The purpose of this article is to present a basic understanding of flames, flame arresters, and the multitudinous designs of flame arresters to help an Emergency Relief System (ERS) designer in selecting an appropriate flame arrester. The need to understand the characteristics of the flammable system and appropriate testing is presented. Various prominent manufacturers of flame arresters are presented and a recommendation to select the final product is also presented. After having the basic understanding of flame propagation and flame arresters, one has to define the scope of application. This article addresses the application of overpressure protection of near atmospheric or low pressure equipment and interconnecting piping header of equipment from flame-related deflagration and detonation. The generation of the property of a flammable mixture using various Maximum Experimental Safe Gap (MESG) apparatuses differs widely. So, the reader is advised to be informed: Application of flame arresters is deceptively simple!
Overpressure protection from flame-related deflagration of low pressure equipment, such as baghouse and pressure vessel, are beyond the scope of this article.
A flame is a physical manifestation of the combustion process in the visible spectrum of light or luminous intensity. It can happen when a flammable or combustible substance is in contact with an oxidizer in the presence of an ignition source as in the case of an open pool fire or at the exit of a vent from equipment containing a flammable vapor.
There are some flammable materials which do not need an oxidizer to decompose and generate a flame. It can also happen similarly inside a confined environment such as piping, storage vessel, and process equipment. Flame arresters prevent the overpressure effects from these scenarios.
This paper addresses the aspect of flame propagation and protection of equipment from the effects of internal combustion process by a judicious application of equipment known as the flame arresters. The effect of flame propagation inside confined equipment is more devastating than that of external fire because the former has both temperature and accelerating pressure effect on the containment. Standards of flame arresters are shown in Tables 1A & 1B. The name "Flame Arrester" is a generic name for devices that allow flow of gas, but are impermeable to any flame, and is used to protect equipment from overpressure caused by internal flames.
Figure 9: Decision Tree 1: Need for conservation vent, flame arrester or both, emergency vent due to fire for combustible and flammable materials.
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