hose stream allowance

[BSSTG]

Greetings all,

I'm new to this but there is something that does not make a lot of sense to me on a set of sprinkler dwgs submitted. Why is it that a "hose stream allowance" is provided for in the hydraulic calculations when there is no standpipe in the bldg nor is one required?

thanksabunch

BSSTG

 

[cda]

Accounting for hose stream allowances

Sprinkler hydraulic calculations are required to account for the water used by the fire department to manually suppress a fire. This is referred to as a hose stream allowance. Typically this is shown on a hydraulic graph as a line of a length equal to the allowance (in gpm) and extending horizontally from the maximum sprinkler demand. The problem with this depiction of the total system demand versus the supply is that the hose streams are not flowing at the maximum pressure demand of the sprinklers and not just at flows higher than the maximum sprinkler demand.

In reality, the fire department is “taking this amount of water away” from the available supply and the sprinkler system is “left” with a degraded water supply curve. This concept has been developed and promoted by J. Michael (Mike) Thompson, P.E.; a founding partner of the Protection Engineering Group. Mike has developed software providing a number of hydraulic tools, one of which plots supply vs demand curves in this fashion.

http://www.plumbingengineer.com/may_11/sprinkler_feature.ph

http://www.usfa.fema.gov/downloads/pdf/coffee-break/cb-2006-50.pdf

 

[Markmax33]

Yes. An outside hose stream demand would be required in accordance with Section 11.2.3.1.1 in NFPA 13. This is to allow the fire department to pump up the system with the onboard fire pump if there are a bunch of fire sprinklers operating as CDA said.

 

[Builder Bob]

Not all sprinkler systems are designed to put the fire out, they are designed to hold the fire in check so that the fire department can perform fire suppression and/or salvage and overhaul..... High Piled Storage is a good example where a sprinkler system is designed to slow down or hold a fire in check.........