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“Factory Mutual Data Sheet 8-9 Storage of Class 1, 2, 3, 4 and Plastic Commodities” is Factory Mutual’s (FM) version of the storage chapters of NFPA 13 (Chapters 12 through 17). You will need to be familiar with Data Sheet 8-9 in the event your storage sprinkler system must comply with FM criteria. The other reason you may wish to become familiar with the criteria in this document is that Data Sheet 8-9 addresses storage protection options that are currently not available in the most recent edition NFPA 13.
Of course, if you use Data Sheet 8-9 as a substitute for design criteria of NFPA 13, you will need to get the approval of the AHJ. In addition, your sprinkler system must adhere to all applicable FM criteria, including “FM Data Sheet 2-0, Installation Guidelines for Automatic Sprinklers” (see the December 2011 issue Plumbing Engineer for my column on this data sheet). Sprinklers must be FM Approved, as well as, other system components.
Data Sheet 8-9 presents the protection options in a manner that a bit different than NFPA 13. It even uses color. Whether or not it is easier to apply is something I will leave up to you.
FM recognizes eight storage commodity hazards, which are, ranked lowest to highest hazard.
1. Class 1
2. Class 2
3. Class 3
4. Class 4
5. Cartoned Unexpanded Plastic
6. Cartoned Expanded Plastic
7. Uncartoned Unexpanded Plastic
8. Uncartoned Expanded Plastic
NFPA 13 has seven commodity hazards, Class 1 to 4 commodities and Group A, B and C plastics.
“FM Data Sheet 8-1 Commodity Classification” offers assistance in identifying the commodity hazard of your storage.
Data Sheet 8-9 organizes its eight commodity hazards into five distinct protection classes, lumping Class 1, 2, and 3 commodities into one group, and Class 4 commodities and cartooned-unexpanded plastics into a second group. The remaining three commodity hazards cartoned-expanded, uncartoned-unexpanded, and uncartoned-expanded remain as distinct groups.
The protection criteria for ceiling level protection, without in-rack sprinklers, are then placed in 10 different tables. There are five tables, Tables 2 through 6, (one for each commodity grouping) for solid-piled, palletized, shelf, or bin-box storage, and five tables, Tables 7 through 11, for in-rack storage. Oh yes, and there is Table 1. Table 1 establishes minimum and maximum ceiling sprinkler linear spacing and area limitations, based on ceiling height, k-factor, sprinkler orientation, and RTI rating. Sprinkler area of coverage varies typically from 64 to 100 square feet. Under certain conditions, K25.2 sprinklers can have larger areas.
The current edition of NFPA 13 does not offer a protection scheme for uncartoned-expanded plastics stored in-racks. It appears the 2016 edition of NFPA 13 will offer such a scheme restricted to the use of ESFR sprinklers. Data Sheet 8-9 offers several protection schemes using both quick response and standard response sprinklers.
The protection criteria is determined based on the following:
• System type - wet pipe or dry pipe
• Sprinkler orientation - pendent or upright
• Sprinkler RTI rating - quick response or standard response.
• Sprinkler k-factor
• Ceiling height. Depending on the protection group, options are available for buildings with ceilings as high as 45 feet.
Note that Data Sheet 8-9 no longer considers height of storage and aisle width as factors when determining protection options.
Also, note that only the upright standard response option is available for dry pipe systems.
All ceiling-level sprinkler protection options are defined by 1) the number of operating sprinklers and 2) the minimum operating pressure.
Data Sheet 8-9 contains no protection schemes involving the Control Mode Density/Area methods using density/area curves, still available in NFPA 13.
As for color, green is used in the tables to identify which protection options have a hose stream allowance of 250 gpm. Those options without color require a 500 gpm hose allowance.
Now things start to get a bit more complicated when the protection scheme involves in-rack sprinklers. When a protection scheme is not available with ceiling-only protection from Tables 7, 11 in-rack sprinklers are needed.
Data Sheet 8-9 Figure 3 provides a flow chart to assist in determining if in-rack sprinklers are needed.
Now FM has established two basic horizontal in-rack sprinkler layouts. IRAS(EO) represents in-rack sprinklers spaced horizontally at every other transverse flue space intersection between pallet loads. IRAS(E) represents in-rack sprinklers spaced horizontally at every transverse flue space intersection between pallet loads. Data Sheet 8-9 offers several flow charts to help determine the needed in-rack sprinkler arrangements both horizontally and vertically.
Now, if you have hung in up to this point you can use Table 12 to determine the minimum flow for each in-rack sprinkler, either 22 or 30 gpm, based on commodity hazard and number of levels of in-rack sprinklers. One now goes to Table 13 to determine the applicable ceiling height to establish the ceiling-level sprinkler protection requirements from Tables 7 through 11. This is determined based on commodity hazard, IRAS(EO) or IRAS(E), storage height above top level of rack sprinklers, and clearance between ceiling height and top of storage. Of course, with a careful reading of Data Sheet 8-9 you will find the procedure for in-rack sprinkler design much easier to follow than the abbreviated description I have provided here.
Our office has never had the opportunity to design storage protection for buildings that have extremely high storage. The warehouses we have been involved are typically 40 feet or less in height. We make every effort to avoid the use of in-rack sprinklers, something the users understand and appreciate. The protection schemes presented in FM Data Sheet 8-9 have helped us in that effort.
Samuel S. Dannaway, PE, is a registered fire protection engineer and mechanical engineer with bachelor’s and master’s degrees from the University of Maryland Department of Fire Protection Engineering. He is past president and a Fellow of the Society of Fire Protection Engineers. He is president of S. S. Dannaway Associates Inc., a 15-person fire protection engineering firm with offices in Honolulu and Guam. He can be reached via email at SDannaway@ssdafire.com.