In process operations with combustible gases, flame arrestors are devices that help mitigate the risk of combustion. Wikipedia defines these devices:
I mention this because I saw a LinkedIn status update from Emerson’s Michael Calaway about an excellent technical primer on flame arrestor technology. This primer was developed by the team managing the Enardo brand of safety and environmental vapor control equipment and services.
I’ll highlight a few of the basics from the paper and encourage you to read the full paper which provides an introduction to the technology and terminology of flame arrestors and the types of flame arrestor technologies available.
The history of the technology dates back to 1815 in England. The challenge was:
…prevent miners’ oil lamps from causing explosions when flammable gas called firedamp seeped into the mine shafts.
Sir Humphry Davy, a chemist and inventor developed a solution:
…to enclose the lamp flame securely with a tall cylinder of finely woven wire screen called metal gauze.
The solution was based on the idea of the metal wire absorbing heat from the flame and radiating it away at a lower temperature to avoid combustion with the combustible methane gas in the mine.
Today, flame arrestors still operate on this principle:
…removing heat from the flame as it attempts to travel through narrow passages with walls of metal or other heat-conductive material.
Flame arrestor technology is widely used across the process industries:
…including refining, pharmaceutical, chemical, petrochemical, pulp and paper, oil exploration and production, sewage treatment, landfills, mining, power generation, and bulk liquids transportation.
Some processes which involve combustible or reactive gases include:
…blending, reacting, separation, mixing, drilling, and digesting. These processes involve numerous equipment configurations and gas mixtures.
Two types of flame arrestors include end-of-line, also known as vent to atmosphere and inline, deflagration (rapid burning) or detonation (explosion).
The end-of-line ones are often used in oilfield storage tanks to prevent the tank from exploding when gas flowing from the vents is struck by lightning.
Applications for in-line flame arrestors:
…are in systems which collect gases emitted by liquids and solids. These systems, commonly used in many industries, may be called vapor control systems. The gases which are vented to atmosphere or controlled via vapor control systems are typically flammable.
Flame arrestors are passive safety devices that:
…do not depend on a power source, have no moving parts, and do not require human attention except to be cleaned periodically.
They are sized based upon:
…the nature of the flame which is expected (especially how fast it moves) and on the expected intensity of the pressure pulse created by the flame.
There are 12 categories of flame arrestors based on the flame hazard (NEC Groups B, C, D), end of line or in-line, deflagration or detonation, and speed of the flame based on pressure.
The paper provides combustion basics around chemical reaction kinetics, air/gas ratios, flame propagation and development stages and the physics around deflagration and detonation conditions.
It highlights selection criteria based on gas velocities, operating pressures, flame stabilization and more.
Give it a read either for basic understanding of the technology or to select the right flame arrestor for your application.
You can also connect and interact with other pressure regulator experts in the Regulators group of the Emerson Exchange 365 community.