Actual Difference….

busman said:
This was probably 20 years ago, but I remember my Plumber friend (Licensed Journeyman Plumber) said that galvanized pipe could not be used for gas because the galvanizing on the threads could impede the gas seal, even with dope.
Click to expand...
My understanding is that when natural gas systems carry gas with a significant sulfur content, the zinc coating can react to make ZnS, which can form fine particles carried in the gas that can plug orifices in burners. But most (all?) modern natural gas systems now carry low sulfur gas, so the concern is reduced and it's fine to use galvanized for natural gas.

Cheers, Wayne
 
We had a big pipe mill at USX Fairless Works. I was there a bunch of times. The pipe has a longitudinal weld seam. They shave (scarfing process) the outside of the plumbing pipe smooth, but there is usually a sharp seam left on the inside.

Electrical conduit gets a better scarfing on the ID

BTW, the scarfing makes for some nasty scrap. Like razor wire. I had a friend get cut up bad when a crane op grabbed the other side of a pile that he was next to and a long piece pulled everything
 
busman said:
I did a bit of online research. It appears that galvanized is NOT recommended for pluming due to poor corrosion resistance and the possibility of the galvanizing flaking off and clogging lines. Strangely, Black Iron is considered more corrosion resistant due to the coating and the low carbon composition. Learn something new everyday.

Mark
Click to expand...
That is all false.
 
busman said:
This was probably 20 years ago, but I remember my Plumber friend (Licensed Journeyman Plumber) said that galvanized pipe could not be used for gas because the galvanizing on the threads could impede the gas seal, even with dope. He said you had to use black iron, as its threads are bare steel. I have no opinion on the validity of this, but this thread had me curious.

Mark
Click to expand...
Don't know where he is located but most national codes allow galvanized for gas and some states like NJ are near the ocean and require it. I live in MA. and am a licensed gas fitter. MA does not (and never has) allow galvanized pipe use on gas
 
ptonsparky said:
Could be. I know we weren't supposed to use it with propane and worked with enough plumbers at the time to know it wasn't allowed by them.
Click to expand...
I've used it with propane and NG plenty and also disassembled it after having been in service for the greater fraction of a century. There is no deterioration of the inside, zero. There is no code anybody has been able to show that disallows it.

It all looks the same with a coat of paint anyway.
 
The black pipe and fittings installed for gas is not black iron. It the same steel pipe as the galvanized but has a paint coating instead of galvanized.

I have heard the same thing about the galvanized coating flaking off but galvanized pipe has been installed for gas for al long as I remember. Maybe it was a problem at one time and is related to Wayne's comment above.

When I built my house about 6 years ago I ran about 300' feet of gas pipe, from 1/2" to 2". I used mostly black pipe since it was slightly cheaper. All fitting were galvanized since the supply house carries a better selection of galvanized fittings.
 
The pipe is mostly common steel and most fittings are forged. There are some cast versions, cant remember it all but both have bit higher carbon I believe which gives them strength but sacrifices ductility. They will weld but not reliable without special precautions.
 
Sberry said:
The pipe is mostly common steel and most fittings are forged. There are some cast versions, cant remember it all but both have bit higher carbon I believe which gives them strength but sacrifices ductility. They will weld but not reliable without special precautions.
Click to expand...
Standard gas fittings are something called malleable iron. It is cast to make them. Only high pressure fittings are forged. I don't know what malleable iron actually is. I don't think it is used in any other common application any more.
 
I've always heard that galvanized shouldn't be used for diesel or gasoline. I never used it for either. Black iron is cheaper anyway.

Back in the day I used to find galvanized used for a lot of water piping before copper became popular. It was never a problem with sealing. Most times I've had to cut it out because it was restricted with scale and mineral deposits
 
Malleable iron is a form of cast iron which has been heat treated to lower the carbon content somewhat and make the sheets of carbon form tiny graphite spheres - that make it tougher and more shock resistant. Ductile iron is similar but usually produced by adding ferro-silicon to the melt. Some folks consider them interchangeable materials and names but they are slightly different.
 
We had two mills along the delaware that made ductile pipe just north of the Burlington Bristol Bridge. US Pipe and Griffin Pipe. US took 5' P&S and Griffin 3 foot.

Here are the specs

Core Specifications for P&S Steel
Regardless of length, the following core quality standards applied (and still apply):
  • Minimum Thickness: Must be at least 1/4 inch thick.
  • Composition: Must be clean, "alloy-free" steel. Acceptable items include steel plates, structural shapes (beams, channels, angles), crop ends, and shearings.
  • Chemical Limits: Phosphorus or sulfur content must not exceed 0.05%.
  • Excluded Items: Generally excludes rebar, cast iron, pipe (unless split), and anything with non-metallic attachments or excessive rust.
Click to expand...

That was all the scrap they were taking and it was pretty pricy stuff. The defective pipe cut funny when we chopped it back up in a 925 Harris and shipped it back. As it was cut, it would start shearing, and then fracture pretty quick.
 
Birken Vogt said:
Gas stations that I have observed are all galvanized pipes running everywhere.
Click to expand...
I originally heard that from G&R Cat (Our local cat dealer) back in the 80's. If I remember right they told me about installations where galvanized was used to run from the bulk tank to the day tank and it messed up the float in the day tank for the transfer pump.

Then again, that same shop insisted on covering exhaust stacks during transport because they said that the wind during transport would cause the turbos to spin backwards and burn up because of no oil.

Makes you wonder about the credibility of anything they said
 
You must log in or register to reply here.
Top