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Stress ratio from table 323.2.2B 1

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AliGrailly

Mechanical
Dec 8, 2020
72
Hi All

what s the stress ratio for pipe A333 thk 12.7 mm at design pressure 15 bar and temp -46 Centigrade? what s the min thk for this pipe ( it refers to table 323.3.1 ?
please give me the value


As Per table's(323.2.2B) note

GENERAL NOTES:
(a) The stress ratio is defined as the maximum of the following:
(1) circumferential pressure stress for the condition under consideration (here --->>>based on minimum pipe wall thickness<<<<here, less allowances)
divided by the basic allowable stress at the condition under consideration.

 
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This is a rather strange question. The code has the equation you need to calculate the required wall thickness for a given material and set of design conditions. The basic allowable stress comes from the appendix.

If none of this makes sense to you, you really need to get with a local piping engineer.

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

"All the world is a Spring"

All opinions expressed here are my own and not my company's.
 
you are mixing units. 12.7 is mm, or 0.50", where i'm guessing 8.625 is inches, and 20000 is psi.
 
So ... ((217.5×8.625×25.4)÷(2
×0.5×25.4))÷20,000=0.094 , is the stress ratio [0.094] correct?
 
almost, sort of.

SR =(P*D)/(2*t)/S

P = 217.5 psi
D = 8.625"
UT = 12.5% (undertolerance of pipe)
t = 0.438" (0.50"*UT) & remove corrosion or any other mechanical allowances.
S = 20,000 psi

so:
SR =(P*D)/(2*t)/S
SR =(217.5*8.625)/(2*0.438)/20,000
SR = 0.1072

A333 Gr.6 is a curve D material, therefore your MDMT reduction can be 217°F per Table 323.2.2B
BUT... since you have a curve D material, Table 323.2.2A lets you have a starting MDMT of -55°F for 0.50" nominal thickness. which means your stress ratio doesn't even matter because you are at -55°F either way.


 
Thanks
So according to above for the temp -46 Centigrade , this material with thk 12.7mm and temp -46 requires impact testing and if MDMT Starts from -48.3 , no need this test on material

 

Yes. 12.7mm nominal thickness of a curve D material does not require impact testing unless it is below -48.3°C.

You should also check table A-1. You would have seen that A333 Gr. 6 MDMT is given as -50°F so you didn't even need to do any MDMT lookups or calcs.

 
 https://files.engineering.com/getfile.aspx?folder=21c66802-66fb-46c7-8f18-8a3746dd2f2c&file=A333_6.pdf
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