful. Here is the link,

http://www.coade.com/user/download/pvelite/UHX_wpaper.doc

It is long MS Word document about 4.7 Mb. But, it contains useful background information and comparison to other methods.

Dear Ganesh,
The ratio of ft/pt can be conventionly plotted against K by Maccary and Fey. The determination of shell thickness using lame's equation involves calculation by successive approximation. the same calculation using equation is more conveient, being a direct calculation, but membrane is limited in its application to vessel in which t/di is equal to or less than 10 mm. The range of membrane equation has been extended by the empirical modification of adding the constant 0.6. This new equation is known as ASME modified membrane equation and is much closer agreement with the lame's equation. At a t/di value of 0.25 the ASME modified membrane equation agree with the lame's equation with 1%.

You can refer book Process equipment design by Brownell & Young

It is to be remembered that the problem is simplified by using the code rules as found in ASME Section VIII, Division 1, Appendix 1-2. You have to abide by those rules anyway, as the Appendix is mandatory.

For the technical background, most mechanics of materials books give the derivation.

HI Mandeep ,

the above mentioned link is not opening


regards
Madhu

Hi Madhu,

It should work, I tried it. It is a large file, it may take a while depending upon the connection speed. Do you have MS Word on your computer, as this is a Word document.

Perhaps I should remind everyone that we should stick to one topic for each thread. If a new topic is to be introduced, that it would be better to start a new thread.