Sealing black iron pipe joints

[Bustawrench]

all of our piping above 2" for steam is all welded and flanged connections. Everything above 3/4" for ammonia is welded.

That's the best way, IMHO.

 

[shooting4life]

got to go with the blue monster

 

[Sureshot]

Local plumber showed me that he uses silicone. It acts as a lube then sets up. Seems to work real good the few times I used it.

 

[ez-duzit]

One issue with silicone is that it does not like to stick to itself.