External pressure calculations for Supported Conical roof

Hello,


I am designing one tank which is supported cone roof. That needs to be designed against external pressure as per Appendix V of API 650. In that, all the equations are shown only for self supported cone/dome/umbrella roof.

Does it mean that external pressure calculations are not needed for supported roofs.


Thanks in advance for your earlier response.


Raja.

Hello,


I am designing one tank with internal pressure as atmospheric + full of liquid as per API 650.

Generally, tanks under 18 kPa internal pressure falls under this code category.

Anyone please tell me what will be the exact internal pressure value for atmospheric tanks??

Initially i assumed zero pressure by considering the tank is operating under atmospheric conditions. But while doing this, the required roof to shell junction value (as per appendix F) comes as negative value.

Now i considered 0.75 kPa after referring some tank guide books. Please tell me that the considered internal pressure value is correct??


Thanks in advance for your response.

Raja.