Every year hundreds of welders are seriously injured as a result of improperly using an oxy-acetylene torch. Oxy-acetylene torches are primarily used in the cutting, welding, brazing and heating of metals. The majority of the equipment in use today is relatively safe, but if they are used improperly that is where the danger can occur.
One of the major causes of fires and explosions is high acetylene pressure. If more than 15 pounds of pressure is used, acetylene becomes volatile and can result in explosions. This instability is why many have begun to use propylene, propane and natural gas. These gases can be used safely if the process requires higher operating pressures.
Using an oxygen cylinder that is low or empty may cause a reverse flow of gas. Because the fuel gas is at a higher pressure, it may travel up the oxygen line and mix with the gas in the hose, regulator and cylinder. If you then light your torch without purging the line you may experience a burn back with explosions in the hose, regulator or cylinder.
Backfire occurs when the cutting torch is too close to your work. This will cause the cutting flame to be deprived of gas and will result in the flame being sucked into the torch head. A warning of this happening is a popping or whistle coming from your torch. If you hear those warning sounds it is important to shut everything down and purge the lines.
If a backfire occurs in a mixing chamber the flame burning in the torch head may cause the gases to ignite in the hoses and result in a flashback. Flashback is an explosion that travels through the torch, hoses, regulators and cylinders. This is a very dangerous situation and can cause a burst hose or a more hazardous explosion of the regulator or cylinder.
Oxy-acetylene Welding and Flashback Resources
The Beginners Guide to Oxy-Acetylene Welding Equipment (www.metalwebnews.com)
Oxy-fuel Welding and Cutting (www.wikipedia.org)