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Subchapter 7. General Industry Safety Orders
Group 20. Flammable Liquids, Gases and Vapors
Article 143. Processing Plants

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§5557. Storage.

(a) The storage of flammable or combustible liquids in tanks shall be in accordance with the applicable provisions of Article 145, Tank Storage.

(b) Storage tanks inside of buildings shall be permitted only in areas at or above grade which have adequate drainage and are separated from the processing area by construction having a fire resistance rating of at least two hours. Day tanks, running tanks and surge tanks are permitted in process areas. Openings to other rooms or buildings shall be provided with noncombustible liquid-tight raised sills or ramps at least 4 inches in height, or the floor in the storage area shall be at least 4 inches below the surrounding floor. Openings shall be provided with approved self-closing fire doors. The room shall be liquid-tight where the walls join the floor. (See Article 2 for exit requirements).

(c) The storage of flammable or combustible liquids in containers shall be in accordance with the applicable provisions of Article 141, Container and Portable Tank Storage.

(d) Piping, valves and fittings shall be in accordance with Article 146, Piping, Valves and Fittings.

(e) Piping containing flammable or combustible liquids shall be identified. See Section 3321.

(f) The transfer of large quantities of flammable or combustible liquids shall be through piping by means of pumps or water displacement. Except as required in process equipment, gravity flow shall not be used. The use of compressed air as a transferring medium shall be prohibited.

(g) Positive displacement pumps shall be provided with pressure relief discharging back to the tank or to pump suction.

(h) Equipment shall be designed and arranged to prevent the unintentional escape of liquids and vapors and to minimize the quantity escaping in the event of accidental release.

Note: Where the vapor space of equipment is usually within the flammable range, the probability of explosion damage to the equipment can be limited by inerting, by providing an explosion suppression system, or by designing the equipment to contain the peak explosion pressure which may be modified by explosion relief. Where the special hazards of operation, sources of ignition, or exposures indicate a need, consideration shall be given to providing protection by one or more of the above means. NFPA 69-2002, Standard on Explosion Prevention Systems, provides information on inerting.


Authority cited: Section 142.3, Labor Code. Reference: Section 142.3, Labor Code.


1. Amendment filed 7-16-76; effective thirtieth day thereafter (Register 76, No. 29).

2. Editorial correction of subsection (h) (Register 2003, No. 30).

3. Change without regulatory effect amending sesubsection (h) and adding Note filed 7-21-2003 pursuant to section 100, title 1, California Code of Regulations (Register 2003, No. 30).

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