At present, there is no method of predicting the actual amount of water that will be delivered to a specific unit of floor area under actual fire conditions, especially since spray patterns vary with water discharge pressures
Figure 16.1.6 demonstrates the variability of the spray pattern of a typical pendent spray sprinkler with a nominal orifice coefficient of K = 5.6 (Km = 80) when discharged under non fire conditions at selected pressures. A 7 psi (0.5 bar) operating pressure is considered minimum by NFPA 13 , At that minimum pressure, the extent of the spray pattern roughly approximates that of the maximum light hazard spacing permitted by NFPA 13, when the sprinkler is located 8 ft (2.4 m) above the floor. The spray pattern enlarges as the operating pressure is increased to about 70 psi (4.8 bar), then begins to contract at higher pressures, becoming more elliptical in shape at the upper end of the allowable pressure range.
