This testing determines the upper and lower flammability limits of gaseous chemicals or fuels with oxidants at elevated temperature and pressure. These limits are a measure of the fire and explosion hazard associated with the gases and may be used to prevent and mitigate explosions through gas composition control and equipment design. The flammability of gaseous and liquid chemicals are measured at initial pressures from sub-atmospheric to several atmospheres. The initial test temperatures can range from ambient to over 575 °F.
MCLinc has, for example, tested ClF3 and F2 flammability with fluorocarbons, and tested flammability of propane with air. An example of explosion limit testing in a mixture of fluorine gas, fluorocarbon and nitrogen is given below. The fluorine and fluorocarbon composition is plotted as a two-parameter plot. The boundary between flammable mixtures (in the middle of the plot) and non-flammable mixtures (around the outer edges) is clearly defined.
- Apparatus MCLinc’s flammability apparatus is a metal vessel shaped like a right cylinder. It is designed and fabricated to meet guidelines of ASTM E 918-83. Maximum working pressure of the vessel is 1000 psi and it was hydrostatically tested to 1500 psi. A probe reaches to the center of the pressure vessel. An exploding fuse wire at its tip initiates each test. The fuse wire explodes with a brilliant white flash like a photographic flashbulb. Multiple component mixtures can be tested.
All components which have contact with the subject gases are constructed of inert materials that will withstand explosions like nickel, 316 stainless steel, Inconel, alumina ceramic, Teflon, Kel-F, or Viton. The vessel is insulated with firebrick and low-density silica board and mounted in a metal cabinet. A heater is used to adjust the vessel’s initial temperature over the range from ambient to greater than 575°F. Gas mixtures are made with an accuracy of better than 0.1%. with pressure measurements traceable to the National Institute of Standards and Testing (NIST). The data acquisition and firing sequence is controlled by computer.