Ignition sources electrical equipment

Correct selection of heating equipment and zoning of electrical equipment to reduce the chance of an ignition source arising. 

Equipment Failures Safety system Ignition Sources Furnaces, Flares, Incinerators, Vehicles, Electrical switches. Static electricity, Hot surfaces. Cigarettes Human Failures Omission, Commission, Fault diagnosis. Decisions Domino Effects Other containment failures. Other material release External Conditions Meteorology, Visibility... 

The source of ignition may have been a box containing electrical equipment. It had a badly fitted or incorrect type of plug, which could have allowed water to enter and to cause arcing. 

Ignition in 23% of the cases where this occurred, the source was unknown in about a third of the incidents in which the source was known, it was auto-ignition. Other common sources were flames, hot surfaces, sparks, lighming, static electricity and electrical equipment. In many cases conditions changed after a permit-to-work had been issued (see Section 1.3.2). 

The sparking of electrical equipment, such as motors, is a major potential source of ignition, and flame proof equipment is normally specified. Electrically operated instruments, controllers and computer systems are also potential sources of ignition of flammable mixtures. 

The fire temperature for various materials, such as wood, plastic, and solvents, is approximately 1000°C. Because pure copper melts at 1080°C, copper wire usually survives fires. If copper beads are found around electrical equipment, it may indicate that electrical arcs created temperatures greater than those observed in fires. Sometimes pits at the ends of conductors indicate high temperatures and vaporization of copper while arcing. Although this type of evidence indicates a source of ignition, it may not be the primary source of the fire. 

Autoignition temperatures are vitally important for process designs as it is the temperature at which to prevent or eliminate readily available ignition sources, (e.g., operating temperatures of electrical equipment, light fixtures, etc.). 

The overall intent of electrical area classification is to provide for safety of personnel and equipment. This is achieved by the elimination of electrical ignition sources near combustible gases or vapors that could explode or bum. The specific reasons for classifying facilities into electrical hazardous areas typically are ... 

Dry chemical agents currently used are a mixture of powders, primarily sodium bicarbonate (ordinary), potassium bicarbonate (Purple K), monoammmonium phosphate (multipurpose). When applied to a fire they cause extinguishment by smothering the fire process. They will not provide securement of a flammable liquid spill or pool fire and it can re-flash after it is initially suppressed if an ignition source is present (i.e., a hot surface). Dry chemical is still very effective for extinguishment of three dimensional flammable liquid or gas fires. It is nonconductive and therefore can be used on live electrical equipment. 

Flammable These compounds have a low flash point, and those which react with water or damp air to give rise to flammable gases (e.g. hydrogen) from metal hydrides. Ignition sources include Bunsen burners, hot metal surfaces, electric sparks, etc. Fire fighting equipment should be readily available and frequently checked. 

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