Toluene tank and nitrogen pad

[SrChemE]

Hello,
One of our plants has a nitrogen tank that is not padded with nitrogen, it is a in-ground tank.
And similarly, another toluene tank, above ground does have a nitrogen pad.
Are toluene tanks required to have a nitrogen pad to protect against fire potential?
Thank you,
sarah

 

[MJCronin]

Toluene is a Static-Accumulating Flammable Liquid That Can Form an Ignitable Vapor-Air Mixtures.

There have been toluene storage tank explosions and fires in the past

https://en.wikipedia.org/wiki/Toluene

Non blanketed tanks of highly flammable liquids can be a danger from many sources:

https://www.csb.gov/csb-issues-fina...liquids-safety-video-with-animation-released/

More information on tank blanketing here:

https://www.processingmagazine.com/...nerting-for-flammable-and-combustible-liquids

MJCronin
Sr. Process Engineer

 

[LittleInch]

One of our plants has a nitrogen tank that is not padded with nitrogen

Is this a typo? A nitrogen tank very v clearly has a nitrogen blanket. Did you mean some other sort of liquid?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[SrChemE]

Yes, this was a typo. I meant to say toluene tank.
Our toluene tanks don't have a nitrogen pad, but have flame arrestors included as passive isolation techniques, we assume this approach was chosen in the past as the preferred way to preventing and controlling toluene tank explosions.
Would this be an acceptable design?
Thank you!

 

[don1980]

As you know, ignition of flammable vapors inside a tank must be reliably prevented. But how that's accomplished is up to the tank owner. One may choose to tolerate a flammable atmosphere inside the tank, and prevent ignition by use of a flame arrester. Or, one may choose to use a N2 pad to prevent the tank's vapor from becoming ignitable, thus allowing the flame arrester to be omitted. It's up to the tank owner to determine which alternative is best for them.

 

[MJCronin]

This topic has been examined before on another forum ... There seems to be considerable disagreement on the substitution of a FA for a nitrogen blanketing system

http://www.cheresources.com/invision/topic/24166-methanol-tank-venting/

https://www.cheresources.com/invisi...red-with-nitrogen-blanketing-api-2000-7th-ed/

https://www.eng-tips.com/viewthread.cfm?qid=374559

https://www.eng-tips.com/viewthread.cfm?qid=243184

MJCronin
Sr. Process Engineer

 

[SrChemE]

MJCronin,
Thank you so much for the links and additional information on this topic.

I was wondering if adding a N2 pad to a tank has some environmental permitting concerns that more toluene would be pushed to atmosphere through the breather?

Thank you.

 

[Latexman]

No change environmentally. You are switching your gas blanket from 79%/21% N2/O2 to 100% N2.

Good Luck,
Latexman

 

[pierreick]

Hi ,
You did not mention anything about lightning protection , is it in place in your storage tank area?
I do remember a place in China where a wall was erected between the storage tank (toluene) and office to protect the people from a blast. My point is to tell you that Toluene is a dangerous product , take a look at MSDS .

Pierre

 

[MJCronin]

Does anyone have the "final word" on the equivalency between a nitrogen blanketing system and a flame arrestor on the tank vent ?

I am not comfortable with a lot of opinions, recollections and recommendations.....

I would assume that the vendors of these systems and components would have a strong recommendation.

How are the rest of the world approaching this issue ?.... What are they doing in conservative Europe ???

.... or am I a rapidly aging Mechanical Engineering dotard sticking his nose in where it doesn't belong ????


ANYONE ?????

Best regards to all

MJC

MJCronin
Sr. Process Engineer

 

[jari001]

I would also take into consideration what is easier to maintain for the particular site (flame arrestor vs. nitrogen pad system components) and the implications on tank availability during maintenance. Properly maintained safety element(s) are the only ones that count.

 

[TiCl4]

I don't think there is a "final" word, unless governmental specific regulations require adherence to a code that requires one or the other. A flame arrester and N2 blanket prevent internal deflagration in two very different ways. The N2 blanket prevents internal deflagration from both internal and external ignition sources, while the flame arrester quenches the flame front (hopefully) before it can enter the tank headspace. A FA, however, does nothing to prevent any deflagration resulting from an internal ignition source. Providing an inerting gas feed to a tank, however, naturally comes with the downside of making confined space entry have an additional risk to consider from an oxygen deficiency point of view.

In my mind an inert blanket provide a much greater level of safety than does a FA, and is the preferred method for risk reduction for flammable storage of fixed-roof tanks. There have been events in the past that have been attributed to internal ignition (see USCSB video:

https://www.youtube.com/watch?v=tVZzdtnZaJk

), either from moving internal metallic components or free-falling flammable liquids. There are caveats, of course, like if O2 in the headspace is required - ala monomer storage.

 

[don1980]

MjCronin - Flame arrester vendors do indeed have a strong recommendation. No surprise, they recommend a flame arrester. But that's doesn't address the question of wheather or not there's a regulation requiring the inerting or the installation of a flame arrester. Do users have the option of making this risk management decision for themselves? That answer is yes.

 

[SrChemE]

Many thanks for all your inputs and attached links. This discussion was very informative.