FPE Corner Continued from page 24
strainers. Note that strainers are required on all Factory Mutual systems. Pumps used in water mist systems must comply with NFPA 20. Nozzles that are available as open head or closed head
type must be listed, either individually as a component or as part of a system. Nozzles are listed by one of the following standards: • FM Approval Standard 5560, Water Mist Systems • UL2167, Water Mist Nozzles for Fire-Protection Service • IMO 800 (19), Revised Guidelines for Approval of Sprinkler Systems Equivalent to that Referred to in SOLAS Regulation II-2/12 NFPA 750 requires the nozzle listing to include the fol-
lowing information: • Specific hazards and protection objectives • Volumetric flow rate characteristics of water discharge
for each nozzle • Maximum height of protected space • Minimum distance between nozzle tip or diffuser, as applicable, and plane of protection • Maximum and minimum spacing between nozzles • Maximum coverage area per nozzle • Maximum height between ceiling and nozzle diffuser or
tip, as applicable • Nozzle obstruction spacing criteria • Maximum spacing of nozzles from walls • Minimum- and maximum-rated operating pressures of 9:16 PM
nozzles • Allowable range of nozzle orientation angle from verti-
cally down • Classification of automatic nozzle thermal response characteristics as fast, special or standard response • Maximum compartment volume, if applicable • Maximum time delay for water mist delivery to the most
remote nozzle The Design. The current state-of-the-art in water mist fire protection system design is that there is no comprehensive set of guidelines that can be used to engineer a system, such as we are able to do for sprinkler systems using NFPA 13. Therefore, unless you are bold and like to go where no per- son has gone before, you are constrained with protecting hazards that fit into the limited number of approved pre- engineered system designs. More on that next month. n
Samuel S. Dannaway, PE, is a registered fire protection engi-
neer 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.
The views and opinions expressed in this column are those of the author and do not reflect those of Plumbing Engineer nor its publisher, TMB Publishing.
Circle 16 on Reader Reply form on page 73 Page 26/Plumbing Engineer October 2011
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