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66.24 Storage Tank Buildings
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This section shall also apply to installations of aboveground storage tanks storing Class II, Class IIIA, or Class IIIB liquids in storage tank buildings where the liquids are heated at or above their flash points. In such cases, the liquids shall be regulated as Class I liquids unless an engineering evaluation conducted in accordance with Section 66.6 justifies following the requirements for some other liquid class. [30:24.1.2]
This section shall not apply to the following:
- Tanks covered by Sections 66.17, 66.18, and 66.19.
- A tank that has a canopy or roof that does not limit the dissipation of heat or dispersion of flammable vapors and does not restrict fire-fighting access and control. Such tanks shall comply with the provisions of this Code.
Tanks and associated equipment within the storage tank building shall be so located that a fire in the area shall not constitute an exposure hazard to adjoining buildings or tanks for a period of time consistent with the response and suppression capabilities of the fire-fighting operations available to the location. Compliance with 188.8.131.52 through 184.108.40.206 shall be deemed as meeting the requirements of 220.127.116.11. [30:24.4.1]
The minimum distance from exposed property lines and buildings for tank installations within structures having walls with a fire resistance rating of less than 2 hours shall be in accordance with Table 18.104.22.168. [30:24.4.2]
|Largest Tank — Operating Liquid Capacity (gal)||Minimum Distance from Property Line that Is or Can Be Built Upon, Including Opposite Side of Public Way (ft)||Minimum Distance from Nearest Side of Any Public Way or from Nearest Important Building on Same Property (ft)|
|Stable Liquid Emergency Relief||Unstable Liquid Emergency Relief||Stable Liquid Emergency Relief||Unstable Liquid Emergency Relief|
|Not over 2.5 psi||Over 2.5 psi||Not over 2.5 psi||Over 2.5 psi||Not over 2.5 psi||Over 2.5 psi||Not over 2.5 psi||Over 2.5 psi|
|Up to 12,000||15||25||40||60||5||10||15||20|
|12,001 to 30,000||20||30||50||80||5||10||15||20|
|30,001 to 50,000||30||45||75||120||10||15||25||40|
|50,001 to 100,000||50||75||125||200||15||25||40||60|
For SI units, 1 gal = 3.8 L; 1 ft = 0.3 m; 1 psi = 6.9 kPa. [30:Table 24.4.2]
Where a storage tank building has an exterior wall facing an exposure, the distances in Table 22.214.171.124 shall be permitted to be modified as follows:
- Where the wall is a blank wall having a fire resistance rating of not less than 2 hours, separation distance between the storage tank building and its exposure shall not be required to be greater than 25 ft (7.6 m).
- Where a blank wall having a fire resistance rating of not less than 4 hours is provided, the distance requirements of Table 126.96.36.199 shall not apply.
- * Where Class IA liquids or unstable liquids are stored, the exposing wall shall have explosion resistance in accordance with recognized engineering standards, and deflagration venting designed in accordance with NFPA 68 shall be provided in the nonexposing walls and roof.
Other equipment associated with tanks, such as pumps, heaters, filters, and exchangers, shall not be located closer than 25 ft (7.6 m) to property lines where the adjoining property is or can be built upon or to the nearest important building on the same property that is not an integral part of the storage tank building. This spacing requirement shall not apply where exposures are protected as outlined in 188.8.131.52. [30:24.4.6]
Storage tank buildings shall be constructed so as to maintain structural integrity for 2 hours under fire exposure conditions and to provide access and egress for unobstructed movement of all personnel and fire protection equipment. Compliance with 184.108.40.206 through 220.127.116.11 shall be deemed as meeting the requirements of 18.104.22.168. [30:24.5.1]
Buildings or structures shall be of at least 2-hour fire resistance rating. [30:24.5.2]
Where Class I liquids are stored above grade within buildings with basements or other belowgrade areas into which flammable vapors can travel, such belowgrade areas shall be provided with mechanical ventilation designed to prevent the accumulation of flammable vapors. Enclosed storage tank pits shall not be considered basements. [30:24.5.3]
Storage tank buildings where Class IA liquids are stored shall be designed to direct flame, combustion gases, and pressure resulting from a deflagration away from important buildings or occupied areas through the use of damage-limiting construction. The damage-limiting construction design shall be designed in accordance with NFPA 68 and shall be acceptable to the AHJ. [30:24.5.4]
A clear space of at least 3 ft (0.9 m) shall be maintained between the top of each tank and the building structure for buildings protected in accordance with 22.214.171.124.3. For buildings without fixed fire suppression systems, sufficient clear space shall be provided to allow for the application of hose streams to the top of the tank(s) for cooling purposes. [30:24.5.7]
Where the need is indicated in accordance with 126.96.36.199, mobile foam apparatus shall be provided. [30:188.8.131.52]
Where the need is indicated by the hazards of storage or exposure as determined by 184.108.40.206, fixed protection shall be required utilizing approved foam, foam-water sprinkler systems, sprinkler systems, water spray systems, deluge systems, gaseous extinguishing systems, dry chemical extinguishing systems, fire-resistive materials, or a combination of these. [30:220.127.116.11]
If provided, fire control systems shall be designed, installed, and maintained in accordance with the following NFPA standards:
- NFPA 11, Standard for Low-, Medium-, and High-Expansion Foam
- NFPA 12, Standard on Carbon Dioxide Extinguishing Systems
- NFPA 12A, Standard on Halon 1301 Fire Extinguishing Systems
- NFPA 13, Standard for the Installation of Sprinkler Systems
- NFPA 15, Standard for Water Spray Fixed Systems for Fire Protection
- NFPA 16, Standard for the Installation of Foam-Water Sprinkler and Foam-Water Spray Systems
- NFPA 17, Standard for Dry Chemical Extinguishing Systems
- NFPA 25, Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems
Installation of electrical utilization equipment and wiring shall meet the requirements of Section 66.7. [30:24.8.1]
Section 66.7 shall be used to determine the extent of classified locations for the purpose of installation of electrical equipment. [30:24.8.2]
In establishing the extent of a classified location, it shall not extend beyond a floor, wall, roof, or other solid partition that has no openings within the classified area. [30:18.104.22.168]
Except for drains, solid floors shall be liquidtight and walls shall be liquidtight where they join the floor and for at least 4 in. (100 mm) above the floor. [30:24.9.3]
The containment shall have a capacity not less than that of the largest tank that can drain into it. [30:24.9.6]
Storage tank buildings storing Class I liquids or Class II or Class III liquids at temperatures at or above their flash points shall be ventilated at a rate sufficient to maintain the concentration of vapors within the building at or below 25 percent of the lower flammable limit. Compliance with 22.214.171.124 through 126.96.36.199 shall be deemed as meeting the requirements of 188.8.131.52. [30:24.10.1]
Ventilation shall be designed based on one of the following:
- Calculations based on the anticipated fugitive emissions (See Annex E of NFPA 30 for calculation methods.)
- Sampling of the actual vapor concentration under normal operating conditions
- Ventilation at a rate of not less than 1 cfm of exhaust air for each square foot of solid floor area (0.3 m3/min/m2)
If vapor concentrations are confirmed by sampling, the sampling shall be conducted at a distance of a 5 ft (1.5 m) radius from each potential vapor source extending to or toward the bottom and the top of the enclosed storage area. The vapor concentration used to determine the required ventilation rate shall be the highest measured concentration during the sampling procedure. [30:184.108.40.206]
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