In the 2016 edition of the NFPA 13, Table 13.2.1 in the part of "Group A Plastic Storage", in the paragraph of "Exposed", there is an option of "Expanded" and an option of "Unexpanded and Expanded".
Link: https://link.nfpa.org/free-access/publications/13/2016 There are two storage arrangements that end up with OH2 with +1 Level of In-Rack (all other criteria are the same):
It seems that the second option will always be better than the first option in reference to the permitted storage height. Why have the maximum 10 feet storage option if you can always go for the maximum 12 feet storage option? (Even for a building that is lower than 20 feet, you can go according to the option of storage of 12 feet in a building that is up to 32 feet) Thanks in advance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe
13 Comments
Dan Wilder
10/21/2022 08:25:38 am
Looking into the handbook commentary, the only conclusion I can come up with is the ability to use QR reduction but in using that smaller HMRA, the storage height is limited to 10' (in a 20' building) vs the ability to utilize the full 12' for Misc Storage (for buildings up to 32'). It also plays into the use of HMRA increases for sloped ceilings.
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Jesse
10/21/2022 08:42:22 am
In the EXPANDED row, all commodity in that storage array is expanded Group A.
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Dan Wilder
10/21/2022 08:53:22 am
Since I don't get into this near as much as I would like to..
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Jesse
10/21/2022 08:43:56 am
So if your storage array ONLY includes expanded Group A plastic products, you have to use the >5 to <10 design criteria.
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Franck
10/21/2022 12:16:14 pm
Jesse, that's not correct.
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Eric R
10/21/2022 10:10:58 am
Jesse, I don't believe you are correct. This chart doesn't make any determinations on mixing of commodities.
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Franck
10/21/2022 12:12:56 pm
That's the perfect answer !
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Zecharya
10/22/2022 11:48:54 am
Thanks Eric for your detailed answer!
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Eric R
10/22/2022 12:11:52 pm
Only for Class 1-4 commodities. If the commodity is classified as a group A plastic then this table can’t be used unless the storage area is small enough to be considered miscellaneous storage.
Zecharya
10/22/2022 11:31:42 pm
Eric,
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Eric R
10/23/2022 12:04:00 pm
13.1.1 is where this is delineated.
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Zecharya
10/23/2022 12:12:50 pm
You are absolutely correct!
Eric R
10/23/2022 12:22:06 pm
https://www.youtube.com/watch?v=xHiAl-TnqCY
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