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NOTE: This is an unformatted excerpt from our online fire protection training library.

Hydraulic Calculations

Density/Area Method

Applying the Curves

A number of rules are outlined in NFPA 13 when applying the density/area curves, and they will modify the selected design.
The design curves used in NFPA 13 only apply when using spray sprinklersSpecial sprinklers, such as window or exposure sprinklers, can not use these allowances, nor do they use these curves. These types of special sprinklers have their own sets of rules for installation and location, depending on the specific sprinkler.. Quick response sprinklers
are required to be used in light hazard occupancies
can be used in ordinary hazard occupancies, unless there is a dust or flammable liquid hazard present can't be used in extra hazard occupancies If quick response sprinklers are used, the area of operation can be reduced without revising the density, provided all of the following are met:  the system is wet pipe Quick response sprinklers can't be used on dry pipe systems, unless they are specifically listed for that application.,
the hazard classification is light or ordinary,
the ceiling doesn't exceed twenty (20) feet, and there are no unprotected ceiling pockets. If extended coverage sprinklersExtended coverage sprinklers can be spaced at 400 sq. ft. per sprinkler. Thus, if an area of application of 1,500 sq. ft. is chosen, it only encompasses four (4) sprinklers to meet the parameters of the area of application. This is not allowed because of the large allowable spacing - if one head is blocked or obstructed, too much of the area of application is without coverage. are used, a minimum of five (5) sprinklers must be calculated, regardless of the area of application chosen. The area of operation for spray sprinklers must be adjusted if any of the following situations exist: An increase in area of operation of 30% is required for a sloped roof of a pitch greater than one (1) in six (6)This is a slope of 16.7%.. An increase in area of operation of 30% is required for systems that are dry pipe or double interlock preactionThese systems have an operational delay built in because of the way they function. Thus, a larger fire is anticipated while the delay in activation is overcome.. A decrease in area of operation of 25% is allowed for high temperatureOrdinary temperature sprinklers are in a range of 135 to 170 degrees F, and intermediate sprinklers are 175 to 225 degrees F. High temperature sprinklers are in a range from 250 to 300 degrees F, with the most common one being a 286-degree sprinkler. sprinklers installed in high hazard locations, but the area of operation can never be reduced below 2,000 sq. ft. These adjustments are compounded, based on the area of operation originally selected.  
NOTE: This is an unformatted excerpt from our online fire protection training library.

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