SECTION 3 – ADDITIONAL SAFETY PRECAUTIONS. HobartWelders OXY-FUEL OUTFITS 770502, 770974

SECTION 3 – ADDITIONAL SAFETY PRECAUTIONS

3-1.

Hazardous Events

The following events are very hazardous and can occur in any oxy-fuel system. It is important to understand these hazards and know how to prevent them.

Backfire: The return of the flame into the torch, usually accompanied by a popping sound. The flame may be extinguished or it may re-appear at the tip end.

Sustained Backfire: The return of the flame into the torch that continues to burn inside the torch with a hissing or squealing sound.

Flashback: The return of a flame into and through the torch or into the hose. In some instances it can reach the regulator and even enter the cylinder. This is generally caused by the mixing of the oxygen and fuel gas in the system. This is a very dangerous situation that can cause

an explosion anywhere in the system. This is why purging is so important (see Sections 6-1 and 6-2).

3-2.

Associated Hazards Of Recompressing Pure Oxygen

Open oxygen cylinder valves slowly. Opening an oxygen cylinder valve quickly can cause a fire or explosion. Be sure regulator adjusting handle is in the full out (off) position before opening an oxygen cylinder valve.

Recompressing high pressure oxygen in a low pressure cavity may create heat, resulting in combustion. For combustion to occur, oxygen, fuel, and kindling temperatures must be present. All of these components may be present when oxygen is recompressed by opening the tank valve too quickly.

Oxygen: High purity oxygen accelerates the rate of combustion, increases heat output, and lowers the combustible point at which various materials will burn.

Fuel: The fuel for combustion may be the regulator itself if enough heat is produced to reach the kindling temperature of the regulator’s components.

Kindling Temperatures: Enough heat may be generated to ignite the regulator components by the friction created when recompressing high-pressure oxygen. This heat is known as the heat of recompression.

If an internal fire or flashback occurs (indicated by a whistling sound or inverted flame), do the following:

� Turn off the torch oxygen valve immediately.

� Turn off the torch fuel valve.

� Turn off the oxygen cylinder valve.

� Turn off the fuel gas cylinder valve.

Do not relight the torch until the equipment has cooled to the touch and the flashback cause has been determined and corrected.

3-3.

Inspecting The Equipment Before Use

Inspect all equipment before use. Do not use damaged, defective, or improperly adjusted welding and cutting equipment.

Make sure levers and valves work properly, threads on equipment are clean (no grease or oil) and not deformed, gauges are intact and easy to read, regulator is clean and free of oil or dirt, and fittings are properly sized for the cylinder. Make sure hoses are clean (no grease or oil) and ferrules are properly installed so the fitting does not slip inside the hose. Be sure all connections are tight and there are no leaks in the system.

This manual offers basic information regarding the Medium-Duty and Heavy-Duty Oxy-Acetylene Cutting and Welding Outfits. Given reasonable care, this equipment will provide trouble-free use for many years.

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