American Fire Sprinkler Association [http://www.firesprinkler.org/] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
AFSA Technical Update ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ A newsletter dealing with codes and other technical issues September 27, 2013 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Grouped Obstructions "I have a store with a rack of mechanical piping that is at 13 ft above the finished floor with 200 degree standard spray upright sprinklers at the 18 ft - 4 in. elevation. The conduit rack is 3 in. or less piping with 1 in. gaps attached to Unistrut. The width is 12 ft with a linear run of 80 ft. The fire inspector is requesting a row of sprinklers under the conduit raceway, the occupancy is over a break room with no ceiling, and supermarket retail with storage 8 ft or less. Is protection under the conduit raceway necessary?" We have reviewed NFPA 13, 2013 edition as the applicable standard. Our informal interpretation is that NFPA does not provide specific guidance on grouped obstructions. There is no guidance on how to address grouped items for any of the sprinkler types within NFPA 13 except for the existing obstruction rules. The committee did address a comment for grouped obstructions during the 2009 Report on Comments in 13-119 Log #234 with an action of Reject. The submitter proposed a new Section 8.5.5.3.3.4 that stated, "Grouped Obstructions. Closely spaced obstructions shall be considered a single obstruction when the space between individual obstructions is smaller than the width of the smaller adjacent obstruction. A.8.5.5.3.3.4 When there are more than two adjacent obstructions, the width of the "grouped obstruction" is intended to include any additional obstructions that do not meet the separation requirement." The committee rejected this proposal since insufficient material to inform a Committee Action on this item. This leaves us with the existing obstruction rules in NFPA 13. If standard spray sprinklers are used and the grouped obstructions are located more than 18 in. down from the deflector, the grouped items with spaces in between can be ignored (unless they appear as a solid obstruction). Standard spray sprinklers are fairly tolerant of obstructions. The sprinkler has the ability to get water on both sides of the obstruction without allowing a significant dry shadow on the other side of the obstruction. This works for continuous and isolated obstructions where the sprinkler can throw water over and under the obstruction. This keeps the upper layer gases in the room cool, thus prevents flashover, and controls the fire. If the obstruction is within 18 in. between the grouped obstruction and the deflector, the three times rule or beam rule would be applied as applicable. FM Global does address this differently. It defines grouped object obstructions in Data Sheet 2-0 dated April 2011. This states, "Grouped Object (obstruction): Two or more adjacent objects are considered a grouped object for obstruction purposes when the horizontal distance between them is less than 3 times the object's least dimension. Under these conditions the width of the object, for obstruction evaluation purposes, is considered the width of both objects' least dimensions plus the horizontal distance between them. An example of a grouped object would be a 3-in. wide service pipe that is located 8 in. away from another 3-in. wide service pipe. Collectively, they represent a 14-in. wide object for obstruction analysis purposes." Rules are then applied for object obstructions within the data sheet for storage and nonstorage sprinklers. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ firesprinkler.org [http://r20.rs6.net/tn.jsp?e=0019Hk9DtkwqM3bXC6TVutzm6Ex0I4Oevyqb33FBMtbKjQeXp1kHmpFx7CcjHzwlTKYdJhxs80XzXh_Xl2xLtpxnZGnbZBNM88hUzk1B2iT2G4amk9z6E3h4J4cyIvB-0Jp] Hosted by the American Fire Sprinkler Association ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Technical Update is prepared by the Technical Services Dept. of the AFSA: Vice President of Engineering and Technical Services Roland Huggins, a PE registered in fire protection engineering; Phill Brown, a NICET IV certified automatic sprinkler technician and NFPA Certified Fire Protection Specialist (CFPS) and Tom Wellen, a PE registered in fire protection engineering. This is provided with the understanding that the AFSA assumes no liability for this opinion or actions taken on it and they are not to be considered the official position of the NFPA or its technical committees. Copyright 2012, American Fire Sprinkler Association. All Rights Reserved ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PDF Version PDF Link [http://r20.rs6.net/tn.jsp?e=0019Hk9DtkwqM2BNfRJdWv-jZJGUrutkXc_18ofWzySoFo2gYIQF1iYfqFqaQbRdeL07UyEHW8hF86lseme9LXQNhzatMp_Q1Inp_SZqGJq-p-LtXU9j87RFYHue764IakemuwqUmhNfMNSd29B4y-deIqSJiaRNuDTMlthdQRtq2ckg8k1TWlIjcJM7RGIRZM_KrnOH4THcTy26eTLEJiYfQ==] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Training Calendar AFSA Beginning Fire Sprinkler System Planning School Oct. 28 - Nov. 8, 2013 Check our calendar to view upcoming training. 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