>175 psi sprinkler system

[jimnogood]

Forum,

I am designing a combined sprinkler standpipe system with pressures in excess of 175 psi, but below 300 psi. As such, there will be pressure regulating valves on the hose connections to limit the static and residual pressures. I was planning on having PRV's on the sprinkler floor control valves as well, but I think I can do away with them if we use 300 psi rated sprinklers and piping.

I think any additional costs for the 300 psi components could be offset by deleting the PRV's. Although NFPA 13 mentions typical system pressures up to 175 psi, I don't believe it is a limiting requirement. Is there any reference in NFPA 13 for maximum system pressure? Aside from that, is there any safety, installation, or operational issues this might pose? Your thoughts would be appreciated. Thx.

 

[TravisMack]

I have done a few systems where we ran steel piping and 300 psi rated sprinklers. All of the standard pipe / fittings is already rated that high. The sprinklers were about $0.10 more per sprinkler. It was far cheaper to install the high pressure heads. Also, there is a long term savings of less maintenance since you don't have to test the sprinkler PRV every 5 years and waste the associated water.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[PEDARRIN2]

NFPA 14

7.2* Pressure Limitation. The maximum pressure at any point in the system at any time shall not exceed 350 psi (24 bar).


7.2.1 Maximum Pressure for Hose Connections.

7.2.1.1 Where the residual pressure at a 1 1/2 in. (40 mm) outlet on a hose connection exceeds 100 psi (6.9 bar), an approved pressure-regulating device shall be provided to limit the residual pressure at the flow required by Section 7.10 to 100 psi (6.9 bar).



7.2.1.2 Where the static pressure at a hose connection exceeds175 psi (12.1 bar), an approved pressure-regulating device shall be provided to limit static and residual pressures at the outlet of the hose connection to 100 psi (6.9 bar) for 1 1/2 in. (40 mm) hose connections and175 psi (12.1 bar) for other hose connections. The pressure on the inlet side of the pressure-regulating device shall not exceed the device's rated working pressure.

 

[jimnogood]

TravisMack,

Thanks, deleting the installation, set up and long term maintenance for the PRV's will definitely be a cost savings.

PEDARRIN2,

I agree with and will be complying with all the references that you've cited from NFPA 14. There will be PRV's on the hose connections. However, my question was regarding the sprinkler system. I do not believe that there is the same pressure limitations in NFPA 13. Do you concur?

 

[PEDARRIN2]

I agree that 13 does not limit the pressure below 175 psi that 14 does.

But you will have to install the PRV upstream of the valve. You will also have a test connection and drain for the PRV which can take up a lot of room since the drain must be a minimum of 3".

Take a look at the manufacturer's recommended installation of the PRV in a combined system - Tyco has one.

It shows the PRV upstream of the sprinkler floor control valve.

You may also want to talk to the fire department. They may not want more than 175 psi in the sprinkler system and may not approve the plans. It may cost a little bit more for the higher rated sprinklers.

You may have code on your side, but it is the fire department who reviews and buys off on your design. Often the code official follows the lead of the fire department.

Lets say you have 1000 sprinklers in your building - at $0.10 increase per head, that equates to $100 more in cost. It would cost you that much just going to an adjudication meeting to fight the fire department.

 

[jimnogood]

Thanks, PEDARRIN2. Great points, all!