Dewayne, And Joe, please elaborate at your convenience as I know you have far more background knowledge in this arena than I.
FM Data Sheet 2-2, Section 2.4.5.3.2 gives (what I believe to be) pretty sufficient guidance in addressing your situation. Specifically Item-4 "If the obstructions below sprinklers is not continuous circular or rectangular (such as a light) with a maximum dimension of 24" in., locate the sprinkler deflector at least 12" horizontally from the nearest edge of the obstuction." It seems to me a plumbing stack, rain leader, vertical exhaust duct etc. could be treated the same, based on its size and per its obstruction rules, whether it was vertical or horizontal. It also seems to me a vertical obstruction affecting one sprinkler would be less of a problem than the same obstruction placed horizontal affecting more than one sprinkler if you place the sprinklers according to the obstruction rules for the size of your obstruction and the required distance of the sprinklers away from the obstruction. Yet we have specific guidance for the horizontal obstructions and not the vertical ones. Hmmmm! If the obstruction rules work for the horizontal obstructions, why would they not also work for the vertical? (I know the full development of the spray pattern and getting the correct amount of water thru the fire plume to the base of the fire is critical even for one sprinkler activating. It just seems to me that the considerations would be much the same with the obstruction in either plane.) In closing, I would make the suggestion that spacing your sprinklers from the vertical obstruction exactly as you would the horizontal would give some level of confidence in maintaining the suppression mode of the ESFR sprinklers. We do not typically consider 6", 8", 10" vertical structural columns (square, round, or otherwise) as obstructions. Of course we are usually more than 2ft away from them :-) Thanks, Ray Vance Chief Engineering Tech. Wayne Automatic Fire Sprinklers, Inc. www.waynefire.com -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Dewayne Martinez Sent: Wednesday, February 07, 2007 9:01 AM To: [email protected] Subject: RE: ESFR AND VERTICAL OBSTRUCTIONS (NFPA 13 07ed) So I take it that you have never installed ESFR sprinklers in a building that included roof drains that run from the roof deck to the floor along a column? -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Joe Hankins Sent: Wednesday, February 07, 2007 7:51 AM To: [email protected] Subject: Re: ESFR AND VERTICAL OBSTRUCTIONS (NFPA 13 07ed) Dewayne, If it is impractical, then don't install ESFR's. There are other alternatives (e.g. in-rack sprinklers). ESFRs are an option only if their installation rules are met. ESFR's are asked to do a lot more than any other sprinkler. As a result, there is no margin for error when it comes to obstructions. If there is a single obstruction and the fire starts in the wrong spot, then failure to suppress or control is a very real possibility. In the testing of ESFR sprinklers, the scenario of a fire starting centered between two sprinklers with one of them obstructed resulted in a barely controlled fire in a 30 ft. building (11 sprinklers operated) and uncontrolled fire in a 40 ft. building. Joe Dewayne Martinez wrote: >I am looking for some input from the forum on how you treat a isolated >vertical obstruction that restricts only one ESFR sprinkler head. It >is both above and below the sprinkler. Such as a round exhaust duct >from a unit heater below up through the deck or a plumber drain stack? >An informal request to NFPA resulted in this response "Section >8.12.5.2(5) allows sprinklers with special obstruction allowance shall >be installed in accordance with its listing. ESFR sprinklers have very >particular obstruction criteria, and interpolation, or modification of >obstruction rules is not allowed." I have yet to find a ESFR sprinkler >to address this issue, in the past I have followed the rules for >isolated obstructions below the sprinkler to provide guidance. It >seems impractical to expect a storage building to be constructed >without any vertical obstructions. > >Thanks, >Dewayne Martinez >Design Build Fire Protection >[EMAIL PROTECTED] >_______________________________________________ >Sprinklerforum mailing list >[email protected] >http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum > > > _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum Wayne Automatic Fire Sprinklers, Inc. 2006 Inductee into "The Players Hall of Fame" at The Great Games of Business Wayne Automatic Fire Sprinklers, Inc. 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