Rim or edge vents are typically used for internal floating roof tanks (actually, required per API 650 Annex H unless the tank is blanketed or inerted). These are open circulation vents with bird screens, with open area net of the screens of 2 square feet per foot of tank diameter. If all you have are devices that protect the tank from excessive pressure or vacuum (and no internal floating roof), they may be free vents or conservation vents that relieve at a set pressure/vacuum, with our without flame arrestors, see API 2000 for guidance.
If, on the other hand, you are asking about floating roof rim vents, in my humblest of opinions, these have little to no value as there tends to be little to no pressure or vacumm in the rim space given the fact that the seals are not pressure tight.
