Don't take the risk. You need expertise to calculate and design the pressure vessel and qualified welder to weld the pressure vessel tank. Safety is the main concern to use the pressure vessel.
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Management is just like a bunch of Monkey sitting on a tall tree. Some climb to the highest branch and some at the lowest branch. The highest Monkey look down and see a lot of happy faces but the lower Monkey looks up and see nothing but all the....
You'll need some engineer to be the technical responsible for it anyway. Of course, no one would do it without making the required calculations. If you need to hire someone to do so, then, just let him/her do his/her job.
Pressure vessels are really critical. The professional that is going to do that will know the standards to follow.