Whait is process in making LPG cylinder?

Every country has a standard to make this kind of cylinders. For example in my country there is a standard to make this kind of cylinders. And this instructions must to be followed by any factory which want make LPG cylinders. For example this kind of factories , must follows the meassures , welding specifications using special process , the steel used under standard for quality , hardeness , etc. Size of cylinders , shapes , according the use, for example household , automotive , industry ,etc. Any use must have a different design. For example you musn´t use the cylinder desingned for automotive in household and so on. If you want to get more specific information about this , you should go to your local office for standars in your country . So every country has an office for standards which is something like a library where only you can find all standards instructions to make a lot of things.. Eg. Automotive , Mechanical , Chemical , Aircraft ,etc... Regards.