wind girders for internal floating roof tanks

[ghkskn]

As far as I understand API650 requires top and intermediate wind girders ONLY for "open-top" tanks. Is there any rule mandating the use of intermediate wind girders for tanks with internal floating roofs.

Gokhan

 

[JStephen]

API requires top wind girders for open top tanks. Intermediate wind girders are required for fixed roof or open top tanks only when the shell thickness is inadequate for wind resistance. In many cases, it is cheaper to use a thicker shell than to do the extra welding on the intermediate wind girder.