NATURAL GAS—CHEMICAL AND PHYSICAL PROPERTIES
concentration or LEL (lower explosive level) or LFL (lower flammable limit). Natural gas requires a concentration in air of 4% gas or 40,000 ppm (LEL) to a UEL (upper explosive level) of 15% or 150,000 ppm. At less than 1 ppm the odor can be detected well below the concentrations that are flammable. Odorized natural gas can be detected by the nose even before the presence of gas can be identified even by a Combustible Gas Indicator. Remember, because the odorant in natural gas can be detected as low as 1 part per million— that is an enormous safety advantage! Responders should never take the odor of gas lightly. In any leak of utility gas notifying the utility company is imperative. Responders and utility companies can also use direct reading instruments such as Combustible Gas Indicators or Flame Ionization Detectors to determine if a flammable atmosphere does exist.
NATURAL GAS — CHEMICAL AND PHYSICAL PROPERTIES
Natural gas is a very effective, clean and effi- cient fuel. It is soluble in alcohol but not soluble in water. It is used as a fuel because of its high heat of combustion. Natural gas is not an ele- ment; it is a mixture of gases such as methane, ethane, propane, and other residual chemicals like carbon dioxide and nitrogen. It is usually found in distribution as a compressed gas but can be stored and transported in the liquefied state, called LNG or liquefied natural gas which is cryogenic gas and extremely cold at a temper- ature of -259ºF (-162ºC).
Physical Properties
Physical properties can be observed or measured without changing the com- position of the material. They are used to observe and describe why some chemicals float on water like gasoline, others rise in the air like helium, and still others, like ethyl alcohol, mix well with water. In an accidental release the physical properties of a gas will dictate how a chemical moves and be- haves after it escapes. Knowledge of the physical properties of natural gas will be invaluable to the responder’s assessment of the emergency. Those physical properties that impact a natural gas emergency are:
• Vapor density • Specific gravity • Water solubility • Vapor pressure • Boiling point • Expansion ratio
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Click here for MSDS for natural gas and tertiary butyl mercaptan.
For more information click here.
http://en.wikipedia.or g/wiki/Butanethiol
FIGURE 2.5 MSDS station.
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