Lame's Equation can be used, which is an alternate form of the Von Mises-Hencky Equation for Thick Walled Pressure Vessels. You can find several websites by search under those key words.
Also, the University of Tennessee does an excellent job with an Advanced Mechanical Engineering lecture on this subject. The notes are complete with equations and a worked example.
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada