I'm good. Let me throw out there perhaps the committee consider removing the 1 heads vs. 2 or more criteria and turn it into a weight or length issue. I see where the committee could assume 10' armovers being a typical practical limit but one, there are many strange things in the real world and two, a three head 4' branchline is probably better than a 10' armover. I'd consider a code change amendment but being unwashed and all....
Chris Cahill, PE* Senior Fire Protection Engineer Burns & McDonnell 8201 Norman Center Drive Bloomington, MN 55437 Phone: 952.656.3652 Fax: 952.229.2923 [email protected] www.burnsmcd.com Proud to be one of FORTUNE's 100 Best Companies to Work For *Registered in: MN -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Mark A. Sornsin, P.E. Sent: Tuesday, October 22, 2013 11:40 AM To: [email protected] Subject: RE: NFPA 13 '10 9.3.6 BL Restraint Tom, Thank-you for your thoughtful and insightful reply. It addressed our question and, therefore, should be a model for all of the Forum - especially Steve and Ken. Bottom line is, yes, there are 8 ft. arm-overs that would not require restraint to meet seismic requirements; and there are 8 ft. branch lines feeding two sprinklers that would require restraint. It seems to be a bit of a cross-over in the rules, but ultimately doesn't happen much and thus isn't considered to be a real problem. I can't speak for Chris (despite having done so before), but I feel satiated. Mark A. Sornsin, P.E. | Karges-Faulconbridge, Inc. | Fire Protection Engineer | Fargo, ND | direct: 701.552.9905 | mobile: 701.371.5759 | http://www.kfiengineers.com -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Tom Wellen Sent: Tuesday, October 22, 2013 10:00 AM To: [email protected] Subject: Re: NFPA 13 '10 9.3.6 BL Restraint Mark and Chris, I'll take a stab at this. The west coast is still grinding the coffee beans. The length of an armorer is not expected to be very long. The adjacent branch lines cannot exceed 20 feet apart for extended coverage sprinklers and 15 ft for standard spray sprinklers. If the armorer is over 10 ft long coming off a cross main or branch line, it should be considered to be piped from the adjacent branch line. The main objective is to use less pipe, correct? Why waste pipe length? So, if that is the case, the committee is not worried about a line with a single sprinkler and provided the definition of an armover. A line with two or more sprinklers is defined as a branch line where they can be of considerable length. The longer the line, the more it will have a whipping action. Thus, Table 9.6.3.4(a) specifies the spacing needed for restraints based on the Cp in that area and the pipe size ranging from 26 ft to 53 ft. An armorer shouldn't whip around so much due to its short length so restraint is not required. Can there be instances where there are long armorers? Sure, especially if there is a drop from a 40 ft ceiling to a ceiling at an 8 ft level. 9.3.6.7 Drops and armorers shall not require restraint. What a mess that would be to restrain a drop located 32 ft from the ceiling. Steve commented that ceiling grids should be rigidly braced. If not, then the oversized hole for the sprinkler is necessary in the ceiling to keep the ceiling from bre aking the fusible element. Will fusible elements still still break during an earthquake from the ceiling? Probably. The cost benefit of providing restraints on every drop does not warrant them to be installed. NFPA 13 is full "lines in the sand" that we don't know the true history behind them but it seems mostly just to give a warm fuzzy (i.e. 4 ft obstruction rule, area limitations of 52,000 sf, etc....) and armorers and branch lines is just one of them. It doesn't fit all applications, but the baseline requirement is established. Tom Wellen AFSA _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
