Technology is developing fast, and while innovation is taking centre stage, versatility remains right up on the checklists of both manufacturers and end users alike. With that in mind, the new Protectoseal Series 26000E/36000E bi-directional overdriven/unstable detonation arresters, now available in southern Africa through Energas Technologies, which usher in a new era in flame arrester technology with their versatility, allowing them to withstand both deflagration and detonation flame fronts.
Deflagration and detonation are two forms of combustion. If the combustion process propagates outward at subsonic speeds and pressures less than 0,5 bar, it’s a deflagration. If the explosion moves outward at or above the speed of sound it is a detonation, a dramatic, often destructive form of an explosion. Detonation is divided into two types: stable and unstable. Stable detonation is characterised by the speed of sound (343 m/s), while unstable detonation is characterised by supersonic speeds up to 2 000 m/s, with significant overpressure of up to 40 bar. In piping applications, selecting the right flame arrester, whether for deflagration or detonation, often involves the trouble of determining the probable type of combustion, location and other factors.
“The beauty of our new series detonation arresters is that the flow and pressure drop performance for these units are extremely competitive compared to other devices,” says Lavenda Sekwadi, process engineer, Energas. “Protectoseal’s Series 26000E/36000E detonation flame arresters are designed to withstand deflagrations as well as stable and overdriven/unstable detonations. These arresters are bi-directional, capable of stopping a flame or detonation approaching from either direction of a piping system. Available sizes range from DN50 to DN300, and the new range has a maximum operating pressure of 1,22 bar and operating temperature of 60°C.”
Features in detail
The Series 26000E/36000E detonation flame arrester designs utilise improved-flow, crimped metal flame arrester elements. The range comes with a robust welded housing, both hydrostatically and pneumatically tested. All detonation arresters are suitable for short-time burn when additional external safety equipment is properly used in accordance with the requirements of EN ISO 16852. Short-time burn arresters are equipped with two FNPT taps for the installation of ATEX-approved IS temperature probe assemblies. The probes are used to detect a burn on the flame arrester element and send a signal that will trigger emergency functions within a specified time.
Stable vs. unstable detonation arresters
Unstable detonation arresters are required for safety in piping containing flammable vapours, as encountered in vapour recovery or manifold tank systems. “A confined flame front will accelerate from the point of ignition, quickly reaching the speed of sound in the pipe run,” concludes Sekwadi. “During the unavoidable transition period from subsonic to supersonic speeds, flame front pressures and velocities are far greater than before or after the transition – an unstable detonation.
“Devices approved under ISO 16852 as ‘stable detonation arresters’ have not been tested against the severe mechanical and thermal effects of multiple unstable detonations. The use of stable detonation arresters is based on the premise that, firstly, it is unlikely that the unavoidable high pressure and velocity transition will occur as the flame front reaches the detonation arrester, and secondly, all of the independent safety systems required to be installed when stable detonation arresters are used will function as required.”
For more information contact Lavenda Sekwadi, Energas Technologies, +27 (0)11 397 6809, [email protected], www.energas.co.za
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