Oxidation, arrested

Detonation arresters are typically used in conjunction with other measures to decrease the risk of flame propagation. For example, in vapor control systems, the vapor is often enriched, diluted, or inerted, with appropriate instrumentation and control (see Effluent Disposal Systems, 1993). In cases where ignition sources are present or pre-dic table (such as most vapor destruct systems), the detonation arrester is used as a last-resort method anticipating possible failure of vapor composition control. Where vent collec tion systems have several vapor/oxidant sources, stream compositions can be highly variable and... 

Decomposition Flame Arresters Above certain minimum pipe diameters, temperatures, and pressures, some gases may propagate decomposition flames in the absence of oxidant. Special in-line arresters have been developed (Fig. 26-27). Both deflagration and detonation flames of acetylene have been arrested by hydrauhc valve arresters, packed beds (which can be additionally water-wetted), and arrays of parallel sintered metal elements. Information on hydraulic and packed-bed arresters can be found in the Compressed Gas Association Pamphlet G1.3, Acetylene Transmission for Chemical Synthesis. Special arresters have also been used for ethylene in 1000- to 1500-psi transmission lines and for ethylene oxide in process units. Since ethylene is not known to detonate in the absence of oxidant, these arresters were designed for in-line deflagration application. 

Figure 18.3(a) Sectional view of a metal oxide surge arrester (Courtesy W.S. Industries)... 

Figure 18.3(c) 12-550 kV zinc oxide surge arresters (Courtesy Crompton)... 

A diagnostic Indicator of metal oxide surge arresters in service). 

Surge arresters - Metal oxide without gaps for a.c. 3070-3/1993 BS EN 60099-... 

ANSI/IEEE- Metal oxide surge arresters for a.c. power circuits ... 

Brown. P.B. and Miske. S.A., Jr, Applicaiion of zinc oxide slaiion class arresters. Missouri Valley Electric Association Engineering Conl erence. Kansas City. Missouri. 13 April 1978. 

S Lundquisl. J.. Sleiisirom. L.. Sehei. A. and Hansen. B.. New method for nieasuremenl of the resistive leakage currents of inelal oxide surge arresters in service. 89 SM 817 8 PWRD. IEEE (1989). 

Ozawa.. 1.. Mizukoshi. A.. Maruyama. S.. Nakano. K.. Saiio K.. Si Jetin. G.. Laioiir, Y., and Petit. A.. Pressure reliet design and performance of metal oxide surge arresters, IEEE-198.3. 

This book covers many aspects of DBA design, selection, specification, installadon, and maintenance. It explains how varions types of flame arresters differ, how they are constrncted, and how they work, ft also describes when a flame arrester is an effective solntion for mitigation of deflagrations and detonations, and other means of protection (e.g., oxidant concentration rednction) that may be nsed. It also briefly covers some aspects of dnst deflagration protection. 

Kirby (1999) reports two snccessful applications of deflagration flame arresters. In one incident, a deflagration flame arrester was installed near the junction of a collection header from an ethylene oxide process nnit with a flare stack. Although this type of flame arrester was really inappro-... 

A number of gases may decompose (self-react) and propagate flames in the absence of any oxidant provided that they are above minimum conditions of pressure, temperature, and pipe diameter. Common examples are acetylene, ethylene oxide, and ethylene. Some, like acetylene, can decompose in a detonative manner, while ethylene cannot detonate in the absence of an oxidant, whatever the run-up length (CCPS 1993). Thus, detonation arresters must be used for acetylene, but deflagration arresters may be used for ethylene, even for in-line applications. 

---