Electrical hazards Flashcards
The majority of fires of electrical origin occur due to poor installation, poor or lack of maintenance or the mis-use of electrical systems and apparatus. Electricity is capable of igniting insulation or other combustible material if the power is misused, equipment or cables are overloaded or are not properly insulated and maintained. The most common electrical causes of fires are:
(i) short circuits caused by insulation failure or during work on an installation; (ii) overheating of cables and equipment due to overloading, lack of adequate ventilation or high resistance joints; (iii) the ignition of flammable gases, vapours or dusts by sparks or heat generated by electrical equipment; (iv) the ignition of combustible substances by electro-static discharges.
Where flammable gases or vapours may be present particular care is necessary in the selection, installation and maintenance of electrical equipment. A number of types of protection have been developed both for electrical equipment and tools used in areas where flammable gases and vapours may be present. These are:
(i) Intrinsically safe equipment; (ii) Flameproof equipment; (iii) Increased safety equipment; (iv) Pressurised equipment; (v) Non-sparking equipment; (vi) Oil or sand filled equipment; (vii) Specially protected equipment.
Low voltage lines can be identified as:
(i) lines going into domestic premises. (ii) generally, low voltage lines are on wooden poles and uninsulated. However, it MUST be remembered that many wooden poles carry High Voltage lines. All poles carrying High Voltage lines SHOULD carry an appropriate warning sign (see Figure 4.6). DO NOT take the lack of a warning sign on a single pole as sufficient evidence that it is a low voltage line. Other nearby wooden poles should also be checked for warning signs. (iii) conductors are in vertical formation, (usually between 2-6 conductors). If the overhead line has been identified as low voltage, rescue of a person who it is reasonably thought to be alive can be undertaken provided that the procedures set out in 4.5(a)
Minimum Safe Approach Distances
Person 10m with fire and smoke Person with jet 20m Ariel 10m or 20m training Monitor 30m
