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Properly designed hydraulically designed sprinkler systems will discharge a measurable amount of water ("density") onto a defined floor spaceThe defined floor space, the "area of application", is the hydraulically worst area of the building. In other words, it is the area that represents the hardest part of the building's sprinkler system to flow water to...it represents the most required flow, and the most required pressure. ("area of application" or "area of sprinkler operation"). The discharge density is the amount of water that is required to "control" a fire, and the area of application is the size of the space over which the discharge density is provided, and in which control can be expected.

Let's apply some numbers to the design, such as 0.25 gallons per minute (gpm) per square foot (sq. ft.) over the most hydraulically remote 3,000 sq. ft. area. To determine if the system is capable of this amount of discharge, we can use some very simple measurementIt isn't likely that this method will ever be used, but it is as simple as this...calculations will be used to verify this design, rather than the 3,000 buckets!! techniques. We'll use 3,000 square buckets that are exactly one (1) sq. ft. at the bottom. We will place them side by side in the most hydraulically remote area of the building. Then, we'll open all of the sprinkler heads in that most hydraulically remote area. If we let the water run from all of the heads simultaneously for a minute, each bucket in that 3,000 sq. ft. area would contain a quarter of a gallon (0.25) at the end of the first minute.

The numbers that the designer chooses for the sprinkler system discharge are conceived through testing, and reflected in tables and figures in NFPA 13. They are based on the heat release characteristics of the occupancy in the space that the designer is considering.

The hydraulic calculations for ESFR and special application systems are calculated differently, as you will see later in this course. But, the calculations include providing for a specific amount of flow from each nozzle, over the most hydraulically remote area of the building, which represents the worst fire area.

Let's apply some numbers to the design, such as 0.25 gallons per minute (gpm) per square foot (sq. ft.) over the most hydraulically remote 3,000 sq. ft. area. To determine if the system is capable of this amount of discharge, we can use some very simple measurementIt isn't likely that this method will ever be used, but it is as simple as this...calculations will be used to verify this design, rather than the 3,000 buckets!! techniques. We'll use 3,000 square buckets that are exactly one (1) sq. ft. at the bottom. We will place them side by side in the most hydraulically remote area of the building. Then, we'll open all of the sprinkler heads in that most hydraulically remote area. If we let the water run from all of the heads simultaneously for a minute, each bucket in that 3,000 sq. ft. area would contain a quarter of a gallon (0.25) at the end of the first minute.

The numbers that the designer chooses for the sprinkler system discharge are conceived through testing, and reflected in tables and figures in NFPA 13. They are based on the heat release characteristics of the occupancy in the space that the designer is considering.

The hydraulic calculations for ESFR and special application systems are calculated differently, as you will see later in this course. But, the calculations include providing for a specific amount of flow from each nozzle, over the most hydraulically remote area of the building, which represents the worst fire area.

© Hughes Associates,Inc. 2012