Foam Design Criteria for Diesel Storage Tank?

11/8/2023

We have a project design for a single room (26'-0" x 14'-6", height of 13'-2"). The room is noncombustible and is solely for the storage of one large metal diesel fuel storage tank in the basement of a hospital. The tank is under 8-ft tall.

I have researched NFPA 13, 16, and NFPA 30. I used the tables for sprinkler type and criteria.

My confusion is the amount of storage and the size of the tank.

The tables in NFPA 30, starting with Chapter 16.5.2.1, have guidelines for tank sizes up to 60 gallons only. This is a much larger, metal, stationary tank (3,000 gallons).

What table or design criteria can be used?

K-factors of 8.0 or 11.2 - and 0.30 or 0.40 density?

We will be using foam for this project and I just want to be sure that I'm approaching and educating myself for the correct approach without missing or violating limitations within NFPA 30 (or the other standards). Thanks for the help!

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8 Comments

Jose Pinies

11/8/2023 08:38:15 am

I´d like to know too

Adam

11/8/2023 08:48:11 am

I am not experienced in this topic, either, but it appears that NFPA 30, Chapter 16 does not apply due to such tanks being excluded under 9.1.4 sentence (2).

See NFPA 30 16.4.1. and the associated flow charts.

Where to go next? I'll have to leave that to someone else!

Anthony

11/8/2023 09:34:30 am

What we're missing is a code path something pointing you to a particular code/standard. Generally building code will point you to NFPA 13. 13 will point you to 30 and 30 will point you to 11, 15

In this case Building code icc ch9 points toNFPA13. NFPA 13-2022 27.2 points you to NFPA 30. NFPA 30-2024 22.8.1(1) point you to NFPA 11 or 15.

I'm not an expert on 11 or 15 and will let other comment the design requirement from there.

Eric R

11/8/2023 10:44:16 am

If the jurisdiction has adopted the ICC standards then tank storage of flammable liquids actually is covered via the IFC under chapter 57.

5704.2.9.2 Fire protection.
Fire protection for above-ground tanks shall comply with Sections 5704.2.9.21 through 57042.9.2.4.

5704.2.9.2.1 Required foam fire protection systems.
Where required by the fire code official, foam fire protection shall be provided for above-ground tanks other than pressure tanks operating at or above 1 pound per square inch gauge (psig) (6.89 kPa) where such tank, or group of tanks spaced less than 50 feet (15 240 mm) apart measured shell to shell, has a liquid surface area in excess of 1 ,500 square feet (139 m2), and is in accordance with one of the following.
1. Used for the storage of Class I or II liquids.
2. Used for the storage of crude oil.
3. Used for in-process products and is located within 100 feet (30 480 mm) of a fired still, heater, related fractioning or processing apparatus or similar device at a processing plant or petroleum refinery as herein defined.
4. Considered by the fire code official as posing an unusual exposure hazard because of topographical conditions; nature of occupancy, proximity on the same or adjoining property and height and character of liquids to be stored; degree of private fire protection to be provided; and facilities of the fire department to cope with flammable liquid fires.

5704.2.9.2.2 Foam fire protection system installation.
Where foam fire protection is required, it shall be installed in accordance with NFPA 11.

NFPA 11 does have "generic" design criteria for foam systems, but also requires that other occupancy related codes take precedence if they apply. Also, since new foam systems should be SFFF type, NFPA 11 requires you to use the MFG's design densities per their listing/approval.

So for example if you went with Viking Sprinkler's USP SFFF foam for Hydrocarbons you would need a 0.22 density to meet their UL listing or a 0.30 density if you needed to use their FM approval. (Just reading off their data sheet here)

Flammable liquid storage and foam systems require a lot of time and effort to work through the code path and design process. It is generally a good idea to reach out to the manufacturer's engineering team as they really know this stuff.

11/9/2023 01:33:40 pm

Good to know! Thanks!!

Jesse

11/8/2023 10:07:37 am

I'd like to know more about the tank and the room. Regardless, 13 will push you toward NFPA 11

Michael P Venneri

11/9/2023 07:13:55 am

It is not immediately obvious but as stated above, some applications are contained in the IFC for protection of flammable liquids. These designs are acceptable to most unless the IFC is not adopted by the Jurisdiction.
One word of caution is that the new SFFF foam may have a different and increased density than what is contained in the codes referenced for AFFF. There are also specific requirements for foam systems by manufacturer depending on what the equipment is. Most manufacturers have their own listings for their own equipment. That listing will contain specifics related to sprinkler type, proportioner and other details. One day the codes will catch up but make sure whatever your design is it is run by the manufacturer. Especially of a retrofit situation.

Franck

11/11/2023 04:21:35 am

There is no detailed/precise information in NFPA 11 for the design parameters of the sprinkler/deluge system (chapter 6).
The only information is that the area of application should normally be 5000 sq ft (except of occupancy states otherwise):

6.5.2.2.2.1 Total Design Area.
(A) * The total design area shall be 5000 ft2 (465 m2).

(B) Where applicable occupancy standards specify design areas different from that specified in 6.5.2.2.2.1(A), the occupancy standards shall take precedence.

More practical information is found in NFPA 15 in chapter 7.4 Exposure Protection.

The purpose of the protection of the diesel tank is to avoid that a fire in the surrounding can make troubles to the tank (and its content) and in case of fire involving the tank that it creates unecessary exposure to the outside.

Recommended protection is then found in:

7.4.2 * Vessels.
7.4.2.1
Water spray shall be applied to vessel surfaces (including top and bottom surfaces of vertical vessels) at a net rate of not less than 0.25 gpm/ft2 [10.2 (L/min)/m2] of exposed surface.

Do not forget to provide sprinkler protection below the tanks as they may be exposed to a pool fire and water spray may be ostructed by the tank itself.

7.4.2.5
Where projections (manhole flanges, pipe flanges, support brackets, relief valves, etc.) will obstruct water spray coverage, including rundown on vertical surfaces, additional nozzles shall be installed around the projections to maintain the wetting pattern that otherwise would be seriously interrupted.

I personally generally recommend a sprinkler protection with K8.0, 286°F rated sprinklers with a minimum density of 0.3 gpm/sq ft (12.2 mm/min) over the entire room (or up to 2500 sq ft (232 m2) as it would be for an EH group 1 occupancy.
And same density in the case of deluge system.
This is also in line with recommendations from FM data sheet 7.32 (IGNITABLE LIQUID OPERATIONS).
Information is detailed in Table 2.4.3. Sprinkler Protection for Occupancies Using Ignitable Liquids

Note that there is no need to provide film forming foam in addition to the water spray protection. But this not an issue if provided anyway.

Foam Design Criteria for Diesel Storage Tank?

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