Density/Area Curves Concept
The density/area curves have traditionally provided some flexibility in system pipe sizing. Under provisions of NFPA 13, meeting any point on the appropriate curve is acceptable. This permits the use of higher densities over smaller areas or lower densities over larger areas. Higher densities with smaller areas will generally result in larger branch-line piping but lower main sizes and lower overall water supply requirements. For this reason, a high-density, small-area point is often selected as the most economical.
minimum orifice sizes were specified for spray sprinklers protecting general storage, rack storage, rubber tire storage, roll paper storage, and baled cotton storage. For design densities of 0.34 gpm/ft2 (13.9 mm/min) or less, standard response sprinklers with a nominal orifice co efficient of K = 8.0 (Km = 115) or larger must be used. For design densities exceeding 0.34 gpm/ft2 (13.9 mm/min), standard- response sprinklers with a nominal orifice coefficient of K = 11.2 (Km = 160) or larger and that are specifically listed for storage applications must be used.
