Listed is the kind reply from Andrew concerning Copper Tubing being used with natural gas.
Your question was: In our newsgroup, Alt.HVAC we are discussing the use of copper tubing being used for Natural gas. We know that it is allowed now, but this was not allowed until the early 80's. Use on propane however was permitted.
Why wasn't copper permitted until then for natural gas but was permitted to be used with propane?
What has changed since then?
Does copper or flake or not when exposed to Natural gas? I was always under the impression that natural gas wasn't as purely refined to remove sulfur to an acceptable level and probably the refining has improved, is this correct?
Thank you very much, and I hope you permit me to copy and paste your reply on the newsgroup or you may visit the discussion and answer it there under 'gas and copper fittings'.
Thank you very much
Response: Dear Rich,
Sorry for the delay in answering your inquiry.
While copper wasn't included as a recognized material in the National Fuel Gas Code until 1989, it was widely used for natural gas systems in various areas of the country. Areas such as the state of Minnesota, Birmingham, Alabama and surrounding areas, St. Lous, Missouri, and the Washington D.C. area. Most of the areas have successfully used copper for natural gas distribution for 40-plus years.
However, other areas of the country did not permit the use of copper in natural gas systems. The main reason being a difference in the quality of the natural gas being supplied. In those areas where copper was used successfully, their natural gas streams were either naturally low in hydrogen sulfide, or they processed their gas to remove hydrogen sulfide. In areas where the levels of hydrogen sulfide were high, they didn't allow the use of copper, or if they did use copper found that they would experience black flaking caused by the reaction of the hydrogen sulfide with the copper tube. In general, even in the worst systems reaction was not sufficient to cause failure of the piping system, but the flakes could result in nuisance service calls if they blocked burner orifices, valves etc. and resulted in a gas blockage.
As the natural gas industry has evolved, the treatment of gas streams to remove hydrogen sulfide gas has steadily improved, and requirements to control the level of hydrogen sulfide provided in gases either supplied to or taken from interstate pipelines has resulted in a reduction of hydrogen sulfide levels in most gas streams to levels that eliminate the flaking concerns previously encountered in copper systems.
As you had stated, this was never a problem with LP gas systems because the hydrogen sulfide levels in these "manufactured" gases were more tightly controlled.
As a result of the improvements in natural gas processing, the industry is now able to take advantage of the many benefits that copper has been offering for LP gas installations for many years.
I hope this answers your question and again I'm sorry for the delay. If you would like more information please feel free to contact me directly.
Best regards, Andrew G. Kireta Jr. National Program Manager Copper Development Association Inc. P.O. Box 940 Franklin, IN 46131 phone: 317.346.6442 e-mail: email@example.com
Your contact for this case is: Andy Kireta Jr.