Sir,
can we design empty tank (dome) as per API 620?
we have one case where the tank is empty in opertion condition (in all condition), it will have only process equipment inside it.
This tank is provided only to cover up all the process equipment
Whether API620 allows this case to design?


Regards.

API standards are voluntary & are meant for the convenience of users and suppliers. You have to enquire with state/local authorities whether this is acceptable.