1) What does the term “Alternate Fuel Gas” mean?
In the welding industry the term “alternate fuel gas” refers to gases other than acetylene. This term is typically used when referring to Natural Gas, Propane or Propylene based fuels used for oxy fuel torch applications.

2) What does the term “LP Gas” mean?
LP gas is referred to as “Liquefied Petroleum”

3) What is the difference between Acetylene & LP gas for oxy-fuel cutting?
Both types of gases are used to preheat steel for cutting. Acetylene produces a higher concentration of heat in a small area located at the end of the preheat flames, whereas the heat produced by LP gases is spread throughout the outer flame.  Both gas types work well for cutting, however each has it’s benefits for certain cutting applications.  Acetylene typically provides faster preheating to start cuts and for piercing, whereas LP gases provide some advantages when cutting stacked materials or for cutting very thick steel.

4) Do I handle the torch differently when using alternate fuel gas for cutting?
Yes, adjusting the preheat flames is quite different when using alternate fuels.  The preheat flames must be worked up in order to force a high volume of fuel gas out of the tip.  Insufficient gas flow will result in starving the tip, causing the flame to burn slightly inside the tip, which In turn will cause the tip to over-heat.  Forcing the fuel is accomplished by repetitiously opening the torch fuel valve followed by the oxygen valve to work up the flame.  Once the flame has been adjusted to provide a strong gas flow, oxygen is added for the final time to produce a neutral flame.  This is accomplished by adding additional oxygen to the flame until the preheat cones are reduced to their shortest point.  Adding oxygen beyond that point will produce an undesirable oxidizing flame.  Also, due to the slower burning rate of alternate fuels it requires the torch to be positioned further away from the steel when preheating.  When using acetylene, the points of the preheat flames are typically positioned approximately 1/8”-1/4” away from the preheat surface as apposed to alternate fuel flames which should be positioned further away from the work piece, approximately ¼” to 5/8”.  This is due in part to the slower burning rate of alternate fuels.

5) How does LP gas compare to Acetylene for Piercing steel?
Due to the higher heat concentration produced by acetylene it will typically bring the surface of the steel to it’s combustible point faster than alternate fuels.

6) What is the difference between Acetylene & LP gas for gas welding?
An acetylene flame produces a higher concentration of heat in a smaller compact area compared to alternate fuels.  This is why it is possible to fusion weld with an oxy-acetylene.  An oxy-LP flame is not capable of gas fusion welding of steel because the heat produced is spread out in the flame.

7) How Far should an LP cylinder valve be opened for use?
An LP cylinder valve should be opened completely when in use.

8) What is the difference in LP & Acetylene tip construction?
An LP tip usually is constructed with a recess at the end of the tip (counter-bore).  This is due to the much slower burning rate of LP gas. The recess makes lighting and stabilizing the flame easier and makes the flame burn more efficiently.  The recess of a propane tip is usually slightly deeper than that of a propylene tip due to the fact that propylene burns faster than propane.  The outlet end of an acetylene tip is flat (flush), as acetylene is a very fast burning gas.  Acetylene should not be used in tips designed for alternate fuel gases, because it’s faster burning rate will allow it to burn down inside the LP tip recess resulting in overheating and destruction of the tip.

9) What is the difference between Acetylene & LP gas for heating?
Acetylene will provide a more localized heat due to the higher concentration of heat produced in the flame.  LP gas will provide a broader area of heating as the heat produced is spread throughout the outer flame.  Acetylene actually has a higher flame temperature (6000°F) than alternate fuels.  However, propane & propylene produce more heat energy which is measured in BTUs, British Thermal Units.  A (BTU) is the amount of heat energy needed to raise the temperature of one pound of water by one degree F.

10) Can I use an acetylene regulator on an LP cylinder?
An acetylene regulator will operate on an LP cylinder, however an LP regulator should never be used with acetylene.  This is due to the fact that acetylene should never be used at outlet pressures greater than 15 psi. and an LP regulator is capable of producing outlet pressures much greater than the maximum, safe, allowable acetylene outlet pressure of 15 psi.  Smith Equipment’s policy is that no regulator should be operated with gases other than those recommended for that specific model.

11) Are there any oxygen flow issues with Flashback Arrestors when using LP gas?
Alternate fuel tips require higher oxygen flow than acetylene for torch operations. Most standard sized fuel gas flashback arrestors will provide the necessary flows to accommodate even the largest tips, however some oxygen flash arrestor designs may not be capable of supplying the necessary oxygen flows needed to supply larger heating tips or cutting tips. This is especially true for cutting tips, due to the higher oxygen flow requirement needed to supply the cutting jet.  Greater consideration must be given to the flow capacity of the oxygen flashback arrestors when using LP gases with large torch tips. In some cases simply increasing the oxygen regulator outlet pressure may help to supply the necessary flow for the larger tips.

12) What do I need to do to convert my existing Smith equipment for use with LP gas?
With Smith torches you simply need to switch the tip for the gas used and replace the acetylene regulator with an LP gas regulator.  Also, you will need to switch from an “R” grade to a “T” grade hose. “T” grade hoses are built to resist breakdown from LP gases.

13) Can I use an acetylene style welding tip with LP gas for brazing or soldering?
LP gases may be used with an acetylene style welding tip, however the flame size will be diminished. Also, the flames are somewhat more difficult to ignite, stabilize and adjust.  To achieve similar brazing results when switching to LP gas it may be necessary to go to a larger tip.

14) What kind of hoses do I need when using Alternate fuels?
A “T” Grade hose is required for use with alternate fuels. The grade of the hose is usually marked on the side of the hose. “T” grade hoses are constructed with a material that is more resistant to deterioration by alternate fuels.

15) How large must my LP tank be to provide sufficient gas flow to operate the torch?
You must first determine the gas flow needed to support the tip being used. The gas flow needed for a tip is usually measured in cubic feet per hour or liters per minute. You can find gas flow rates for Smith tips on our website, catalog or in our operations manual. There are two main factors that determine the flow capability of an LP tank; the size of the tank and the surrounding air temperature. The attached table represents the flow capacity in cubic feet per hour for various tank sizes at various temperatures.