By definition, a flame arrester is a passive device that allows gas to pass through it but stops the propagation of a flame.
The first flame arrester was invented by Sir Humphrey Davy in 1815 to protect miners from explosions caused by using naked flames in mines. The Davy lamp housed a candle within a fine gauze mesh screen which allowed light to pass through it whilst preventing flames from ignited pockets of methane escaping from the lamp. The mesh acted as a heat sink; cooling the flame and preventing it from igniting gas on the outside of the lamp.
Things have moved on since then, of course! Today, Elmac is one of the UK’s leading companies in providing the safe installation, inspection and maintenance of flame arresters. And we’d be happy to show you how.
Flame arresters: element design
The quenching mechanism of MESG is the principal on which flame arrester elements are designed.
Flame arrester elements are made up from a matrix of channels. The height and length of these channels is tuned offering the least resistance to gas flow whilst still quenching a flame.
There are a variety of element designs available in the market today with the most common being crimped ribbon. The main thing to remember is that the quench gap of an element will be different to the MESG of the explosion group it is certified for. Contact us to find out more.
Types of flame arrester
The flame arrester element is made up of a matrix of channels the walls of which quench the flame as it passes through by removing heat energy from the reaction.
Most flame arresters fall into two major categories:
- End of line, vent to atmosphere arresters – to prevent an atmospheric fire or explosion from entering an enclosure.
- In-Line – to prevent the propagation of an explosion within a pipeline.
Therefore, the main types of flame arresters Elmac supply, to all kinds of industrial businesses across the world are: end-of-line deflagration, in-line deflagration and in-line detonation.
All meet current legislation and standards: ATEX: Atmospheres Explosive – European Directive 94/9/EC covering all equipment used in zoned areas including flame arresters; EN ISO 16852: International standard to which flame arresters are tested. Current edition EN ISO 16852:2014
Flame arresters – deflagration and detonation
Deflagration and detonation refer to separate phases of pipeline explosions.
When the gas is ignited the flame begins to accelerate. This acceleration results in the build-up of a pressure wave ahead of the flame. Given enough run up distance, this pressure wave can build into a shock wave as the flame speed reaches sonic velocity. This first phase is known as a deflagration.
Once the shock wave reaches a pressure to auto-ignite the gas through which it is travelling the flame front and shock wave couple together forming an unstable detonation. This deflagration to detonation transition (DDT) is the most severe phase of a pipeline explosion, which can generate flame speeds of >3000m/s and high pressures, over 100bar in some cases.
In short, the deflagration flame arrestor is designed to stop the initial phase of the explosion and is shorter and lighter than the unstable detonation arrestor, but the deflagration flame arrestor has restrictions on its placement within the pipework regarding distance from the source of ignition.