stress values to calculate pipe thickness 2

[jmoya]

Hi All,

I have a question concerning Code ASME B31.3-2006.
In 304.1.2.- Straight Pipe Under Internal Pressure are the equation (3a) and (3b) to calculate the pressure design thickness. Above, in 304.1.1 General (b) is defined S= stress value for material from Table A-1. In this table there are many materials, but my question is, what values of “S” I have to use for materials that are not in the table A-1?
I have found in ASME Sec II PART D – Properties (Metric) 2004 EDITION, Subpart 1 STRESS TABLE – Table 1A values of Maximum Allowable Stress. I am checking the same material in table A1 from B31.3 and in the table 1A from Sec II PART D, and the values doesn´t match. Are there any relation between this both tables? Can I use this values for calculate the equation (3a) or (3b) shows in ASME B.31.3?

Thanks in advance.

 

[sendelkr]

iam answering for your second part of the question first , the allowable stress value of ASME Sec II PART differs from b31.3 coz the factor of safety differs in both the case the factor of safety is higher 4 incase of ASME sec II and 3 incase of 31.3, ASME Sec II is generally refered for ASME BPVC and not for ASME 31.3.
now for the first part of your question ,i have not come across like this prob so can you provide me some material which doesnt exist so that i can give you the alternate

sendel kumar

 

[JohnBreen]

jmoya

What material do you want to use? Why are you NOT using a listed material?

What is the design Code required by the jurisdiction in which the piping system is to be installed?

If you are designing a piping system to the ASME B31.3 Process Piping Code and you want to determine the allowable stress for a material that is not listed in Appendix "A", read and understand paragraph 323.1.2. You can find the bases for the allowable stresses of B31.3 in paragraph 302.3 and its sub-paragraphs. READ AND UNDERSTAND paragraph 302.3 and its sub-paragraphs - ESPECIALLY 302.3.2(f). READ AND UNDERSTAND the footnote "2" referred to by paragraph 302.3.2.

You CANNOT use the allowable stresses from ANY other Code or Standard if you are designing to the rules of B31.3. B31.3 provides rules for using unlisted materials but you MUST comply with these rules.

Your questions are confusing because you say in your first question you cannot find the material in B31.3 Appendix "A" but in your second question you are asking why the Appendix "A" maximum allowable stresses at temperature do not agree with some other design Code. What material are you using?

Regards, John

 

[jte]

John answered the OP's question... I'll point out the error in Sendel's response (well, besides the sloppy typing):

The allowable stresses in ASME II-D 2004 have design margins which vary. They may be 3 or 3.5 or 2/3, and that is excluding the margins when external pressure or creep are involved. But, as far as I know, II-D 2004 has no design margin of 4 on its allowable tensile stresses.

jt

 

[ApC2Kp]

jmoya,

Your post "Material High Conditions"in the 'Steel and Stainless engineering' forum has the temperature as 1400 deg F and alloy 625 along with other dimensional information of Nps-0.5, 1., 1.5 for the 5076. psi service.

There is not much strength remaining for design at 1400 F. and the highest strength B619 / B622 of UNS 06002 appear to have 4.8 ksi for allowable at the 1400 F temperature.

Larger diameter sizes might use refractory linings as insulation to design with lower temperature / better strength. Difficult to do that in small diameters.

Metengr's comment about limited selections for this service is definitely under-stated.

 

[jmoya]

Hi All,
For example, the material SS 904L = 1.4539 = N08904.
In B31.3 tables is not defined this material (or I dont find). This material (UNS N08904) is name in "Specification Index for Appendix A" (page 134 B31.3-2006), but there is not values of stress at diferentent temperatures in the tables to used in thickness calculation. Nevertheless, in ASME-II PART D-2004, I find stress values (page 230-232 Line No. 28 Smls. pipe&tube SB-677).
This is the example of one material which have values in ASME-II PART D and no data in B31.3.
So, how a can calculate the pipe thinkness with according B31.3 ?

Thanks.

 

[JohnBreen]

......sigh!!!

"In B31.3 tables is not defined this material"

To do a required wall thickness calculation you need a Code allowable stress

"you want to determine the allowable stress for a material that is not listed in Appendix "A", read and understand paragraph 323.1.2. You can find the bases for the allowable stresses of B31.3 in paragraph 302.3 and its sub-paragraphs. READ AND UNDERSTAND paragraph 302.3 and its sub-paragraphs - ESPECIALLY 302.3.2(f). READ AND UNDERSTAND the footnote "2" referred to by paragraph 302.3.2."

So, how a can calculate the pipe thickness with according B31.3 ?

1. Determine the B31.3 allowable stress as was explained above.
2. Use the allowable stress in the B31.3 minimum required wall thickness calculation.

.....sigh.........