Water Foam Sprinkler System

[Buildtech2]

In chemical warehouse where hazardous chemicals will be stored in a racking system.The warehouse height is 7.5 m and total area is 2025 sqm. As per MSDS sheets, water foam sprinkler system to be used but this facility can be classified as Extra hazard, group-1 as per NFPA. As per manufacturers instructions and NFPA 16, the k factor shall be 3.0 gpm/psi (Tyco Model B-1) with minimum discharge pressure not less than 30 psi and I believe that water foam density shall be 0.16 gpm/sqft for the foam system. Now my question is as follows.

What density to be considered in hydraulic calculations?
If I use density as 0.16 gpm/sqft,I cannot use 2500 sqft as sprinkler area of operation and 100 sqft as sprinkler area coverage. In order to consider this facility as an extra hazard, I must use 0.3 gpm/sqft and 100 sqft as sprinkler coverage area.

It would be highly appreciated if anybody can guide me on this.

 

[LCREP]

See NFPA 30 or FM Data Sheet 7-29 for foam sprinkler density design requirements.

 

[Buildtech2]

Noted LCREP

My main problem is the common pump to be used for the chemical warehouse with water foam system and also for other workshops with only water sprinkler system and these workshops were classified as Ordinary hazard, group-2. So I have to select the density which can match both the chemical warehouse with foam system and also for the workshops with only water sprinklers.

 

[LCREP]

Can you use a separate riser for the foam systems? Is the water supply and fire pump sized to meet the largest sprinkler demand?

 

[Buildtech2]

Yes, there are separate risers for the foam sprinklers and normal water sprinklers. There is a confusion in the calculations as I have to find the correct density to calculate the required pumping flow rate.

 

[LCREP]

Use the references I gave you to determine the requirements for the sprinkler system design based on the following:
floor or rack storage,
height of storage,
type of rack single, double,
container size,
relieving or nonrelieving drum
container material plastic, metal, etc.

Use the msds sheet to determine the flammable or combustible data to determine the classification of the material based on the reference standard used such as class 1A, 1B etc flammable liquid. Extra hazard system is not for the storage of flammable or combustible liquid other than misc. storage.

Consult with a fire protection professional and also reach out the the engineering department of the property insurance carrier for feedback.

 

[Buildtech2]

Thanks LCREP

For Deluge water foam sprinkler system, do we follow the same procedure of hydraulic calculations in terms of density and sprinkler area of operation and sprinkler coverage.

 

[LCREP]

Typically a deluge system is not used to protect a chemical warehouse because of water damage. A closed head foam or water only system is used. Foam is used most times because NFPA 30 requires a drainage system to carry away the water to prevent the flaming liquid burning on top of the water from spreading the fire.

 

[Buildtech2]

LCREP

Thanks LCREP, I am pleased to hear that only water system can be used for the chemical warehouse but MSDS sheets suggest to use any one of the following systems for the type of chemicals to be stored.

Water fog system
Foam system
dry chemical
CO2

I have selected foam system. If I can use only water, it would be really great. Please let me know the feasibility of using only water sprinklers.

 

[LCREP]

Refer to NFPA 30 or FM Data Sheet 7-29 as I stated above. The storage of "chemicals" is a complex subject and it appears you need professional help more than we can give via this forum.

 

[Buildtech2]

Noted LCREP

Many thanks for your advise