I have heard that you can convert acetylene welding setups to propane. please explain how?

Answer 1

You should change the gas system, that is cylinders, pressure reducers and probably hoses.Probably the torch should be adapted. The oxygen part remains the same.The oxyacetilenic is relatively hotter but on some soft soldering propane is better.

Answer 2

[edit] Propane
Propane does not burn as hot as acetylene in its inner cone, and so cannot be used for welding. Propane, however, has a very high number of BTUs per cubic feet in its outer cone, and so with the right torch (injector style) can make a faster and cleaner cut than acetylene, and is much more useful for heating and bending than acetylene.

Propane is cheaper than acetylene and easier to transport.

Like propylene, most propane tips are of a two piece design. Propane often gets unfair criticism because it really needs changing your torch (from an equal pressure torch to an injector torch) and not just changing your tip to get the best performance. Most torches are equal pressure and designed for gases such as acetylene which are lighter than oxygen. Propane is a great deal heavier and runs much better through a low-pressure injector torch with a setting from a few ounces to about two pounds per square inch when cutting.