Flashback Arrestor

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Chapter : Gas & Oil Safety

Flashback Arrestor

A flashback arrestor is designed to contain a flashback and prevent it from penetrating into upstream equipment (i.e. hoses, regulators and gas cylinders). Flashback arrestors both quench the flame and close off the gas supply.

• A flashback arrestor is a safety device essential to protect personnel and workplace environment.
• It is most commonly used in oxy-fuel welding and cutting process. It is used to stop the flame or reverse back up of gas into equipment or supply line.
• It protects user and equipment from damage or explosion.
• A common flashback arrestor that we find in the industry is dry flashback arrestor.
• The flashback arrestors are suitable for fuel gases such as acetylene, hydrogen, methane, propane, propylene and butane as well as oxygen and compressed air.
• Flashback arrestors have to be tested for gas non-return, for tightness and for gas flow by a qualified person according to relevant regulations.

Flashback Arrestor helps to prevent 

• Gas flow in the case of pressure shocks. 
• The entry of air or oxygen into the distribution line or single cylinders. 
• Flashbacks which are the rapid propagation of a flame down the hose. 
• Gas flow in the event of a burnback.

Device Components

1. Pressure sensitive gas –cut off valve: The pressure-sensitive cut-off valve stops the gas flow in the event of pressure shocks. 
2. Gas non return valve: The gas non-return valve ensures the gas only flowing in the intended flow direction.
3. Flame Arrestor: The flame arrestor cools the flame down to below the ignition temperature. And also prevents flashback.
4. Thermal cut-off valve: The thermal cut-off valve closes automatically at a certain temperature and cuts off the gas flow.

Flame arrestor and gas non return valve are two minimum safety elements that must be the part of the device.

• A flashback can be caused by a variety of conditions such as
• Sustainedbackfire.
• Incorrect hose purging.
• Wrong gas pressure.
• Operator errors.
• When a flashbackoccurs the flame front and pressure wave retreat into theblowpipe and hose at a very high speed. This can cause detonation within thesystem.
• It is essential that the regulator and more particularly the cylinder areprotected from the effect of a flashback.