Vessels with brittle steel

[BrittleSteel]

Hi everyone,

I was reading this CSB report that came out last year:

https://www.csb.gov/husky-energy-superior-refinery-explosion-and-fire/

One of the issues they mentioned in the report is that since the vessels were made of SA-212B and SA-201, brittle fracture occurred instead of a fish mouth rupture thus pieces of steel may dangerous projectiles.

My understanding is that this explosion occurred due to a fire case not because of a blocked discharge.

My first question is, did the metal projectiles get its energy from the heat generated rather than pressure? usually when some think about projectiles from a vessel failure many think of an overpressure scenario.

My second question is if the pressure vessel was designed for a fire case, would this failure still had occurred?

Last question is any pressure vessel that is made of a brittle material can fail in a similar manner if it's possible that enough energy is generated in the vessel to exceed its energy dissipation capacity. Is this correct?

 

[MJCronin]

Suggest that you repost in the "Boiler and Pressure Vessel" forum

Better eyes there ...

MJCronin
Sr. Process Engineer

 

[EdStainless]

The steel doesn't care if the pressure is caused by fire or process, over pressure is over pressure.
However in most processes there are many factors that limit how high and how fast the pressure can change.
If anything in a fire situation you would expect better ductility at higher temperatures.
If anything this case points out the need to periodically do a risk assessment from scratch, and not just update old assumptions.

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P.E. Metallurgy, consulting work welcomed

 

[BrittleSteel]

Thanks MJcronin.

Edstainless:

this may be a broad question but if one has a brittle vessel and analysis shows there is a risk enough energy can accumulate causing it to fracture similarly to this case study, is there any other option to address this instead of a pressure vessel replacement?

 

[EdStainless]

Safeguards to assure lower pressures are never exceeded.
Other than that, No.

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P.E. Metallurgy, consulting work welcomed

 

[georgeverghese]

The primary absorber downstream of the FCC may have been operating on refrigerated lean cycle oil, and the absorber may have developed microscopic cracks some time prior to this internal explosion that took place

 

[TugboatEng]

Could a brittle vessel be more prone to cracking and failure due to uneven thermal stresses caused by events such as a fire?

A brittle or ductile vessel is going to fail if stresses due to internal pressure exceed yield. However, a brittle vessel may be more likely to crack in the vicinity of restraints such as supports and nozzles during a fire due to thermal expansion. Just a thought.