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Copper and Black Iron Mixed


randynavarro
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Originally posted by randynavarro

Natural gas line to furnace.

Various copper nipples used in combo with typical black iron pipe.

Dissimilar metals, yes? Need di-electric union?

Di-electric union ok with natural gas?

Were they really copper nipples? I've never seen such a thing. Were they made up out of two threaded fittings soldered to a short piece of tubing? Surely they didn't try to thread a piece of copper tube?

Are you sure that you weren't looking at brass nipples?

That aside, I doubt that a copper-to-steel connection on a gas line would experience much of a reaction without a liquid to act as an electrolyte.

- Jim Katen, Oregon

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Originally posted by Jim Katen

Were they really copper nipples?

As far as I could tell. There were various lengths. IOW, to make the jogs they needed, they assembed an iron ninety, then off that, a 6" copper nipple, then another iron ninety, then another 3" nipple.

I've never seen such a thing. Were they made up out of two threaded fittings soldered to a short piece of tubing?

No.

Surely they didn't try to thread a piece of copper tube?

It appears so. The pieces were threaded at each end.

Are you sure that you weren't looking at brass nipples?

I'll say this, if they were brass they were the exact same color as typical type M copper.

That aside, I doubt that a copper-to-steel connection on a gas line would experience much of a reaction without a liquid to act as an electrolyte.

Sounds reasonable.

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I'm not sure about intermixing dissimilar metals in gas piping, but as I was looking around I found this interesting writeup on using copper for gas lines.

http://www.copper.org/applications/fuel ... intro.html

This site has a lot of info on using copper for gas supply.

http://www.copper.org/applications/fuel ... fig03.html

Show proper connections from steel to copper.

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As Jim pointed out, for galvanic corrosion to occur an electrolyte must be present. Therefore, joining dissimilar metals to construct a fuel gas line probably wouldn't be an issue unless the utility is delivering gas with a high moisture content, something they try to avoid.

As for using copper in natural gas lines, it depends on the sulfur content of the gas. Here in Colorado the natural gas we use has more than the maximum 0.3 grains of hydrogen sulfide per 100 standard cubic feet of gas allowed under G2414.5.2 of the 2000 IRC. Therefore, the use of copper piping or tubing for natural gas lines is expressly prohibited. On the other hand, in Minnesota it's common to see copper tubing used for natural gas.

Here's what a quick search of the 2000 IRC yielded:

Section 2414.5 of the 2000 IRC states:

"Metallic tubing. Seamless copper, aluminum alloy or steel tubing shall be permitted to be used with gases not corrosive to such material."

Section G2414.10.4 of the 2000 IRC states:

"Metallic fittings. Metallic fittings, including valves, strainers and filters shall comply with the following:

1. Fittings used with steel or wrought-iron pipe shall be steel, brass, bronze, malleable iron, ductile iron or cast-iron.

2. Fittings used with copper or brass shall be copper, brass or bronze.

3. Cast-iron bushings shall be prohibited.

4. Special fittings. Fittings such as couplings, proprietary-type joints, saddle tees, gland-type compression fittings and flared, flareless or compression-type tubing fittings shall be: used within the fitting manufacturer's pressure-temperature recommendations; used within the service conditions anticipated with respect to vibration, fatigue, thermal expansion or contraction; installed or braced to prevent separation of the joint by gas pressure or external physical damage; and shall be approved."

I could find nothing that specifically addressed the connection of dissimilar metals with regard to galvanic corrosion.

As to the the definition of "nipple, I found the following:

The 2000 edition of the Means Illustrated Construction Dictionary defines "nipple" as: "A piece of pipe less than 12 inches long and threaded on both ends. Pipe over 12 inches long is regarded as a cut measure."

The Construction Glossary by J. Stewart Stein defines "nipple" as: "Short length of pipe (under 12 in.) with male threads on both ends for joining fittings."

Kevin

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Originally posted by housewhisperer

As to the the definition of "nipple, I found the following:

The 2000 edition of the Means Illustrated Construction Dictionary defines "nipple" as: "A piece of pipe less than 12 inches long and threaded on both ends. Pipe over 12 inches long is regarded as a cut measure."

The Construction Glossary by J. Stewart Stein defines "nipple" as: "Short length of pipe (under 12 in.) with male threads on both ends for joining fittings."

Kevin

Cool. I've finally been thinking right about something all these years!!

Thanks for the post Kevin - much appreciated. I know I could have easily referenced these resources as well, however I will confess to a weak trait of my maleness - laziness.

Kind of like my wife; why should I look for something when I can just ask her where it is and save myself the trouble!!??

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