Hazard Fuel and electrical systems
Knowledge and understanding
|Fuel and electrical systems||
Understand all associated hazard knowledge
The hazards present at a transport incident due to live vehicle electrical systems and unmanaged fuel may be a direct result of an accident, fire or may occur during emergency service operations.
Throughout the transport networks, various vehicles and craft will feature a range of different power sources. These can include:
- Batteries: lead acid, alkaline and lithium metal batteries. See National Operational Guidance: Hazardous materials
- Engine driven generators that provide the main power
- Auxiliary power units that provide essential power
- Fixed electrical ground power is used in lieu of the auxiliary power units
See also specific Road guidance relating to alternative fuelled vehicles.
Batteries, generators, high voltage connections or pantographs may all be encountered when dealing with rail vehicles. Because of the variety of systems available, specific information gathering should take place at each incident to identify the source and nature of the electrical hazards present.
Electrical sockets are increasingly available to power customer devices, catering facilities and air conditioning units. These all require increased electrical generation, components and cabling.
Traction equipment and batteries are usually housed in the underframe area, the majority of which are encased in metal skirts. Other electrical equipment and cables may be located in a carriage roof. Creating access points into train bodywork could expose cabling that may range in voltage from 110v to 875v.
The primary function of an aircraft electrical system is to generate, regulate and distribute electrical power throughout the aircraft. The aircraft electrical power system is used to operate:
- Aircraft flight instruments
- Essential systems such as anti-icing (The power that the aircraft needs to be able to continue safe operation)
- Passenger services (The power used for cabin lighting, entertainment systems and food preparation)
- Ignition systems in light aircraft
Aircraft electrical components operate on many different voltages, both alternating current (AC) and direct current (DC). However, most of the aircraft systems use 115 volts (v) AC at 400 hertz (Hz) or 28 volts DC. In some aircraft, 26 volts AC is also used for lighting.
Electrical systems are used throughout the aviation industry on larger commercial and military aircraft. It is reasonable to assume they will be present at all aviation incidents involving commercial and military aircraft.
Aircraft fuels fall broadly into two types: gasoline or AVGAS (petrol), and kerosene or AVTUR (jet fuel).
Principal hazards from fuels are that they can be:
- Highly flammable
- Transported in large volumes
Post accident fire and rescue service operations can pose a significant hazard in relation to fuel spillages on or around the crash site.
When the vapour given off from aviation fuels is mixed with air and then ignited, a flame zone develops above the surface of the fuel. As the temperature rises the rate of vaporisation increases. The development of a flame zone and the rate of vaporisation accelerate each other. Aviation fuel fires therefore reach peak intensity very rapidly as the fuel develops intense heat when burning.
As a result of its high vapour pressure and low flash point, AVGAS vapour can be readily ignited with a spark or flame at ambient temperatures. However, liquid AVGAS must reach a moderately high temperature before it can auto ignite (450ºC).
Liquid AVTUR will not ignite under normal temperature. As a result of its low vapour pressure and moderate flash point, AVTUR vapour cannot be readily ignited by spark or flame at ambient temperature. It will auto ignite at a fairly high temperature (245ºC).