The reason for using a protective device such as a Flash Back Arrestor on a fuel gas line or even on a cylinder are as follows:
1. Safety of property and human lives.
2. The flashback occurs under various conditions.
3. The flashback occurs inside the pipeline or vessels.
4. The flame moves through a vessel or pipe.
5. The flame velocity increases as it moves through these pipe or vessels, and if the pipe is long enough the velocity can increase to detonation levels, which are supersonic.
Where should a Flashback Arrestor be placed?
The flashback arrestor should be placed at the closest point to the flame, if due to unavoidable circumstances the Arrestor can not be places close to the cutting nozzle or the flame then it should be placed of the main pipe line, and also on the fuel gas bank, vessel, cylinder.
How does a flashback Arrestor works?
Flashback arrestor is a simple devise, which quenches the flame using the following methods
- By reducing the velocity of the flame, reducing the flame velocity even lower than the minimum flame velocity of the fuel gas.
- Stops the flame propagation into or through a pipe. By placing a flame arrestor at the end of the flammable mixture pipe feeding a flare or burner, flame can be prevented from moving into the pipe regardless of the mixture velocity.
- By passing a potentially flammable mixture through a water chamber or some sort of heat sink. This dissipates the heat and quenches the flashback.
- By blocking the fuel gas path, with a suitable thermal fuse plug, casing the flashback to die out.
- By blocking the flow of fuel gas in the opposite direction by acting like a non return valve.