Today's Fuel

Natural gas has many attributes that make it superior to gasoline, diesel and other alternative fuels.

Among the attributes are 1. cleaner emissions 2. lower fuel price 3. abundant domestic supplies 4. reduced engine maintenance costs and 5. safer characteristics.

As a vehicular fuel, natural gas is most often compressed to a pressure of 3,600 psi and dispensed to vehicles at a pressure of 3,000 psi. By concentrating natural gas for use at 3,000 psi, vehicles can achieve driving ranges that are similar to those gasoline fueled vehicles.

When dispensed to a vehicle, compressed natural gas (CNG) is stored in cylinders made of steel, aluminum or a fiberglass composite. The cylinder feeds natural gas to the engine when the ignition s turned on. However, before entering the engine, the CNG pressure undergoes several stages of regulation to bring the pressure to standard atmospheric conditions. After undergoing pressure regulation, CNG enters a mixer where it is mixed with air before proceeding into the combustion chamber.

Physical properties of Natural Gas

Chemical Composition: Natural gas is comprised of four major components, their approximate proportions are typically: methane (89%); ethane (5%); butane (5%) and propane (1%). All are consumed in the vehicle's combustion process.

Appearance: Natural Gas is colorless. Generally, leaks cannot be seen, but if strong enough can be felt or heard, and always smelled.

Odor: Natural gas is odorless prior to the addition of odorants. Ethyl and methyl mercaptans are added by the manufacturers and terrahydrothiophene may be added by gas utilities. These odorants produce the characteristic odor of natural gas. This odor is a safety factor added to the gas to allow for the detection of gas leaks just as they occur. Small amounts of the odor may be present around the NGV fueling equipment but they are not cause for alarm. None of the constituents of the odorant is going to cause any health problems to employees at the site.

Physical state

Vapor Density: Being buoyant in air, natural gas released from confinement expands rapidly and would normally quickly dissipate upwards unless it became trapped. An ultra-light balloon filled with natural gas at the minimum pressure to expand the balloon could actually float away.

Compressed Natural Gas: In the CNG fueling facilities, natural gas is compressed to approximately 3,000 pounds per square inch (psi) or higher in the site equipment. A cubic foot of natural gas at 3,000 psi would be compressed down to approximately 7 cubic inches. In this state, a cubic foot of natural gas contains 245 times as much material as a cubic foot of natural gas at normal atmospheric pressure. A cube one foot on a side would be compressed into cube roughly 2 inches on a side and a cubic foot of CNG would weigh close to 13 pounds.

Natural gas compressed to this state does not liquefy; it remains a very close dense gas.

Flammability Properties of Natural Gas

Flame Visibility: Natural gas burns with a pale, faintly luminous blue flame at a temperature of about 1100 degrees Fahrenheit. Impurities in the gas or on components in the flame envelope can cause a yellow stream to appear in the combustion flame.

Flammability: Flammability is the ability of a fuel (natural gas) to burn. However before a fuel will burn two conditions must be present. The fuel must be mixed with air or oxygen in the proper portion. The points at which a mixture is too lean or too rich to burn are called the lower explosion limit (LEL) and Upper explosion limit (UEL)

Ignition sources: For a fire to take place, along with a combustible mixture, there must be an ignition source. Flames, sparks (which can occur from a variety of sources) or even extremely hot surfaces (above 900 degree Fahrenheit) can ignite natural gas. Ignition of natural gas could result from contact with welding or grinding sparks, open flames from cigarettes, lighters, flares, etc

Auto ignition: Auto ignition means that if the temperature of the fuel/air mixture is high enough, it will ignite itself. Natural gas mat automatically ignite at temperatures exceeding 900 degree Fahrenheit.

Fir Extinguishing Media: According to the National Fire Protection Association (NFPA) Guide, nature gas fires shall be extinguished using CO2, dry chemical or halocarbon gas extinguisher.

Health Hazards of Natural Gas

Toxicity: Natural gas is practically inert, below the flammability limits and has no known acute or chronic physiological effects. In concentrations exceeding 7 percent fuel/air mixtures, it will displace oxygen necessary to sustain life and asphyxiation may occur. Therefore regulatory agencies have classified natural gas as a simple asphyxiant. The exposure guideline commonly referred to for simple asphyxiants is 1000 parts per million.

Route of Exposure: The primary route of exposure to natural gas is through inhalation. Natural gas may be present during fueling and /or repair work. Natural gas is widely used in residences and industry and the potential for serious inhalation problems is low.