Best black iron jointing method

Seen a large steam installation once. Nothing but ptfe used on joints from 1 inch right up to 3 inch . Apparently the boss white and hemp burns out at high temperature. Regards r2d2.

 

with gas, I would cut the thread a little tighter and use just jointing compound, as has been said hemp can not be used on gas.

 

You could just use gas compond but not a guaranteed joint, over a long run it could also fail with vibration and expansion.

In this case I will be using welded flanges on the 3" and locktite string on the 2" down

 

Doital i hope you dont have to cut the threads by hand like i did as a lad, we had a set of Bridges adjustable dies, would not like dto do it now.

 

no; will be using a Rigid threading machine, done my share with the old hand dies lol not about to start again

 

hawkwhite is ok on (natural) gas by itself, like i say for domestic, not sure about big stuff 2" plus...

LPG requires a different, but similar/thicker compound, such as calortex (think thats whats its called!)