Closed Heads (Wet Type) Water Foam Sprinkler System with Ultra-wide proportioner

[Buildtech2]

There is one major difference between deluge and closed head system when using foam. With Deluge system, when the system operates, all all head receive foam solution. Only those heads actuated will receive foam solution on a closed head system.

In closed head system, a 4" ratio controller can be used so there must be a minimum flow before foam is generated. With each sprinkler head discharging approximately 16 gpm, at least 25 heads must open to ensure correct operation of foam system. This is a major disadvantage when using bladder tank with closed head foam sprinkler system.

A solution to this issue is to use an Ultra-wide proportioner instead of a ration flow propertioner. The Untra-wide proportioner will proportion correctly at a minimal flow of 20 gpm which is typically one sprinkler head discharging.

Now my question is as follows

1. Is Ultra-wide proportioner is expensive than ratio proportioner

2. Is it easily available in the market

3. Are are any operational and maintenance issues with it.

 

[skdesigner]

Ultra-wide ratio controllers are very useful when you're trying to proportion AR-AFF from a bladder tank with a closed-head system. Stuff is like molasses. NFPA 16 requires, among other things, that the proportioning system operates correctly with only the most remote four sprinklers flowing for closed head systems.

To answer your questions:

1 - yes

2 - no more difficult to procure than any other foam system components

3 - Not that I've encountered

 

[Buildtech2]

Thanks skdesigner.

If we are using closed head sprinklers, AHJ will require an application area more than 0.16 gpm/sft. Therefore, I am planning to use foam density as 0.3 gpm/sft for foam calculations. Lower density with water will result in smaller pump and tank, can I use water density as 0.16 gpm/sft with this application.

 

[LCREP]

What are you trying to protect? The protection is based on the occupancy not just some number you pick.

 

[Buildtech2]

You are quite right LCREP.

This is a chemical warehouse where hazardous and flammable chemicals will be stored in a racking system which is around 5 m and warehouse height is 6.5 m.

 

[LCREP]

OK so what standard are you using and what is your design based on the standard. In the USA we would use NFPA 30 or FM Data Sheet 7-29.

 

[Buildtech2]

We also use NFPA 30 here for this application.

Since sprinkler system is also serving to the tire storage along with chemical warehouse, as per occupancy classification, it can be classified as an ordinary hazard, group-2 (Tire storage & Chemical plant-ordinary)(please verify).

Based on commodity classification, it can be classified as Group B commodity mainly due to the tire storage in an adjacent small storage room.

In rack sprinklers will not be provided as warehouse height is only 7.5 m.

 

[LCREP]

Buildtech2

It appears we are in the same place as we were a few weeks ago...

http://www.eng-tips.com/viewthread.cfm?qid=420936

Have you reached out to a fire protection professional yet??

 

[Buildtech2]

You are quite right LCREP. Now our client is directly dealing with the firefighting specialist for designing as water foam sprinkler system is a pre-engineered system to be designed and installed by the specialsit but I am doing some background study as final design package will come back to me for the final review.