Sprinkler per Branch line limit. 1

[AN1010]

Hi, Im new in sprinkler design system. Can anyone explain or clarify to me about the limit of sprinkler per branch line. nfpa 13 states:
23.5.3.1 Unless permitted by 23.5.3.2 or 23.5.3.3, branch
lines shall not exceed eight sprinklers on either side of a cross
main.
23.5.3.2 Where more than eight sprinklers on a branch line are
necessary, lines shall be permitted to be increased to nine sprinklers by making the two end lengths 1 in. (25.4 mm) and 11⁄4 in.
(33 mm), respectively, and the sizes thereafter standard.
23.5.3.3 Ten sprinklers shall be permitted to be placed on a
branch line, making the two end lengths 1 in. (25.4 mm) and
11⁄4 in. (33 mm), respectively, and feeding the tenth sprinkler
by a 21⁄2 in. (64 mm) pipe.
23.5.3.4 Pipe sizes shall be in accordance with Table 23.5.3.4.
23.5.3.5 Where the distance between sprinklers on the branch
line exceeds 12 ft (3.7 m) or the distance between the branch
lines exceeds 12 ft (3.7 m), the number of sprinklers for a given
pipe size shall be in accordance with Table 23.5.3.5.

Thank you.

 

[cdafd]

which edition of nfpa 13 are you looking at

 

[AN1010]

its 2013.

 

[cdafd]

My simple way is you are looking at a pipe scheduled system versus a hydraulicly calculated system.

https://www.usfa.fema.gov/downloads/pdf/coffee-break/cb_fp_2014_30.pdf

Basically someone can take the recipe and put a system together.


PIPE SCHEDULES FOR SPRINKLER SYSTEMS
In 1896, NFPA published the first fire sprin-
kler standard. Part of that standard prescribed the
piping installation schedule. The schedule identi-
fied the maximum number of sprinklers fed by a
given size pipe on a closed head system. In
1896, the first pipe schedule was the 1-2-4 sys-
tem. In this system, a 3⁄4-in. pipe could feed one sprinkler head, a 1-in. pipe could feed two sprin-
kler heads and a 1-1⁄4-in. pipe could feed four sprinkler heads. This was an early attempt to ensure that sprinkler parts were designed and installed in a method that sup- ported sound hydraulic principles of the era. When water flows through a pipe, friction loss reduces the available pressure in the system. By prescribing a maximum num- ber of sprinklers on a given size head, pressure losses were controlled.
In 1905, NFPA revised the pipe schedule system. The 1905 system was called the 1-2-3 pipe schedule system. Beginning with 1-1⁄4-in. pipe, the maximum number of sprinkler heads permitted was reduced. Overall, this schedule change improved the hydraulic performance of the sprinkler system.
Another major revision of the pipe schedule system occurred in 1940 when the sprinkler standard created a differentiation in the hazard of occupancy. Three occu- pancy hazard classifications were established, each with their own pipe schedule. Light-hazard occupancies pos- sess a lower rate of heat release and a lower combustible fuel loading. Typical light-hazard occupancies include office buildings, schools, hospitals and public assem- blies. Ordinary hazard occupancies were typical manu- facturing facilities, canneries, electronic plants, repair garages and wood product assembly facilities. Extra-haz- ard occupancies had a higher than normal combustible loading or had the presence of minor amounts of flam- mable liquids in the process. Special occupancies were beyond the scope of the sprinkler standard. High-piled or high-rack storage, tire storage, facilities with significant amounts of flammable liquids storage and use and other higher-hazard occupancies were protected in accordance with other standards. Occupancy classification was clas- sified in a subjective manner and generally focused on the expected heat release and amount of fuel in the occu- pancy. The 1940 standard created a major change in sprinkler system design and is the precursor to recogniz- ing that some occupancies require a more robust sprin- kler system, while lower-hazard occupancies are capable of controlling fires with lesser sprinkler discharge.
The 1940 standard eliminated the use of 3⁄4-in. pipe in sprinkler systems by introducing the 1940 2-3-5 pipe schedule system. The last two pipes on a line of sprin- klers were required to be at least 1 in. in diameter. Also, a light-hazard and an extra-hazard pipe schedule was introduced.
In 1953, a new pipe schedule was established. While there was no change to the extra-hazard pipe schedule, the ordinary-hazard pipe schedule introduced 8-in. pipe into the sprinkler system and allowed up to 400 heads on a single sprinkler riser, effectively allowing sprinkler sys- tems to be not greater than 52,000 sq ft in size, a limit that continues to exist today for light and ordinary haz- ard sprinkler systems. Prior to this, 6-in. risers and pipe were the largest identified, and sprinkler systems had 275 or less sprinkler heads. The greatest change was to the light-hazard pipe schedule. Hydraulic characteristics were improved by limiting the number of sprinkler heads allowed on pipes up to 31⁄2 in. diameter rather than 21⁄2 in. in the 1940 schedule.

 

[AN1010]

thank you for your reply cdafd.