Deflagrations Subject

The deflagration flame arrester must he subjected to a series of at least 10 explosion (deflagration) tests in a rig with a pipe at least 5 feet (1.5 meters) long with various mixtures of propane in air and different test conditions to test the entire spectrum of possible deflagrations. Also, a series of 3 flashback tests, using a mixture of 4.2 volume percent of propane in air, must be conducted. 

A UL Type 1 deflagration flame arrester must undergo an endurance burn test while a UL Type 11 deflagration flame arrester must be subjected to a continuous flame test. The test conditions for the endurance burn test and the continuous flame test for a deflagration flame arrester are the same as for a detonation flame arrester. 

Continuous Flame Test A test in which a flame arrester is subjected to flame of a continnonsly burning mixture (as specified in UL 525 for deflagration or detonation flame arresters) on the outlet face of the arrester for one hour (or longer at the manufacturer s request). 

Figure 7-63A. Venting nomograph for methane. Reprinteed with permission, NFPA 68-1988, Deflagration Venting, (1988) National Fire Protection Association, Quincy, MA 02269. Note This materiai is not the complete and official position of the National Fire Protection Association on the referenced subject, which is represented only by the standard in its entirety. Note from this author this statement applies to all material referenced for use that originates with the National Fire Protection Association [27].

These substances decompose rapidly to produce large volumes of gas. They are substances not classified as deflagrating or detonating explosives but exhibit violent decomposition when subject to heat. 

When large quantities of a substance are handled, sensitivity of the material to heating under confinement may need to be considered to demonstrate the effect on the stored/handled, and probably confined, substance in the event of an external heat load. Tests such as the steel sleeve test or Koenen test [24, 137], the Dutch pressure vessel test (DPVT) [143], and the United States pressure vessel test (US-PVT) [143] may be applicable. These tests are used mostly for transportation considerations. The tests generally subject the sample substances to very high energy inputs under confined conditions, and thus are more severe than the deflagration and autoclave tests previously discussed in Section 2.3.3.2. As an example, the Koenen test, used mainly in Europe, is illustrated in Figure 2.32. 

The physicochemical properties of explosives are fundamentally equivalent to those of propellants. Explosives are also made of energetic materials such as nitropolymers and composite materials composed of crystalline particles and polymeric materials. TNT, RDX, and HMX are typical energetic crystalline materials used as explosives. Furthermore, when ammonium nitrate (AN) particles are mixed with an oil, an energetic explosive named ANFO (ammonium nitrate fuel oil) is formed. AN with water is also an explosive, named slurry explosive, used in industrial and civil engineering. A difference between the materials used as explosives and propellants is not readily evident. Propellants can be detonated when they are subjected to excess heat energy or mechanical shock. Explosives can be deflagrated steadily without a detonation wave when they are gently heated without mechanical shock. 

Burning (Combustion) and Deflagration of Gases, Vapors ond Dusts. As this subject was not discussed in previous volumes of Encycl, such as under Burning in Vol 2 of Encycl, nor under "Combustion in Vol 3, we are including it here... 

The following comments on the subject of transition from combustion or deflagration to detonation was communicated to us by Dunkle (Ref 35)i... 

Prior to reading this subject, it is advisable to see "Burning (Combustion) and Deflagration of Gases, Vapors and Dusts Detonation and Explosion of Dusts and Mists (Vapors) and Detonation (or Explosion), Development (Transition) from Burning (Combustion) or Deflagration described in this Volume... 

Deflagrations (Ref 66, pp 144-45). This subject is also described in our writeup on p D207ff... 

Sensitivity and Hazards ofLP. Some mono-proplnts and some well-mixed biproplnts exhibit detonation characteristics typical of Liquid Explosives (See Sects 4 5 of article on Liquid Explosives in this Vol). However, biproplnts usually do not sustain complete detonation, ie, a rather small portion of the biproplnt undergoes something akin to detonation and the remainder deflagrates (Ref 26). Of course even this partial detonation can be very dangerous and destructive. LP are also subject to another phenomenon which is potentially destructive (at least to the rocket), namely combustion instability (Refs 16 22)... 

There is reason to believe that the measurement of burning rate should be of interest to the chemical industry. A number of materials that are handled can deflagrate, particularly if subjected to elevated temperature and pressure certain organic material containing nitrate, nitro, peroxide, and certain other oxidizing species are examples. It is important to know what these rates are and how they depend on temperature and/or pressure in order to know whether or not they constitute an industrial hazard. 

A substance is classed as a deflagrating explosive when a small amount of it in an unconfined condition suddenly ignites when subjected to a flame, spark, shock, friction or high temperatures. Deflagrating explosives burn faster and more violently than ordinary combustible materials. They burn with a flame or sparks, or a hissing or crackling noise. 

Vanadyl Azide Trichloride. V0(N3)C13, G3N3OV mw 215.33 cryst. Sol in V oxytri-chloride. Prepn is by bubbling a mixt of chlorine azide and nitrogen thru V oxytrichloride at RT. The compd deflagrates with great vigor on being subjected to thermal shock (Ref 17)... 

Detonating Ignition. This term, which was introduced by Ramsay Weston (Ref), refers to initiation by a strong local expln instead of by a spark or flame. For example, a mixt of charcoal and saltpeter (without sulfur) is not explosive but will burn on contact with flame or spark but not on impact. If, however, a small amt of NG will be added and the mixt subjected to an impact, a powerful expln will result. This is because NG will detonate and the resulting hot flame will deflagrate the mixt of charcoal and saltpeter (See also under Detonating Explosives) Ref A.F.J. Ramsay H.C. Weston, "Manual on Explosives , Routledge, London (1916), 80... 

The sources and magnitudes of thermochemical data have been the subject of many entries in this Encycl. The use of the data presupposes a general acquantance with chemical thermodynamics (next article) and with detonation theory (Vol 4, D268-L to D298-R). The principle difference between classic thermodynamics and the thermochemistry of reactive systems is that expins and deflagrations do not represent equilibrium processes. In principle, the heat of reaction is obtained by ... 

Properties They are high explosives and are characterized by relatively great sensitivity to beat or shock. They detonate when subjected to heat or shock and are set off by the spit of a black-powder fuse, by the heat of an electrically heated wire, by percussion (firing pin), or by friction. Their detonation produces flame and shock, which are used to initiate the deflagration of powder or the detonation of high explosives. ... 

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