Dear All,
API STD 2000 is not applicable to external floating roof tanks is a given. Hence the external floating roof tank working and standing losses cannot be calculated based on API 2000. My understanding is API 42, Chapter 7 needs to be used for tank vapor losses and thus for sizing of VRU irrespective of tank configuration. Also, VRUs are never sized for thermal outbreathing calculations as given in API 2000. Working losses (liquid filling) also need to be calculated as per API 42, Chapter 7.
Can somebody corroborate my understanding?
Regards,
Ankur.