NFPA 326 -1999 Standard for the Safeguarding of Tanks and Containers for Entry, Cleaning, or Repair.
Flammable Vapor. Any substance that exists in the gaseous state at normal atmospheric temperature and pressure and that is capable of being ignited and burned when mixed with the proper proportions of air, oxygen, or other oxidizer. Hazardous Substance. A substance, including combustible and flammable liquids and flammable gases, that is capable of creating harm to people, the environment, or property due to the dangers that can arise from but are not limited to toxicity, reactivity, ignitibility, or corrosivity. Hot Tapping. The technique of welding and drilling on in- service tanks or containers that contain flammable, combusti- ble, or other hazardous substances. Hot Work. Any work that is a source of ignition, including open flames, cutting and welding, sparking of electrical equip- ment, grinding, buffing, drilling, chipping, sawing, or other similar operations that create hot metal sparks or surfaces from friction or impact. Inert Gas. Any gas that is nonflammable, nonreactive, and noncontaminating. Inerting. A technique by which the atmosphere in a tank or container is rendered nonignitible or nonreactive by the addi- tion of an inert gas. Liquid. Any material that has a fluidity greater than that of 300 penetration asphalt when tested in accordance with ASTM D 5, Standard Test Method for Penetration of Bituminous Materials. Unless otherwise specified, the term liquid includes both flam- mable and combustible liquids.
3-2 Removal of Flammable, Combustible, or Other Hazardous Substances, Liquids, or Gases. 3-2.1 Prior to opening the tank or container, as much hazard- ous substance, water, and sediment as practical shall be removed from the tank or container using fixed piping and connections. This process shall include the removal of liquids or gases from any internal piping, traps, and standpipes that can be drained or pumped without opening the tank or con- tainer. All piping or similar conveyances for flammable, com- bustible, or other hazardous substances connected to the tank or container shall be drained, flushed, or isolated. Where reactivity and solubility are not a concern, water shall be per- mitted to be pumped into the tank or container through fixed piping or connections to float any remaining liquid from a low spot so that it can be drained or pumped from the tank or con- tainer. 3-2.2* Where flammable or combustible liquids or vapors are contained or have been contained in a tank or container, explosionproof, steam-driven or air-driven pumps shall be used. Pump motors and suction hoses shall be bonded to the tank or container to prevent static electricity ignition hazards. 3-2.3 All liquids, rinseates, solid residues, and vapors that are generated as a result of these cleaning and safeguarding pro- cedures shall be disposed of properly in accordance with the appropriate regulatory requirements. 3-2.4 Any remaining product in the tank that is incapable of being removed as described in 3-2.1 through 3-2.3 shall remain in the tank until the tank is safeguarded and properly opened for product removal. (See Chapter 7 for tank entry requirements.)
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