Acetylene Gas- its Characteristics and Safety Requirements...

Acetylene Gas- its Characteristics and Safety Requirements Acetylene is  a gas used in steel plants for oxy-acetylene gas cutting and welding and also in flame cutting machines of continuous casting machines. It is sometimes used for carburization of steel, flame heating, flame gouging, flame hardening, flame cleaning, flame straightening, thermal spraying, spot-heating, brazing, texturing and profile-cutting, and carbon coating. Acetylene is the chemical compound with the formula C2H2. It is an unsaturated hydrocarbon and the simplest alkyne. An acetylene molecule is composed of two carbon atoms and two hydrogen atoms. The two carbon atoms are held together by what is known as a triple carbon bond having CH bond angle of 180 deg. This bond is useful in that it stores substantial energy that can be released as heat during combustion. However, the triple carbon bond is unstable, making acetylene gas very sensitive to conditions such as excess pressure, excess temperature, static electricity, or mechanical shock. Acetylene is a flammable and colourless gas. Its molar mass is 26.04 g/mol. It is unstable in pure form and thus is usually handled as a solution. Pure acetylene is odourless, but commercial grades usually have a marked garlic like odour due to impurities. It has a density of 1.11 kg/cum at 1 atmosphere pressure and 15 deg C. The specific gravity is 0.91 (air=1).  It is lighter than air so does not accumulate at low levels, where it could cause a potential hazard. The boiling point of gas is – 84.7 deg C and melting point is -80.75 deg C. The adiabatic flame temperature (AFT) in air at atmospheric pressure is 2534 deg C. The auto ignition temperature of acetylene gas is 305 deg C.  Its lower and upper explosive limits in air under STP conditions (0 deg C and 1.02 kg/sq cm) are 2.4 volume...