Brewery Grinding Rooms

[RedTag]

Codes: 2012 IBC, IFC, 2019 NFPA 69

I have a brewery being built that has a grinding room for processing barley and other grains. The storage and use of grain is below the MAQ for IBC 415. My question revolves around table 414.5.1 and the commentary stating that the activities in the "special uses" section require deflagration prevention or control no matter the quantity used.

TABLE 414.5.1. See page 4-100.
This table designates when some methods of explosion
control are required for specific material or special
use conditions. The applicability of this table
assumes either the quantities of hazardous materials
involved exceed the maximum allowable quantities in
Table 307.1(1), listed in the table under “Hazard Category,”
or special explosion hazards exist as listed
under “Special Uses.” Section 911 of the IFC provides
design criteria for explosion (deflagration) venting.
Explosion prevention (suppression) systems,
where utilized, must comply with NFPA 69.

The room has an explosion-proof ventilation system to meet the explosion prevention requirements of IBC and NFPA 69, but what I can't seem to find is how to verify that the exhaust is large enough to prevent the possibility of explosion. NFPA states the deflagration prevention must maintain a level of < 25% of LFL (lower flammable limit) but I can't seem to find anything about what that limit is for grain dust or how to calculate the required air change to maintain < 25% LFL for a given room volume.

Hoping someone has some experience in this particular situation and can provide me some guidance. The mechanical engineer for this project is also having difficulty finding the same information so I thought I would ask here.

Thanks

 

[ADAguy]

Check with a midwest manufacturer of grain silos ?

 

[mtlogcabin]

The first thing to determine is if the dust will be combustible. If not then it is not hazardous

COMBUSTIBLE DUST. Finely divided solid material which is 420 microns or less in diameter and which, when dispersed in air in the proper proportions, could be ignited by a flame, spark or other source of ignition. Combustible dust will pass through a U.S. No. 40 standard sieve.

 

[RedTag]

The first thing to determine is if the dust will be combustible. If not then it is not hazardous

COMBUSTIBLE DUST. Finely divided solid material which is 420 microns or less in diameter and which, when dispersed in air in the proper proportions, could be ignited by a flame, spark or other source of ignition. Combustible dust will pass through a U.S. No. 40 standard sieve.

The issue is that table 414.5.1 specifically states that grain processing requires explosion control or venting under the special uses section. Combustible dust is a separate item not in the special use portion, thus is eliminated because they are less than MAQs. The table flat out requires explosion prevention or venting for all grain processing operations. If I was only looking at combustible dust, I could get away from the requirement by the definition you mention. Unfortunately, I can't get away from the definition of grain processing as that is exactly what is happening.

 

[RedTag]

Check with a midwest manufacturer of grain silos ?

I like that idea, I am just afraid that will get much more indepth than what is needed here. I am really just hoping to qualify the exhaust fan as being adequate to be considered the explosion prevention required by NFPA 69. I really don't feel like there is a risk as the grain processing is just splitting the grain and not grinding it like a flour mill. I just need to be able to point at a code and say "I approved because they meet the requirements of section..."

 

[ADAguy]

Better to have/acquire more knowledge than less.