Pipe sizing conundrum....

[Blumper]

It's density in relation to air is determined, as everything else is, by gravity, therefore it is always lighter than air, (0.6 relative density) whether it is trapped within a pipe or in the open air..... and as for it going vertically downwards, it would have to be subject to pressure to force it against its inclination to rise naturally......

 

[Howsie]

It's density in relation to air is determined, as everything else is, by gravity, therefore it is always lighter than air, (0.6 relative density) whether it is trapped within a pipe or in the open air..... and as for it going vertically downwards, it would have to be subject to pressure to force it against its inclination to rise naturally......

I'm still dubious because it's not relative in the pipe as there is no air in there. /scratch head.

 

[Blumper]

Think of it like this then Howsie, ..........Helium has a specific gravity of 0.13 (Air taken as 1.0)..if you fill a balloon with Helium, it floats, .......and the Helium is trapped in the balloon with no air in there with it just like gas in a pipe, so like gas, because it is lighter than air, it rises regardless.............

 

[Mike Jackson]

That analogy doesn't follow because the gas pipe isn't floating away. When you initially install the pipe if you allow some gas into it the gas will rise and displace the air. Once the pipe is full of gas the contents of the pipe all have the same relative density so it will not rise. It doesn't matter if pipework is vertical horizontal or corkscrew the resistance for a set length is the same so the pressure loss will be the same.