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What is the most common material gas pipes made of? I read in a unreliable website it's steel, is it true?

Also how good is steel at stopping or slowing down the leaking of gas?

The gas I am using or planning on using is Argon which is denser than air.

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In my admittedly limited experience working with plumbers, natural gas pipes are typically made from galvanized steel for interior work, or from black steel pipe for underground. Last-leg fittings and tubes which connect the stub-outs to various appliances are sometimes made from copper and brass. Other materials are possible, as noted here. Some things to consider:

  • When joining two pipes made from dissimilar metals (including steel and cast iron), always use a dielectric union to decrease the risk of galvanic corrosion between the two metals.
  • In US jurisdictions, exterior pipes must be painted to reduce the risk and rate of weathering.
  • In the US, natural gas typically contains a small amount of methyl or ethyl mercaptan. The additive has a foul smell which makes leaks readily detectible by most people. These compounds contain sulfur and will react with copper to form copper sulfide, eventually corroding through the pipe. Some copper pipes of types K and L are approved for use with gas. Only properly approved copper pipes should be used with natural gas, with appropriate fittings.

For argon, the first point is still relevant, though the last is likely irrelevant if the argon is pure. The second point may be relevant if you need any pipe runs outdoors.

As for leaking, the pipes themselves should not leak, typically it is joints that leak. If you need high pressure, ensure that the schedule of your pipe is sufficiently high (i.e. wall thickness) and that it is rated for the required pressure. As with all pressure vessels, ensure you have appropriate mechanical safety valves and a pressure regulator to decrease the risk of explosion. If you are worried about diffusion through the pipe, unless you plan to heat the argon to many hundreds of degrees C (which you will need specialized pipe for), the diffusion rates will probably be trivial. Focus on the pipe joints first for leak reduction.

If you only need to transport small quantities of argon over short distances, as in a lab setting, copper and brass flare fittings are most likely sufficient if the pressures aren't too high. If you need to transport large quantities, you should consult an professional engineer.

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  • $\begingroup$ Well the gas will be exposed to very hot environment, around 100°c-150°c and that's maybe minimum. What specialized pipes are there? I have a cooling system but still want to make sure the gas don't get to pressurized. $\endgroup$ – LostPecti Jun 28 '16 at 0:27
  • $\begingroup$ 100 to 150 C probably won't cause much worry for steel or copper, nor the fittings, and should be ok with teflon tape at the joints. You may want to look into high-temperature joint compounds though (I am unfamiliar with such things myself), as the more typical joint compounds might become too fluid and increase risk of leaks. I would recommend chatting with a plumber if you can find one who will open up, to get a more specific opinion. $\endgroup$ – wwarriner Jun 28 '16 at 1:23
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What is the context of your question? You are asking about natural gas but then mention argon. Natural gas and argon are very different substances with different uses.

The answer depends a lot on your environment, the composition of the natural gas, and the operating pressure. Most old natural gas pipelines were made with steel. However, steel pipelines are prone to corrosion and must have some kind of corrosion mitigation program in place (eg. pigging, chemical injection, etc.) This doesn't really apply if the pipe has an internal lining. Polyethylene is popular for lower pressure natural gas because it doesn't experience the same kind of corrosion problems steel does. However, it doesn't have the same kind of mechanical strength as steel.

If your pipeline is leaking I don't think it really matters what material you've chosen; it is leaking and the material isn't going to make it better or mitigate it. There is no such pipeline that will seal itself and stop the leak. Pipelines are also not porous enough that your process fluid would slowly seep out of it. If a pipe has been compromised enough to be leaking, the only way to stop the leak is to repair or replace the pipe. You should think more about what material and operating practices would prevent a leak from occurring in the first place; not about what material might slow or stop the leak once it has occurred.

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  • $\begingroup$ I do apologized that my question was unclear. I wasn't talking about natural gas in it self just the material use to transport it. The gas I need to hold is Argon gas. I am not sure but I believe argon gas is more dense the natural gas. Also the no material is leaking. I am creating a container to hold the gas and need a material that can stop or slow gas diffusion. $\endgroup$ – LostPecti Jun 27 '16 at 22:39
  • $\begingroup$ You are right argon is about 2.7 times more dense than natural gas although I don't really think that matters here. Most compressed gas cylinders are made of either steel or aluminum. The amount of argon that could diffuse into solid metal would be negligible. The pressure you're keeping the argon at within the container is really the most important thing to consider in the design as that would determine the thickness required. $\endgroup$ – Jenny Lu Jun 27 '16 at 23:36
  • $\begingroup$ I see your point. But that's one of the biggest problems I am having. I need to keep the gas at a high pressure, but also need to allow the gas to expanded, and safety diffuse out. As the system will be in a very hot environment ( easily reach 100°- 150°c ) and there's a high change of the system getting smashed. So I need to have a system that isn't to pressure to allow the gas to expand in the heat but also not violently exploded in an accident. Could the gas be pressurized but still have a lot more room to to not exploded in a hot environment? $\endgroup$ – LostPecti Jun 27 '16 at 23:49
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    $\begingroup$ You don't design over-pressure protection by allow the fluid to diffuse out of the vessel's walls. All pressure vessels are protected by some kind of a relief valve or some other system design (eg. max compressor discharge). If the argon expands due to increases in temperature the relief valve would open and your vessel would not explode. I also think you might be overestimating how powerful this gas expansion might be at 150C but I really can't say unless you give numbers for pressure. If you designed an overly large vessel your argon would simply be at a lowered pressure when not hot. $\endgroup$ – Jenny Lu Jun 28 '16 at 0:40

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