Fire sprinkler system pressures

[dinkelja]

What is the propper pressure to pump into the FDC sprinkler system. I thought it was constant, regardless of building size, assuming the inlet would be sized appropriately to maintain estimated flow rates. So if the building has a standpipe, what is the minimum working pressure that must be maintained at the top floor? (I am working on getting copies of NFPA 13, 20, 25) What are some of the other usefull articles? Thanks for any help with these broad questions. (I am an electrical engineer). Jared, Cincinnati, OH, USA

 

[TravisMack]

For the standpipe, you are required to have 100 psi at the top most outlet at the required flows. I believe that most sprinkler designers go with 150 psi available at the FDC when sizing the standpipe system. This is for manual wet or dry standpipes. Once your floor highest floor level is >75', then you fall under a high rise building and the water supply shall be capable of supplying 100 psi at the top outlet at the required flows. This will almost always guarantee a fire pump is on the project.

 

[ChrisConley]

You should also look at picking up NFPA 14, which is standpipe design.

 

[cdafd]

http://www.fmglobalcatalog.com/ProductInfo.aspx?productid=P8708

I have had this cd for awhile but have not looked at it. It may answer some of your questions and is free if you are a gov agency or fm customer, or you could ask a firefighter to order it for you

 

[LCREP]

Another good document

http://www.osha.gov/Publications/fire_features3256.pdf

 

[SprinklerDesigner2]

I worked in Ohi for years and unless they changed, which I doubt they have, Ohio does not allow "dry standpipes". By "dry" I am talking about standpipes that obtain their source of water only fire fire department pumper trucks.

With few exceptions, one being in the valley outside of Akron where I had a water flow test yield a static pressure of 240 psi, a residual of 230 psi and the 2 1/2" flow pegged my pitot out at 100 psi, if you need a standpipe in Ohio you will have a fire pump. Oh, and pressures above 200 psi like I got are extremely rare.

It was for a nursing home and the only job I ever did where I had to use a pressure reducer but was my pipe ever small. 2" riser and 1" branch lines.

Anyway, From NFPA #14

5-7* Minimum Pressure for System Design and Sizing of Pipe.
Standpipe systems shall be designed so that the system demand can be supplied by both the attached water supply, where required, and fire department connections. The authority having jurisdiction shall be consulted regarding the water supply available from a fire department pumper.
Standpipe systems shall be one of the following:
(1) Hydraulically designed to provide the required waterflow rate at a minimum residual pressure of 100 psi (6.9 bar) at the outlet of the hydraulically most remote 21/2-in. (63.5-mm) hose connection and 65 psi (4.5 bar) at the outlet of the hydraulically most remote 11/2-in. (38.1-mm) hose station.
Exception No. 1: Where the authority having jurisdiction permits pressures lower than 100 psi (6.9 bar) for 21/2-in. (63.5-mm) hose connections, based on suppression tactics, the pressure shall be permitted to be reduced to not less than 65 psi (4.5 bar).
Exception No. 2: In other than high-rise buildings, the authority having jurisdiction shall be allowed to reduce the minimum pressure requirements of this section if the building is protected throughout by an approved automatic sprinkler system.

5-9.1 Class I and Class III Systems.
5-9.1.1* Minimum Flow Rate.
For Class I and Class III systems, the minimum flow rate for the hydraulically most remote standpipe shall be 500 gpm (1893 L/min). The minimum flow rate for additional standpipes shall be 250 gpm (946 L/min) per standpipe, with the total not to exceed 1250 gpm (4731 L/min). For combined systems, see 5-9.1.3.
Exception: When the floor area exceeds 80,000 ft2 (7432 m2), the second most remote standpipe shall be designed to accommodate 500 gpm (1893 L/min).

For what it is worth I never had a problem getting the local fire official to accept 65 psi at the top outlet per Exception #2. In Ohio all you need was to produce a letter from the fire official to present to the building official and it flew through.

Also, in Ohio, all standpipes are hydraulically calculated to the water supply available.