General Information

What is backfire?

Backfire is the momentary retrogression of the flame into the torch that is usually signaled by a popping sound. The flame may either extinguish or re-ignite at the end of the tip. Sustained backfire (flashback) is the retrogression of flame into the torch with continued burning inside the torch. This event can be identified by an initial popping sound followed by a squealing or hissing sound caused by continued burning inside the torch. When it occurs, the torch oxygen valve should be turned off immediately and then the fuel gas valve.

What is flashback?

Flashback is the return of the flame through the torch and into the hose and/or regulator and can potentially cause an explosion at any point in the system. It may also reach the cylinder. This event is caused by oxygen and fuel mixing in one side of the oxy-fuel system and subsequently being ignited at the tip and by reverse flow of one gas into the other side of the system. When it occurs, the torch oxygen valve should be turned off immediately and then the fuel gas valve.

What if backfire continues to happen?

If backfire continues to occur, the torch or the tips, or both, should be removed from service for cleaning or possible repair.

Before you light your tip…

Ensure you purge all of your hoses and torch passages by briefly opening and closing each torch valve.

NOTE: Mixed gases in the torch or the hose, etc. can cause a backfire or flashback. Purging must be done before each torch lighting and especially after a cylinder change.

About flame heating.

Flame heating involves igniting fuel gases mixed with air or oxygen. Examples include flame straightening, flame hardening, hot forming and heating in conjunction with welding. The flame is used for melting purposes in flame brazing. Acetylene, propane, propylene, and natural gas are used as fuel gases for flame heating. The flame temperature and intensity depend on the fuel gases used and oxygen mixing ratio.

Clean your work area.

The immediate work area must be clean from all contaminants. This includes removal of dirt, grease, oil, rust, paint, plastic coverings, etc., from the surface of the parts being welded. The method of cleaning depends on the material to be removed and the location of the work piece. For most construction and production equipment, steam cleaning is recommended. When this is not possible, solvent cleaning can be used. Blast cleaning with abrasives is also used. For small parts, pickling or solvent dip cleaning can be used and, finally, power tool cleaning with brushes, grinding wheels, disc grinding, etc., can be employed. The time spent cleaning a weld repair area will pay off in the long run. Be sure that all solvents have been removed before applying heat.

How should I light my torch?

The most widely accepted manner to light the torch is to open the fuel gas valve slightly and ignite the gas with a spark lighter. Adjust the gas until a stable flame is maintained at the end of the tip. Open the oxygen preheat valve slowly and increase the flow until the desired flame is achieved.

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