Defines whether API 650, API 620, or API 653 rules are applied to the current job file. Select the entry from the list. Based on the design code that you select, the software displays different fields in other sections of the TANK input.
API 650 and API 620 are intended for the design of new tanks and can be implemented
in either design or analysis modes. Because API 653 is intended for the analysis of existing tanks, it can only
be used in analysis mode.