Sprinklers in concealed spaces

[DSAFrank]

I see no mention of access to sprinklers in concealed spaces, although 26.1 states the system must be maintained. 8.1.2 is specific enough about valves and guages. Any comments?

 

[SprinklerDesigner2]

NFPA 25 - 2002 Edition
5.2.1.1.4* Sprinklers installed in concealed spaces such as above suspended ceilings shall not require inspection.

 

[NJ1]

Please do not confuse concealed spaces with accessible attics.

 

[SprinklerDesigner2]

For clarity let's assume the distance between each hydrant is 1,000 feet with the distance between hydrant "B" an hydrant "C" being 500' each direction.

For a flow test we are going to have 4 very accurate and calibrated gauges that read in one tenth of a pound increments.

For this flow test we will place a gauge on hydrant "A", "B", "C" and at the flange and spigot piece @ the proposed riser.

Assume all gauges are at the same elevation.

Static pressure is 100 psi and we should be reading 100 psi on all gauges.

Opening both 2 1/2" hose outlets we obtain a flow of 1,500 gpm and observe a residual pressure at Hydrant "A" of 64 psi.

1,500 gpm through 3,000 of 8" DR18 develops a friction loss of 40.8 psi or 0.014 psi/linear foot.

During the flow test we should expect the gauge at Hydrant "B" to read 50.4 psi, Hydrant "C" should read 36.8 psi.

We should expect to a reading of 43.6 psi at the gauge fixed to the flange and spigot piece which, since no water is flowing through the 6", means we have a residual pressure of 43.6 psi available at the 8"x6" tapping tee when flowing 1,500 gpm. To be clear the pressure at the tee would be 43.6 psi IF the elevation of the gauge you fixed to it was equal to the elevation of the gauges on the hydrants.

Carrying it down the pressure at hydrant "D" would be 23.2 psi and with this we can come up with the k-factor of the hydrant.

Single 2 1/2" hydrant butts on typical hydrants have a k-factor of between 140 and 150 but since we are flowing two buts it would be a lot lower.

For more fun let's analyze some elevation.

 

[SprinklerDesigner2]

I am sorry everyone, the post above was supposed to be in thread

http://www.eng-tips.com/viewthread.cfm?qid=274055&page=1