Types of Flame Arresters

This section describes varions types of flame arresting elements (matrixes) that are nsed in fixed element (stadc) dry type flame arresters, as well as a nnmber of other types. Some of these arresting elements are often nsed in bodi deflagradon and detonadon flame arresters. 

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One of the major reasons that this book was written is that nonspecialist chemical engineers know little abont DBAs. Althongh DBAs have been specified and installed for many years, qnite often they have failed becanse the wrong type of flame arrester was specified, or it was improperly installed, or inadeqnate inspection and maintenance were provided. 

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-... 

The flame propagation direction affects the type of flame arrester selected. An end-of-line or in-line deflagration flame arrester used for the protection of an individual tank may be of a unidirectional design because the flame will only propagate from the atmosphere towards the tank interior. A bidirectional flame arrester design, however, is needed for an in-line application in a vapor recovery (vent manifold) system because the vapors must be able to flow from the tank interior into the manifold, or from the manifold into the tank interior. Consequently, flame may propagate in either direction. 

In many sitnations several types of flame arresters are snitahle for the application. Often pressure drop dnring normal operation and its possible increase over the flame arrester s service life may he the primary determinant in selection of a snitahle nnit. 

Deflagration and detonation flame arresters should be inspected annually until operating experience indicates otherwise. Also, the need for frequent inspection and maintenance may affect the selection of one type of flame arrester over another type for a specific application. For example, a hydraulic (liquid seal) flame arrester may be more suitable than a dry, fixed-element, flame arrester if the latter requires frequent inspecdon and maintenance because of persistent plugging problems. 

Several types of flame arresters have been tested for hydrogen service and fonnd acceptable for qnenching of hydrogen-air and hydrogen-methane-air mixtnres. 

Acetylene may propagate decomposition flames in the absence of any oxidant above certain minimum conditions of pressure, temperature, and pipe diameter. Acetylene, unlike most other gases, can decompose in a detonative manner. Among the different types of flame arresters that have proven successful in stopping acetylene decomposition flames are hydraulic (liquid seal) flame arresters, packed beds, sintered metal, and metallic balls (metal shot). 

Proper training on the operation and maintenance of flame arresters shonld be given to the appropriate personnel so that they will become competent with respect to the operating characteristics of the varions types of flame arresters nsed in a plant, as well as their specific inspection and maintenance reqnirements. 

Appendix B to Part 154 is a standard specification for tank vent (end-of-line) deflagration flame arresters. It does contain test procedures for these types of flame arresters. An end-of-line flame arrester mnst be able to arrest three atmospheric deflagrations as well as to withstand two honrs of continnons bnrning withont flashback. 

A new CEN European standard, EN 12874, was issued in 2001. It will be used by all European nations that belong to the European Union (EU) that are members of the Comite Enropeean de Normalisation (CEN), as well as other non-EU nations that are members of the CEN. It will supersede BS 7224 in England, FEB and BAM in Germany, and standards in use in other European countries. This is a very comprehensive standard covering types of flame arresters not covered in US, Canadian, and other standards. It contains test procedures for the following types of flame arresters ... 

It allows more flexibility to engineers with regard to the type of flame arrester nsed and its approval, dins helping to possibly minimize problems such as maintenance, plngging, and pressure drop. 

These questions have to be clarified in order to determine the place and type of installation as well as the type of flame arrester. 

In the next step the type of flame arrester is determined. In doing this a number of boundary conditions have to be considered. Among them figure, for example, contamination with sohds, solidification temperature and condensation or... 

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