Dry type 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. 

The concepts of the National Electrical Code (NEC) gronps and the Maxi-mnm Experimental Safe Gap (MESG) are important criteria in the selection and specification of dry type flame arresters. These are explained below. 

Dry type flame arresters with small apertures, especially detonation arresters, should not be used in services where dust is present as the arresters will probably plug. 

Monitoring the pressure drop of a dry type flame arrester is advisable to determine if the arrester is plugging. 

To ensnre reliahility, dry-type flame arresters shonld he inspected on a regular basis, as mentioned previously. Also, as discussed in Section 5.3.18, it is often the pracdce to provide pressure drop and temperatnre instm-mentadon to monitor the flame arrester condidon in service. This will provide indicadon of impending problems dial can affect the performance of the flame arrester. 

Elydranlic (liquid seal) flame arresters require attention on a regular basis similar to that for dry-type flame arresters. It is critical to ensnre that the liquid level is at the required height, and level instmmentation with alarms is recommended. Automatic addition of makeup liquid (to replace evaporation and entrainment losses) is desirable. Temperatnre instrumentation is also recommended to monitor the occurrence of sustained burning (a stabilized flame). See Section 5.3.18 for more details. 

Test procedures for liquid product detonadon arresters, hydranlic flame arresters, high velocity vent valves, and flow controlled apertures (velocity flame stoppers) allow the rise of these kinds of flame arresters as an alternative to standard static fixed element dry type flame arresters. This corild be especially risefnl in high flow applica-... 

Dry Type Flame Arrester A flame arrester that rises an element consisting of small gaps or apertures to quench and extinguish the flame, as distinguished from hydranlic flame arresters. 

Static Flame Arrester A flame arrester designed to prevent flame transmission by qnenching gaps (apertnres). These are nsnally dry type flame arresters with elements snch as crimped metal ribbon, parallel plates, wire ganze (mesh), and sintered metal. 

Dry type deflagration and detonation flame arresters have an internal arrester element (sometimes called a matrix) that quenches the flame and cools the products of combustion. A great number of arrester elements have been developed and used. The most common types currently available are as follows ... 

Other types of deflagration and detonation flame arresters that do not contain an arrester element (matrix) have been used snccessfnlly in various applications where conventional dry type arresters were not suitable or were very expensive. Among these are ... 

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. 

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