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Alternative fuel is the term used in oxy-welding and oxy-cutting for gases that are used as substitutes for acetylene when cutting metal by mixing a combustible fuel with oxygen in order to cut, weld, or braze metal. The most common alternative fuels are natural gas, propane and propylene, but hydrogen and MAPP are also used for certain oxy-cutting applications.
Oxy-cutting combines a fuel with oxygen in order to produce a flame at a high temperature in order to heat up and cut metal. Acetylene and some alternative fuels such as HGX propane burn hot enough in order to weld. Most welders tend to use alternative fuels for cutting work.
Why Use Alternative Fuels
Acetylene has been a popular cutting and welding fuel because it burns at 5700 degrees F. This high temperature enables oxy-cutting operations to quickly heat up metal and cut it. The effectiveness of acetylene has made it hard to replace over the years. However, a shortage of acetylene in the United States has caused some to consider alternative fuels.
Besides the recent shortage of acetylene, there are several other reasons to consider alternative fuels:
- Acetylene is an unstable fuel that can be dangerous to store and use. Alternative fuels tend to be more stable and easier to store.
- Acetylene is a costly fuel that uses more oxygen than alternative fuels that are generally cheaper to use.
- Many cutting operations already have access to fuels such as propane. The cost savings offered by ease of supply makes such an alternative fuel preferable to acetylene.
Modifications for Alternative Fuels
When switching from acetylene to an alternative fuel, equipment modifications must be made for both optimal cutting performance and personal safety. Here are some of the changes that must be made in order to use alternative fuels:
- Cylinders: Alternative fuels will require different cylinders that will also use different valves.
- Regulators: Since alternative fuels are able to operate above 15 PSI, they will need different regulators that permit the correct range of pressure for cutting. Using the correct regulator will improve the heating process with alternative fuels.
- Hose: The best long-term solution for working with alternative fuels is a grade T hose. The R and RM hoses used for acetylene will deteriorate faster, creating safety hazards.
- Torch: Alternative fuels such as propane require a specially designed torch that will maximize the gas flow. Propane uses an injector torch that will allow the flame to burn much hotter than using an acetylene torch with propane.
- Cutting and Heating Tips: There are tips designed for alternative fuels that will also help alternative fuels reach optimal heating and cutting temperatures.
Propane is a common acetylene substitute for cutting operations, though it does not burn hot enough in order to be used for welding. The most important differences between acetylene and propane are that with propane the heat is concentrated on the tip of the flame and propane does not pre-heat metal as fast as acetylene. The flame for acetylene is concentrated on the inside of the flame. Welders accustomed to cutting with acetylene will need to modify their cutting techniques when switching to propane.
Propylene is an alternative fuel that is derived from propane and has many of the same characteristics as propane when used as a cutting fuel. It requires an injector torch and also concentrates its flame on the outer edge of the heat cone. The propylene torch tips provide eight holes in order to make it more effective for pre-heating.
A relatively new product, HGX propane (technically referred to as HGX-3) is an additive for propane that enables it to burn at 5400 degrees F, a temperature that is comparable to acetylene. This makes HGX propane quite similar in performance to acetylene without the same risks of flashbacks or spatter along the cut.
One gallon of HGX is added to 1,000 gallons of propane and uses less oxygen than acetylene. Much like other alternative fuels, HGX also requires specific components such as compatible tips and hoses.
When oxy-cutting with alternative fuels, it's important to wear face protection, flame resistant clothing, and welding gloves. Fuel tanks must be securely fastened in an upright position. Alternative fuels tend to be more stable than acetylene and do not cause the same kinds of flashbacks, but operators must still beware of leaks in their hoses and wear appropriate safety gear at all times.