Pressure at hose valve 2

[orator]

A building (Group A) is provided with automatic sprinkler system. Standpipe is not required as the distance lowest level of fire department access and highest floor level is less than 9.1 m (building is 2 story). As there is no standpipe, if I provide a hose connection (fire hose cabinet) considering the hose stream allowance from NFPA 13 what will be the pressure required at this hose connection. This hose is not a part of standpipe therefore I think 4.5 bar is not required. Please give any NFPA references.

 

[skdesigner]

NFPA 13-2010 11.1.6.5 Where inside hose connections are planned or required, the following shall apply:

(1)A total water allowance of 50 gpm (189 L/min) for a
single hose connection installation shall be added to the
sprinkler requirements.

(2)A total water allowance of 100 gpm (379 L/min) for a
multiple hose connection installation shall be added to
the sprinkler requirements.

(3) The water allowance shall be added in 50 gpm (189 L/min)
increments beginning at the most remote hose connection,
with each increment added at the pressure required by the
sprinkler system design at that point.

As you are calc'ing your system, drop a node at the hose valve(s), and add a q of 50 gpm at that(those) point(s). Whatever the pressure happens to be at that point in the system, is what pressure is required at the hose valve.

 

[PEDARRIN2]

skdesigner,

I do not know it is that simple.

If this is light hazard, then the sprinkler flow would be 0.1 gpm/sf, measured over 1500 sf. This would give you 150 gpm for the sprinkler load. Adding 50 gpm would give you 200 gpm. Minimum pressure for sprinklers is typically 7 psig. So the water supply would have to be able to provide 200 gpm and overcome whatever pressure drop which would result in 7 psig at the most remote sprinklers.

If the hose valve is at around 4' off the floor and the sprinklers are at 10' off the floor, you gain ~2.6 psig back - so the minimum pressure at the hose valve would be ~9.6 psig. Depending on where the hose is at in the system, you will gain back whatever pipe friction lost flowing to the sprinkler. But even if it was 10 psig, would ~20 psig be enough to flow through a hose connected to the hose connection?

If this is a commercial building with a fire department pumper connection, I do not know if you need to know the pressure at the fire hose connection. The fire department will provide the pressure with their equipment.

If there is not a fire department connection, I would likely fall back on 4.5 bars which NFPA 14 requires for a Class II standpipe (1.5" hose).

 

[3cio]

hi!

I think if the system is to be provided with centrifugal fire pump, it should be more than 40psi as per NFPA-20 clause 4.8.2.

As per AHJ requirement in my previous project, they are always requiring class II system in every building as a first line of defense. Tjen, 4.5bar is required.


hope it helps,