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ASME Sec VIII Dic 2 Table 4.4.1

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PVLead

Mechanical
Jun 8, 2020
6
If a vessel has a Design Temperature of 850°F for internal pressure and 350°F for external pressure, does Table 4.4.1 of Div 2 prohibit the use of low alloy material as material of construction for this pressure vessel? The material in consideration has allowable stresses up to 1000°F in Section II Part D.
 
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Do you have compressive stresses when the temperature is greater than 800°F?
 
There will be on the leeward side doing the wind analysis. Also in seismic analysis. These conditions never govern, always governing is internal pressure at design temperature.
 
Are the stresses actually compressive, or are the tensile stresses lower?

If the stresses are actually compressive, then the prohibition stands. The allowable stresses listed in Table 5/5A are allowable tensile stresses. In compressive stresses, the failure mode is buckling. Above the temperature listed in Table 4.4.1, the failure mode becomes creep buckling - which is something that the allowable tensile and compressive stresses do not consider.

You cannot make the determination of whether creep buckling governs unless you actually perform a creep buckling analysis - the calculations provided in Part 4.4 do not consider that failure mode. Therefore, you are unable to make the statement "These conditions never govern...".
 
Then the path forward is to go to Part 5 Design by Analysis which allows the material in question up to 900°F.
 
Exactly what material are you dealing with?

You didn't answer my question...
 
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