FULL VACCUM TEMPERATURE

[thwilli2]

How do you determine the temperature that is associated with full vaccum? Also what part of ASME VIII can I find this information?

 

[mvelez]

in the phase equilibrium you will find a corresponding temp for each pressure level. on an industry level, you should never speak about full vacuum as it is in the practice, impossible to achieve. on an industrial enviroment you should always talk about a certain absolute pressure (regardless of how low it is). theoretcally, the temp asocciated with full vacuum for any substance should be -273K (also impossible to achieve as well as the 0 mBar abs pressure).

but you will never get a full vacuum in practice. In our plant we work at 0,3 mBar abs (not too much vacuum and yet it poses several challenges on the design, assembly and operation), and I Know vacuum pumps that work as low as 0,01 mBar. yet this is not full vacuum as I have read there are processes working at 0,001 mBar.

first, you should set a real, practical, measurable process pressure and then, go to the substance phase diagram and find the corresponding temperature of phase equilibrium.

hope it helps

mvelez

 

[mvelez]

sorry I meant -273°C (meaning 0 K)

 

[TD2K]

You really have to look at your process and identify how you could cause a vacuum to be formed and the resulting metal temperature.

That said, I've often seen vessels rated for full vacuum at 300 deg F.

 

[MJCronin]

This type of information is not contained in ASME VIII.

ASME DOES contain the methodology and rules necessary to design a vessel to sustain "full vacuum" conditions.

"Full vacuum" will never exist, as stated above....... but this loading condition is commonly specified in process vessel design.

Suggest that you become familiar with the structure, scope and intention of the many Pressure Vessel codes....

 

[mvelez]

I have two evaporators working at 0,3 mBara (which is 0,000435 psia) and 380°C (which is 716 F)

 

[gerhardl]

twilli2:

Could you please explain? Do you need this for dimensioning the strength of a vessel that is dimensioned to be operated at a created given vacuum, or to dimension for a vessel where (for instance) cleaning steam suddenly cools (collapsing from steam to condensed water) and creates a vacuum?

The last you might find if you search for dimensioning of busrsting discs. You can then select a disc dimension, check the amount necessary and timerate, and dimension your resistance against vacuum at a safe limit below.

 

[racookpe1978]

I have two evaporators working at 0,3 mBara (which is 0,000435 psia) and 380°C (which is 716 F)

In the other direction NASA has pressurized vessel working in space at -273C and 00.00 vacuum. But I don't think the original poster is using either of our two conditions. 8<)