Duration of burn

Duration of burning The incendiary materials must not only impart high temperatures but also maintain heat generation without replenishment of fuel. The heat must continue to radiate for an appreciable time and when the heated object is ready to bum, the fire must be present to ignite it. In fact two factors viz. intensity of heat and duration of burning are complementary to each other and must satisfy the purpose of incendiary materials. 

In fireworks, the maintenance of a definite duration of burning is especially necessary where set pieces are used, or where rotations are required and the like. It is less necessary in the case of rockets, when they are to be let off together in the form of a fan, etc., or in a quantity of squibs, because the composition and compression of the... 

The duration of burning is determined with a stop-watch, and is of importance in the case of set pieces, in which several kinds of mixtures are present. The time can then be regulated by altering the depth of the mixture in the cases shorter cases for slower mixtures, and longer cases for quicker mixtures, can be used. 

ASTM D 470-81 uses the same test chamber with a 254 mm long piece of wire mounted horizontally between two clamps at 203 mm from one another. The wire is ignited by a 102 to 127 mm long flame for 30 s. Cotton wool is placed 240 mm below the ignition point. The length and duration of burning is observed and it is recorded whether the cotton has flared up. 

The duration of the fire test for air accident qualification was set at 60 min. Statistical data on fires resulting from air accidents support the conclusion that the 60 min thermal test exceeds most severe fire environments that a package would be likely to encounter in an aircraft accident. Fire duration statistics are frequently biased by the duration of burning of ground structures and other features not related to the aircraft wreckage, as well as by the location of consignments involved in the accident. To account for this effect, information on fire duration was evaluated carefully to avoid bias by accounts of fires that did not involve the aircraft. The fire test has the same characteristics as those specified in para. 728. 

The scope of this test is to determine the ability of materials to self-extinguish (i.e., upon removal of an ignition source, the material ceases to burn.) The flame is applied to the sample twice for 10 sec. There are three possible ratings for this test based on the duration of burning after the ignition source has been removed and the dripping behavior of the material. The criteria for each rating are shown below ... 

In organic chemistry reaction, the catalyst is often inactive due to carbon deposition on its surface. The regeneration of the catalysts often adopts the method of burning carbon. At this time, the choice of the temperature and duration of burning carbon is very important. It is not difficult to determine the appropriate conditions for burning carbon according to the exothermic peak of DTA curve. 

---