Stress ratio from table 323.2.2B 1

[AliGrailly]

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.

 

[StressGuy]

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.

 

[Cobra17]

SR =(P*D)/(2*t)/S ~ 323.2.2(b)(1)

 

[AliGrailly]

((217.5×8.625)÷(2×12.7))÷20000=0.0036???

 

[Cobra17]

you are mixing units. 12.7 is mm, or 0.50", where i'm guessing 8.625 is inches, and 20000 is psi.

 

[AliGrailly]

So ... ((217.5×8.625×25.4)÷(2
×0.5×25.4))÷20,000=0.094 , is the stress ratio [0.094] correct?

 

[Cobra17]

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.

 

[AliGrailly]

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

 

[Cobra17]

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.