Shabeer,

Remember that the aim of the blast analysis is to make sure that the system maintain the integrity after a explosion event. So if the pipe maintain integrity but the equipment not.........

Plastic deformation is acceptable because nobody expect to continue to operate the plant after an explosion, but mechanical integrity must be maintained (for the selected systems). As previously said, also leakage check (including at the flanges connected to equipments) is also required so in some cases this will be the limiting factor.

Regards,