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Div 2, Table 4.4.1 temperature limit for compressive stress

Div 2, Table 4.4.1 temperature limit for compressive stress

Div 2, Table 4.4.1 temperature limit for compressive stress

(OP)
Dear all,
Div 2, Table 4.4.1 sets the 800 F limit for many commonly used materials for compressive stress, that means I can not use the materials that I used to use if temp is exceeding 800F unless I switch to Div 1.

The compressive stress will occur at design temperature from weight, wind, seismic or vacuum, and not always below 800F. I have a hydrocracker reactor at 2500 psig and 850 F with 2 1/4Cr-1Mo or 2 1/4Cr-1Mo-1/4V. Years ago we built many from Div 2. But due to the temp limit, forcing us to use Div 1, more expensive with thicker wall.

Questions:
Why Div. 1 has no temperature limit ?

Why can't Div 1 and Div 2 come up with the same rules on compressive stress? Metal can not tell it is Div 1 or 2. People was talking about creep or rupture stress, but apparently Div 1 has no concern to set temp limit.

Any code case or interpretation that Div 2 is allowed to be used above 800 F for my reactor ?

Thanks for any of your opinion.


RE: Div 2, Table 4.4.1 temperature limit for compressive stress

Div 1 does have temperature limits on compression stresses. These are found in the appropriate figure in Section II Part D Subpart 3.

The materials you list are covered by Figure CS-2, and thus would be limited to 900°F for Div 1 compressive stresses.

It looks like Table 4.4.1 appeared in Div 2 in the 2007 edition, which is perhaps why you could go hotter (same temp limits as Div 1 though) years ago.

RE: Div 2, Table 4.4.1 temperature limit for compressive stress

The failure mode for compressive stresses is bucking. At and above those temperatures, you're dealing with creep buckling, which is a much more complex failure mechanism.

For thick-walled hydrotreater vessels, the minimal compressive stresses at temperature can likely be neglected using engineering judgement. But you need to be very cognizant of creep bucking nevertheless.

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