Acetylene flammability limits

Precautions also have to be instituted to protect against the inherent properties of the cylinder contents, e.g. toxic, corrosive, flammable (refer to Table 9.1). Most gases are denser than air common exceptions include acetylene, ammonia, helium, hydrogen and methane. Even these may on escape be much cooler than ambient air and therefore slump initially. Eventually the gas will rise and accumulate at high levels unless ventilated. Hydrogen and acetylene, which both have very wide flammable limits (Table 6.1), can form explosive atmospheres in this way. 

Typical examples that present the greatest fire risk particularly in rooms or poorly ventilated spaces are hydrogen, acetylene, ethylene, carbon monoxide, ammonia and service gas. Normally gases are stored, handled and processed inside containers, vessels or pipes but when leaks occur the fuel concentration in the atmosphere can rise to the lower flammable limit. In well ventilated places the risk is less, but flammable mixtures can occur in the immediate region of the leak. 

Acetylene acts as an asphyxiant by diluting the oxygen in the air to a level that will not support life. However, prior to reaching a level where suffocation could occur, the lower flammable limit will have been reached, and this constitutes a most serious hazard. 

Flammable gases are defined by the U.S. Department of Transportation as those that when mixed with air are flammable in concentrations of 13 percent or less by volume in air or, if the gas has a flammable range wider than 12 percent in air, regardless of its lower flammable limit. Examples of flammable gases include acetylene, butadiene, carbon monoxide, ethane, ethylene, hydrogen, hydrogen sulfide, the liquefied petroleum... 

Acetylene burns in air with an intensely hot, luminous, and smoky flame. The ignition temperatures of acetylene and of acetylene-air and acetylene-oxygen mixtures vary according to composition, initial pressure, initial temperature, and water vapor content. As a typical example, an air mixture containing 30 percent acetylene by volume at atmospheric pressure can be ignited at about 581 °F (305°C). The flammable limits of acetylene-air and acetylene-oxygen mixtures similarly depend on initial pressure, temperature, and water vapor content. In air at atmospheric pressure, the upper flammable limit is about 80 percent acetylene by volume and the lower limit is 2.5 percent acetylene. Some references list the upper flammable limit as 100 percent, which is due to the de-... 

For most flammable hydrocarbons, the LFL is around 2%—5%. For simple alkanes, such as methane and ethane, the UFL is in the 10%—15% range. Some chemicals, such as hydrogen, ethylene oxide, and acetylene, have much higher values for UFL. Values for flammable limit ranges for many flammable materials are provided by NFPA 704—Standard System for the Identification of the Hazards of Materials for Emergency Response. 

Calcium carbide, CaC2, reacts with water to form calcium hydroxide and the flammable gas ethyne (acetylene). This reaction was once used for lamps on bicycles, because the reactants are easily transported, (a) Which is the limiting reactant when 1.00 X 102 g of water reacts with 1.00 X 102 g of calcium carbide (b) What mass of ethyne can he produced (c) What mass of excess reactant remains after reaction is complete Assume that the calcium carbide is pure and that all the ethyne produced is collected. The chemical equation is... 

F0-E°/T 46.96 c ° 13.31 (all in cal/deg mol) S°56.40 eu, H0, F0, c° S° are respectively standard heat of formation, stand free energy of form heat capacity std entropy. E° is heat of formation of a perfect gas. at abs zero (Ref 10) Acetylene chloride behaves very unpredictably It is spontaneously flammable in air and it explodes when heated in air or shocked. On pyrolysis it gives off the very toxic phosgene (Ref 8). An attempt at defining its explosion limits is made m Ref 2... 

Hazard Very flammable, dangerous fire risk burns with intensely hot flame explosive limits in air 2.5-80%. Forms explosive compounds with silver, mercury, and copper, which should be excluded from contact with acetylene in transmission systems. Copper alloys may be used with caution. Piping used should be electrically bonded and grounded. 

CHLOROMETHANE (74-87-3) CH3CI Highly flammable gas [explosion limits in air (vol %) 8.1 to 17.2 flashpoint <32°F/<0°C autoignition temp 1170°F/632°C Fire Rating 4]. Moisture causes decomposition. Violent reaction with strong oxidizers, acetylene, anhydrous aluminum trichloride, ammonia, amines, ethylene, fluorine, interhalogens magnesium, potassium, powdered aluminum or zinc, sodium, and... 

---