How to control downstream pressure/flow of deluge valve?

[akupikree]

Hi all,

Im doing the static hydraulic calculation for sprinkler firewater system on offshore platform.

I need to kill the flow/pressure that going into the sprinkler system (downstream of deluge valve) after deluge valve is opened. However the valve cannot kill the pressure/flow as required. I cannot change the pipe size due to velocity limitation.

I need to kill the pressure up to 4 bar (58 psi) and restriction orifice is not allowed. is it possible?

Thanks in advance!

 

[b1ueshift]

I'm not sure kill is the right verb here.

Why do you need to reduce the pressure to 4 bar?

 

[akupikree]

I want to restrict the flow. My client dont want the flow passing through the deluge valve exceeds 1000m3/hr due to dificulty in reaching steady state condition. Currently, the flow is at about 1200 m3/hr. Im just curious what people normally do when facing something like this.

Btw, 4 bar that I mentioned is pressure drop not the d/s pressure.

Thanks!

 

[TravisMack]

Since velocity requirements are not in NFPA, but will appear in specs due to unfamiliarity with the specifying engineer. I have also seen insurance underwriters limit velocity. You may be able to talk with them about exceeding velocity limits on this project due to your needs.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[b1ueshift]

An orifice would be the cheapest and easiest way of doing that and probably also the best way.

If you can't use an orifice, I don't think you'll find a better solution.

 

[chillylulu]

Man, I hit the back button twice after replying and lost my post. Now I am copying this from Word.

The amount of water that Akupikree is referring to is more than most sprinkler designers deal with. He needs to reduce the flow from 5,280 GPM to 4,400 gpm. The velocity on a deluge system of this size is important when filling, not from a calculation standpoint. The reason is to avoid water hammer.

I assume from earlier posts that the pressure that we are dealing with is 190 PSI @ 5280 gpm and the need is to reduce the pressure to 132 PSI @ 4400 gpm.

Can you use a pressure reducing valve upstream of the deluge valve? If it is a true deluge system, and the pressure reducing valve is located close to the deluge valve (I would generally put it right before a strainer) you should also have a small (3/4”) pressure relief valve below the deluge valve. If you are using cla-valve deluge valves, use the same valve configured as a pressure reducing valve. That reduces the number of different valves and or repair parts to deal with.

 

[Pumpsonly]

Take a look at this..

http://www.inbalvalves.com/english/s_pressure.htm