Just a word of caution about heating SS kegs heated with direct flames such as LPG burners and other fuels such as wood.
Kegs and the SS alloy used were deigned for Beer storage and freighting it, not for use as a boiler.
If the SS is overheated, it can severly affect the metal, especially the base ring of a keg. Never let the base ring get too hot. Continual over heating may cause what is called granular corrosion at the weld boundaries where the base ring is welded to the body of the keg, as well as destroying or severly reducing the corrosion resistance of the heat affected metal in the base ring.
If the base ring has a deep blue colour where flames have been impinging on it, it has been overheated.
Cheers, Icarus