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Welding Galvanized Piping

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AdamMurray

Mechanical
Dec 23, 2003
18
Is it ok to weld schedule 10 galvanized piping on a dry pipe sprinkler system per NFPA 13? I would think not, but could not find any reference.
 
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no problem...just need to make sure that the welding does not affect the galvanizing....I typciall see fabricators apply a coating over the weld bead to prevent any problems.
 
2 doubts on this matter:

-What about the welding fittings?.
I mean, for example: I have a galvanized pipe welded to a butt welding fitting (like ASTM A234 tes or ellbow, and I think it is not a standard to have galvanized fittings, please clarify me if not).

-If the welding is a butt weld of two galvanized pipes. How can I apply a coating to the bead internally?.

In this cases, would you have a galvanic couple situation that would promote the formation of a local corrosion problem?
 
David,

I think Adam is talking about a welded outlet on the dry system main. It is done quite frequently. I know that doesn't always make it ok, but I have yet to hear of problems in dry systems where the outlet is welded to the main....maybe I have just been lucky..
 
As david has said, I am talking about welded outlets on the mains. Thanks for the comments guys.
 
Because galvanizing is a process to cover black steel pipes most kind of welding cause to "burn" galvanized layer and once it damaged corrosion is a matter of time. But there is also welding type which doesnt affect the galvanize layer so be sure you use the correct type of welding.
 
ercanbaser,

I'm not aware of any welding proceedures that wouldn't disturb the galvanize, could you fill me in?
 
The weld will not have a zinc coating but may be painted with zinc paint. You won't be able to coat the weld on the inside of the pipe, but zinc offers some protection from corrosion by imparting a negative charge on the steel.
 
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