Jim: Your comments about area of activation in shielded large unit commodity is borne out by one fire I am familiar with.
4'w x 8-12' lx 4'h styrofoam units. Fire progressively caused pile collapse, and spread on under sides of blocks. 0.39 gpm /sf over 5,600 sf., nominal 100 sf spacing. 33 heads operated. The comments I find implied and not explicit in Jim's comments is that a slower fire spread might be expected, but that extinguishment will require a combination of sprinklers and several hose lines. This implies a fire department large enough to maintain maybe 12-18 FF's inside, for maybe an hour or two. This does not count FF's involved in pump operations, command, RIT , out getting new SCBA bottles, or rehab. Included is ability to recharge SCBA bottles. Do not expect a small fire department in an isolated town to necessarily be able to maintain the siege that may be necessary to beat this fire. It is also a hazardous fire. Extended fires in piles, even or especially slow spreading ones are dangerous. Fire brigade in Lewiston Idaho lost FF's fighting such a fire in roll paper. The first hose line and sprinklers may get it. Don't tell anyone that scenario is the only likely one. Yours, bv ----- Original Message ----- From: "Jim Davidson" < jdavidson @ davidsonassociates .net> To: sprinklerforum @lists. firesprinkler .org Sent: Friday, July 5, 2013 12:20:45 PM Subject: RE: POD Storage Michael, The following is the logic used in a project that we work with the Owner in addressing the AHJ concerns. THIS IS FOR YOUR REVIEW AND NOT FOR USE IN DESIGN, SINCE THIS IS AN ENGINEERING OPINION AND I AM NOT PROVIDING AN ENGINEERING OPINION IN MY RESPONSE TO YOUR QUESTION. The logic of looking at similar fuel load and fuel load configurations in NFPA 13 in order to apply to the PODS unit storage being contemplated is a common practice in the fire protection engineering community. Let us look first at the type of commodity being stored in the PODS unit. Discussion with other AHJ Fire Protection Engineers the commodity classification of the storage within the PODS units. The Fire Protection Engineer stated that he had opened and inspected a large number of the PODS units through out his jurisdiction and classifies the storage to be typical Class IV commodity. NFPA 13 Paragraph 2-2.3.4 defines a Class IV commodity as a product, with or without pallets, that meets one of the following criteria: (1) Constructed partially or totally of Group B plastics. (2) Consists of free-flowing Group A plastic materials. (3) Contains within itself or its packaging an appreciable amount (5 percent to 15 percent by weight or 5 percent to 25 percent by volume) of Group A plastics. The remaining materials shall be permitted to be metal, wood, paper, natural or synthetic fibers, or Group B or Group C plastics. The NFPA definition of a Class IV commodity describes almost all house hold products that could be stored in a PODS unit. Now that we have defined the type of commodity lets look at the height and storage configuration of the fuel load. The PODS unit is enclosed on five sides with ¾ inch plywood panels supported by 4" x 4" wood framing, approximately 8' wide x 8'-5" high x 16' long with a flexible plastic roof. A fire in a PODS unit will grow within the unit, when the roof of the unit is breached by the fire a large amount of heat and unburned products of combustion will be released into the building, which can result in a large column of superheated air racing to the ceil of the building. This large heat release from a shielded fire will overwhelm an ESFR sprinkler system by operating an excessive number of sprinkler heads. Each three high set of stored units with have a minimum 3 ft access aisle on all four sides of each stack of three high PODS units. To overcome the heat release from a shielded fire 286ºF temperature rated standard type of sprinkler will need to be used in the sprinkler system. Historically, this sprinkler head was used to address high heat release rated fires. A similar occupancy that has a shielded fire growth potential is the manufacturer of mobile /modular homes which is classified as an Extra Hazard Group II occupancy classification which is required to be protected by a sprinkler system designed to provide a design density of 0.40 gpm per sq. ft. over the hydraulically most remote 2,000 sq. ft. using 286ºF temperature rated sprinklers at the ceiling. A second design criterion is defined using the fire control approach for commodities stored on pallets, in solid piles or in bin boxes. The storage of Class IV commodity to a height of 25'-6" on pallets, in solid piles or in bin boxes required to be protected by a sprinkler system designed to provide a design density of 0.426 gpm per sq. ft. over the hydraulically most remote 2,000 sq. ft. using 286ºF temperature rated sprinklers at the ceiling. It appears that both design criterions are converging to a design density of 0.426 gpm per sq. ft. over the hydraulically most remote 2,000 sq. ft. as a single design point. Because of the storage of the PODS units three high there is a real possibility that a fire in a lower unit will cause the collapse of the pile onto a second pile of storage units and at the same time shield the fire from the water discharge from the overhead sprinkler system. In order to address the shielded fire issue from a collapse of a pile of three storage units a second sprinkler system density design criteria needs to be provided. Usually when there is a concern about a shielded fire the area of operation for the sprinkler system is increased to either 4,000 sq. ft. or even as high as 5,000 sq. ft. with a minimum design density of 0.30 gpm over the hydraulic most remote area. The design density of 0.30 gpm provides protection of the building's steel roof structure from the heat released from the shielded fire. We recommended a design criteria as to produce a sprinkler system density of 0.42 gpm per sq. ft. over the hydraulically most remote 3,000 sq. ft. and a secondary design density of 0.30 gpm per sq. ft. over the hydraulically most remote 4,000 sq. ft. A report was on how the design criteria was developed and sent to the AHJ for their review. This is an extremely condensed version of the engineering report sent to the Owner and AHJ. Have a fire safe day. Jim DAVIDSON ASSOCIATES Fire Protection Engineering P. O. Box 4010 Code Consultants Greenville , DE 19807-0010 Medical Gas Systems Engineering (302) 994-9500 Fax (302) 234-1781 CONFIDENTIALITY This report and any attachments are confidential and also may be privileged. If you are not the named recipient, or have otherwise received this report in error, please destroy the report, notify the sender immediately, and do not disclose its contents to any other person, use them for any purpose, or store or copy them in any medium. Thank you for your cooperation. -----Original Message----- From: sprinklerforum -bounces@lists. firesprinkler .org [ mailto : sprinklerforum -bounces@lists. firesprinkler .org] On Behalf Of Michael Foster Sent: Friday, July 05, 2013 2:46 PM To: sprinklerforum @lists. firesprinkler .org Subject: POD Storage We have a client that wishes to store the POD style storage units in their warehouse, they have asked what sprinkler design criteria is required. I have been unable to fine anything in NFPA or FM data sheet, so I am looking for any help Thanking you in advance Regards Michael Foster Phaser Fire Protection Ltd. mfoster @ phaserfire .ca < mailto : mfoster @ phaserfire .ca> tel: 604.888.0318 fax: 604.888.4732 cel : 604.790.0937 _______________________________________________ Sprinklerforum mailing list Sprinklerforum @lists. firesprinkler .org < mailto : Sprinklerforum @lists. firesprinkler .org> http ://lists. firesprinkler .org/ listinfo . cgi / sprinklerforum - firesprinkler .org < http ://lists. firesprinkler .org/ listinfo . cgi / sprinklerforum - firesprinkler .org> _______________________________________________ Sprinklerforum mailing list Sprinklerforum @lists. firesprinkler .org http ://lists. firesprinkler .org/ listinfo . cgi / sprinklerforum - firesprinkler .org _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
