Is my assumption correct that it is not possible to meet the frangibility requirements for a self supported umbrella type dome roof?
Can anyone confirm or correct me.
I would say it is not possible, given that the minimum slope of a dome or umbrella roof is achieved when the roof radius is set at its maximum allowable...120% of the tank diameter (API-650 5.10.6.1). This gives a slope of about 24.5 degrees with respect to the horizontal. The maximum slope for frangible roofs, 2:12 as noted earlier and from API-650 5.10.2.6, is only about 9.5 degrees.