Propylene - information

Propylene (C3H6) is a colourless fuel gas with a naturally pungent smell. Although similar to propane, it has a double bond which gives it a combustion advantage. This fuel gas is extremely flammable and non-toxic. Propylene is obtained during the refining of petroleum and is an attractive alternative to propane for heating and cutting due to its superior combustion performance.

Propylene Pros
* More stable and safer than acetylene and no 15 psi limit on working pressures
* No soot
* More btu's of heat for heating large parts and thick metal
* Cuts metal quickly and with a very long tip to work distance
* Better heat transfer properties than acetylene
* No cylinder withdrawal rate limitations

and Cons
* Slight learning curve on lighting and setting the torch
* Does not create a shielding gas when using for welding. (Oxy/Acetylene neutral flame produces CO2 which shields weld puddle)
* Propane 'lined' hose should be used
* Propane cutting tips should be used
* Larger tip may be required

Propylene releases the majority of the heat in the Secondary flame which creates more of a soaking or quenching heat drawing in Oxygen from the surrounding air as opposed to the concentrated effect of the Acetylene flame where the heat is released in the Primary Flame (Cone) so although a disadvantage for welding this is an advantage for heating especially on large areas.

With cutting it is the stream of Oxygen which does the 'Cut' Fuel gases are merely for pre-heat.

When Brazing the distance between the face of the flame head and the work piece is called the 'Coupling Distance*'. The coupling distance for Acetylene is far smaller than that of Propylene therefore the Propylene flame allows far greater control over the Braze puddle.

* For any fuel gas the coupling distance depends on port velocity and port size* The distance for Propylene is between 5/16" & 7/8"

This information has been reproduced from various internet sources.