Propane and other liquefied petroleum (LP) gases are used in flame cutting. The maximum temperature of an oxypropane flame is approximately 2030°C (5300°F), and is achieved by using five volumes of tank oxygen to one volume of propane. This requires
about three times as much oxygen to produce the same amount of heat as with acetylene.
Advantagesof OxyLP Gas Cutting
In flame cutting, the function of the preheating flames of the cutting tips is to raise the temperature of the steel to the kindling temperature: cherry red or approximately 900°C (1650°F). At that temperature the steel will burn in a stream of air or oxygen. The oxyLP mixture will produce a very satisfactory cut, despite the fact that its flame temperature is lower than that of the oxyacetylene flame. This means that the time required to start a cut will be a few seconds longer than with acetylene.
Once a cut is started, there are a number of advantages of oxyLP gas. Because of its lower temperature flame, the edges of the cut are not overheated, and a narrower kerf is burned away. The smaller volume of metal removed requires less oxygen to oxidize the
metal. This minimizes the slag adherence to the underside of the kerf. If slag is present, it is easily removed. The lower preheat temperature does not melt down the top edges of the cut.
A special tip is required when LP gas is used with a standard flame cutting outfit. The torch, regulators, and hoses are the same as for oxyacetylene cutting. Backfiring, pre-ignition, and flashback are very rare with LP gas because of its slower burning characteristic.