API RP 2003:1998 pdf download.Protection Against Ignitions Arising Out of Static, Lightning, and Stray Currents
1 Scope
This recommended practice presents the current state of knowledge and technology in the Þelds of static electricity, lightning, and stray currents applicable to the prevention of hydrocarbon ignition in the petroleum industry and is based on both scientiÞc research and practical experience. Further- more, the principles discussed in this recommended practice are applicable to other operations where ignitable liquids and gases are handled. Their use should lead to improved safety practices and evaluations of existing installations and proce- dures. When the narrow limits of static electricity ignition are properly understood, Þre investigators should be encouraged to search more diligently for the true ignition sources in instances where static ignition is unlikely or impossible. This recommended practice is not required under the fol- lowing conditions: a. Static discharges may occur, but ßammable vapors are always excluded by gas freeing or inerting the atmosphere in the area of discharge. b. Product handling occurs in a closed system, and oxygen in that system is always below the minimum concentration required to support combustion, such as in the handling of liqueÞed petroleum gas (LPG). c. The ßammable concentration is always above the upper ßammable limit (UFL). This document does not address electrostatic hazards relat- ing to solids handling. (See [12] and [13] in the bibliography.)
Static electricity is generated by the movement of materi- als. It involves the separation or pulling apart of surfaces that are in intimate contact with each other. This is also referred to as frictional charging. When two bodies of dissimilar materials are in close physical contact with one another there is often a transfer of free electrons. If one or both of the materials are poor conductors, uneven charges can not quickly recombine. A sudden separation will leave the excess electrons on one of the bodies and a deÞciency of electrons on the other. If the two bodies are then insulated from their surroundings, they will tend to accumulate equal and opposite charges. The body hav- ing the excess electrons will be negatively charged and the one with an electron deÞciency will be positively charged. The electrical potential difference between the charged bodies can easily reach several thousand volts. Some common examples of separation or frictional gener- ation of static electricity are: a. Separation of liquid or gas from a hose, nozzle, faucet, or pouring spout. b. The movement of liquids, gases or solid particles relative to other materials, such as occurs commonly in operations involving ßow through pipes, mixing, pouring, pumping, Þl- tering, agitating, or other types of ßuids handling.
API RP 2003:1998 pdf download
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