Calculating maximum external pressure on a steel pipe

[Henkobus]

Hello,

I need to make a strong casing for an underwater sound recording device. The casing has got to have a minimum inside diameter of 80mm and a length of 350mm. It has to be functional at an external pressure of 500psi, it is going to operate a maximal depth of 300 meters.
What is the best way to calculate the required wall thickness of the pipe to be strong enough?

Thanks in advance

 

[MFJewell]

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