Posted by Vern on May 30, 2001 at 12:32:42:
In Reply to: Re: Galvanized Pipe in Blowoff-Blowdown Systems posted by Chris Davies on May 30, 2001 at 09:03:14:
: : What is the reason that galvanized pipe is not permitted in Boiler Blowoff and Blowdown systems ?
: : (See ASME B31.1 "Power Piping Code" para. 122.1.4 )
: : Is the reason because the zinc coating will pose a health hazard as it degrades due to high temperature or is there another reason ?
: : Thanks in advance !!
: : MJC
I believe the reason has to do with electrolysis. The two dissimilar metals set up a galvanic
reaction, and the galvanized pipe is slowly eaten away, reducing the strength. I don't know if that
is the reason the code people have, but is what I was told by an inspector about
20 years ago. There may be other reasons. Here in California, the only place you can use
galvanized pipe is for the makeup water line to the feedwater tank. Every other pipe has
to be black iron.
:
: I'm not sure about the galvanized restriction, but you will need scd 80 pipe up to the second BB valve.