PSV sizing - fire exposure

[cswosu]

My question concerns sizing a pressure relief valve based on fire exposure. When calculating the heat absorption across the unwetted surface of a vessel, API 520 recommends using 1100 F as the vessel wall temperature for a carbon steel vessel. Anyone know what wall temperature to use for aluminum?

Thanks.

-Craig Ward

 

[EGT01]

Interesting question, one for which I would like to know the answer. I don't have any experience with aluminum but here's a couple of references to consider if you don't get a direct answer.

ASME B96.1, Welded Aluminum Alloy Storage Tanks (atmospheric storage) has a table of "Allowable Tensile Stresses for Shell Construction" for different alloys but their temperature range only goes up to 400F.

Also, check this link on the web regarding Department of Transportation, aluminum cylinders

http://hazmat.dot.gov/rules/67fr-51625.htm

Of course you probably already know this but to quote a section from the above link "Aluminum undergoes a marked reduction in tensile strength when subjected to high temperatures. This occurs at much lower temperatures than for steel cylinders."

There is some discussion about different aluminum alloys considered acceptable to use and when a cylinder was considered "over-heated". For aluminum they considered it over-heated at 350F and that is compared to a steel cylinder that was considered over-heated at 650F. However, seems that firefighters were taking exception to the 350F temperature saying their SCBAs were probably subjected to higher temperatures when going into a fire.

There was also mention of a publication "Aluminum Standards and Data 1993", published by the Aluminum Association Inc that might be something to check.

Just curious, what have you determined for you relief temperature?

 

[EGT01]

Happen to come across this thread about aluminum pressure vessels when searching for some other info and thought you might find it interesting.

thread794-47925

 

[Bensley]

Has anyone ever come accross a blind installed in a PSV process gas relief line to a flare header, as a means of isolating a PSV in a double sited PSV system?
There are no isolation valve fitted in either of the discharge sides of the two PSV valve only the blind in the closed position in the oddline PSV?

In this situation to commission the spare PSV valve the whole flare line would have to be depressured and gas free before the blind could be removed?

I would think, expect that this "set up" is against at least the safety code of practice, but cannot find the code or section, unless someone can give an valid expanation?

 

[EGT01]

Bensley,

No disrespect intended but, your questions are unrelated to the topic that cswosu wanted to discuss here. May I suggest you start a new thread and allow this thread to continue as started. By starting a new thread with a topic more related to your questions you may find that you get responses more to your interest.

Just as additional info, see FAQ731-376 regarding other Site Policies.

Regards,
Ellis

 

[cswosu]

Thanks for the responses, EGT01. I still haven't come across any official answer, but 300-350F seems to be the cutoff after which the aluminum starts to lose its strength and may not last for long at higher relief pressures. I'll probably stick with that temp range for my calculations.

Thanks again.