Fuel dispensing equipment dispenses and monitors liquid or gaseous fuel. Fuel dispensers are used to pump liquid fuels such as gasoline, diesel fuel, oil, or kerosene into a vehicle, aircraft, storage tank, or portable container. Gaseous fuel dispensers may refuel hydrogen- or syngas-powered vehicles or machinery, or simply be used to move gases from one location to another.
Liquid fuel dispensing equipment is widely distributed in developed countries in the form of automotive gas pumps (petrol pumps in Commonwealth areas).
Fuel dispenser design depends on the intended fuel type. A fuel type's volatility, flammability, boiling point, and other characteristics factor into a dispenser's design and construction.
Common liquid fuel groups include:
- Petroleum fuels include gasoline (petrol), diesel, and kerosene. Liquid petroleum fuels do not directly ignite. Instead, fumes from the fuel ignite when exposed to an ignition source and vaporize the remaining liquid, causing the liquid to burn as fumes itself. Gasoline and diesel are common automotive fuels, while kerosene is common as fuel for heaters, a component of many jet and rocket fuels, and an additive to diesel to prevent cold-temperature effects.
- Compressed natural gas (CNG) and liquefied petroleum gas (LPG) are related compressible fuel types. CNG is primarily comprised of methane, while LPG is a mixture of propane and butane. Both are relatively clean-burning but must be stored under pressure due to their low boiling points. CNG and LPG are used for cooking, heating, and increasingly as motorized vehicle fuel.
- Alcohols include ethanol, butanol, and methanol. They are employed as vehicle fuels or fuel additives in combination with gasoline.
- Specialized or uncommon liquid fuels include liquid hydrogen, ammonia, synthetic fuels, and biodiesel.
Some fuels, commonly termed fuel gases, are ordinarily gaseous. Fuel gases are used in gas burners, heaters, stoves, and occasionally to power vehicles. Before the widespread use of electric street lighting, gas-lit streetlamps burned fuel gas.
Fuel gas can be broken into two groups:
- Natural fuel gas is produced during the petroleum refining process and includes propane, butane, and regasified LPG. Natural gas, the uncompressed version of CNG, is naturally occurring in gas field deposits.
- Manufactured fuel gas is produced through artificial processes, most commonly by gasification. Manufactured gases include coal gas, water gas, syngas, wood gas, and biogas. Manufactured gas was used for lighting and cooking until the mid-20th century and is now found as gas turbine or combustion engine fuels.
Design and Operation
Typical fuel dispensers include several sections, such as hydraulic, metering, and hose/nozzle portions. The hydraulic section contains a rotary pump for drawing fuel from the storage tank and a solenoid/pilot valve to ensure that fuel flows only toward the dispenser and not back into the pump. Commercial dispensers such as those found at gas/petrol stations may house multiple units connected to different storage tanks for the purpose of supplying multiple fuels with different compositions or octane ratings.
An operational fuel dispenser contains a continuously running electric motor between the storage tank and the hydraulics portion of the unit for the purpose of maintaining a partial vacuum at the rotary pump inlet. When the nozzle opens, the storage tank draws suction pressure from the inlet, causing fuel to flow toward the pumping unit. An intermediary filter removes air bubbles or suspended solids from the fuel.
Fuel then flows through the pump and valve and into the metering unit. This portion includes mechanical gearboxes, as in older pumps, or piston meters and encoders to measure and distribute a specified amount of fuel or track fuel output. After the metering section, the fuel progresses through a flexible hose and into a nozzle that dispenses it into a vehicle or storage tank.
Fuel dispensers range from large commercial gas pumps to simple dispenser pumps for use with portable storage tanks.
- Nozzle size: Diesel dispensers use larger nozzles that are incompatible with standard vehicle fillpipes to avoid misfueling. However, this sizing is not a mandated requirement, and most diesel nozzles are color-coded.
- Pressure-sensitive nozzles restrict flow until the fuel dispensing system is pressurized.
- Breakaway valves allow the nozzle to break away from the hose and stop fuel flow if a vehicle begins moving with the nozzle still in the fillpipe.
- Dual-plane nozzles include a swivel joint to allow fueling from many different angles.
- Quick-release nozzles have a single, coaxial coupling that eliminates the need for separate filling and venting points
Products and Equipment
Manufacturers may supply complete dispensing systems or the discrete components that comprise a system. These products include fuel meters, nozzles, hydraulics systems, and individual valves or pumps.
Fuels and fuel gases are flammable, and dispensing them improperly or with faulty equipment can lead to fire or explosions. For this reason fuel dispensing equipment often conforms to specifications and recommendations contained in published standards like those listed below.
- NFPA 30A—Code for motor fuel dispensing facilities and repair garages
- UL 87A—Investigation of power-operated gasoline and ethanol dispensers
- FAA AC 150/5230-4—Aircraft fuel storage, handling, and dispensing at airports