Why does the LPG cylinder has to be two parts welded together

[pbaero222]

Am a second year be student.While in a discussion in class my professor posed this question to us"Why does the LPG cylinder has to be two parts welded together".I tried searching it in net but coudn't kinda get the answer so can somebody explain it to me...

And since am newbie to the engineering terms pls make the explanation easy and simple...

 

[JaredJames]

Well firstly, you can't extrude that shape, there must be at least one join (which there is).

Which then leads to why in the center?

Well the weak points on a pressurised cylinder (as with aircraft) are the ends. So by ensuring the ends are one complete piece of metal (no joins with the main body) you get the best and simplest structural design for presurisation.

 

[pbaero222]

Thank you jared james...!

 

[Averagesupernova]

I don't think the two ends NEED to be welded together. It is just a cost effective way of doing it that is perfectly safe. It isn't that there is no other way of building them. Larger tanks (500 gal) have each end welded on. Consider an oxygen cylinder for an oxy-acetyline torch. No welds anywhere. When full are at around or above 2000 PSI. The acetyline tank however is assembled like the propane cylinder. There is an insert inside an acetyline tank that the gas is released out of when used. So it would be difficult to assemble one of them any other way.