Hi, We have a steel tube made of a material with yield limit 1000 N/mm2. It is 250 mm long, outside diam. is 76 mm, inside diam. is 60 mm. It is plugged at both ends. Inside pressure is nearly 0 (zero) and outside pressure due to submersion is 69 MPa (MegaPascal). Will this be safe? How can I calculate what pressure that would be 'catastrophic' for the pipe?